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flyboy3b
29-11-2007, 06:48 PM
what would you consider a "too high" pressure for a medium temp unit using 404a?
the pressures im working with are 65psig and 325psig with an ambient temp of 70f. the liquid line is hot (around 115f), the superheat is a tad under 30 but the unit is still coming down to temp.
i built this cooler (a small, glass door wine cooler) from scratch and it has a new condensing unit (404a, med temp 1/4 hp) and im just not sure if i got the charge right.
i discovered a small leak at one of my flare fittings and repaired that then this morning i pumped it down and pulled a 200 micron vacuum and refilled it with 10 oz of liquid. i slowly brought the charge up by 1/2 oz at a time up to 12.5 oz. them air temp at the evap coil was coming down slowly (46f) last i checked.
this box is less than 20 cubic feet and i think the temp should be dropping alot faster considering the size of the condensing unit.
also,,, there is a new txv and drier installed.
any suggestions will be appreciated,
thanks,
mike

Gary
29-11-2007, 08:10 PM
It isn't about pressures, it is about temperatures.

For starters, we need to convert the pressures to temperatures using a P/T chart.

65psi = 26F Saturated suction temperature (SST)

325psi = 123F Saturated condensing temperature (SCT)

123F saturated condensing temp minus 70F ambient temp gives us a condenser TD of 53F. This is excessive and tells us that the condenser cannot handle the load. We need to find out why.

Measure the temperature of the air entering the condenser and the temperature of the air leaving the condenser, then subtract entering air temp from leaving air temp. The result is the condenser delta-T aka dT. If the dT is more than 30F, then the airflow through the condenser is insufficient.

If the airflow is sufficient, subtract the liquid line temp (near the condensing unit) from the SCT. The result is the condenser outlet subcooling. If the subcooling is more than 15F, there is too much refrigerant in the high side of the system, backing liquid up into the condenser, reducing its ability to reject heat.

Your current numbers show subcooling of 123F - 115F = 8F. This is far from excessive, but we should always check dT and correct any airflow problems before checking subcooling. Airflow can and will effect subcooling.

Let us know what you find, each step of the way.

flyboy3b
29-11-2007, 09:07 PM
gary,, thank you for your quick reply,,,

heres the skinny,,, about an hour ago,, i went down to check on the progress and the box temp was at 44.7f and the pressures were 57 and 300. so i added 1.2 oz of liquid (bringing me up to 13.7 oz) and that brought the high side up to 325 again and the box temp started to drop some more.
after i read your post,, i went back down to get the temps you asked for and here is what i found.
box temp 42f
suction line temp 47.4f
air going into the condenser 91.1f
air leaving condenser 99.6
pressures at 56 and 325 psig
i honestly feel that i could add another ounce, but im not used to seeing such high head pressures (im not used to seeing ANY pressures as i am still new to this trade).
admittedly, i could use some cooler air entering the condenser coil. this unit is in a box with one side open to the air and a hole (approx 12"x12") on the other side for air to enter the condenser coil. as i mentioned earlier,, its a brand new unit (new old stock) and the cond coil is shiny new and nothing seems too hot to touch,
and the superheat is still around 27.
again,, many thanks for your time,
mike

taz24
29-11-2007, 09:54 PM
and the superheat is still around 27.
again,, many thanks for your time,
mike

Have you put a liquid sight glass in the line before the TEV (TXV).
If you have charge the system till it clears.

taz.

Gary
29-11-2007, 09:54 PM
123F SCT minus 91F air in = 32F condenser TD, which indicates heavy load, but not excessive.

56psi = 20F

42F air in minus 20F SST = 22F evaporator TD, again heavy load but not excessive. With heavy load comes high superheat, as we saw in your other thread.

100F air out minus 91F air in = 9F condenser dT, indicating excellent airflow.

Similar air in and air out measurements on the evaporator would give us the evap dT, indicating evap airflow, although the heavy evap load says that the airflow is probably sufficient.

That brings us to the condenser outlet subcooling (SCT minus liquid line temp) and the evaporator outlet superheat (suction line temp minus SST).

If the condenser outlet subcooling is above 15F, you have added too much refrigerant.

Gary
29-11-2007, 10:17 PM
Note: The difference between liquid line temperature and air out temperature is the condenser approach. Given sufficient airflow and normal subcooling, high condenser approach would indicate a thin insulative coating on the condenser tubes, generally resulting from carbon deposits in high (automotive) traffic areas accumulating over long periods of time. But this being a new system, we can safely ignore the condenser approach temp.

Similarly, evaporator approach can indicate coating of the evaporator tubes, such as oil coating the inside of the tubes caused by oil logging.

flyboy3b
29-11-2007, 10:27 PM
gary, thanks again, i will watch it over the next day or two and see how it does. at nighttime,,, the bartenders are in and out fairly often, so it will have a hard time maintaining temp, but by morning, it should be stableized and i will check it then.
in the meantime,, i will see what i can do about getting some cooler air across the condenser coil.
taz,,, i appreciate the help, but the last system i worked on had a site glass and when i found (what i thought) were the optimal settings for that machine, there were bubbles in the glass.
thanks,
mike

Gary
30-11-2007, 12:09 AM
By definition, if the superheat is right (at design room temp), you have enough refrigerant in the system to do the job. However, solid liquid entering the TXV will help to prolong its life.

Therefore, when everything else is right, it is a good idea to slowly add a small surplus of refrigerant until the sight glass clears or the subcooling is 15F, whichever comes first. This is the optimum charge.

The manufacturer's recommended charge gives us a quick easy way to charge the system close to optimum, which is an important consideration when you are charging the customer for your time. It is "close to optimum" because just as identical twins have subtle differences, no two systems are truly identical, much less hundreds of identical systems coming off an assembly line.

REEFER-TEK
02-12-2007, 07:31 AM
Liquid line seems a bit hot and the head pressure seems a high for ambient, as gary said above you need to use the pt chart to determine what the no normal pressures are, I have always used a simple formula that calculates normal or close to normal high side pressure.

Most condensors operate at a close to estimated temperature of 30 degrees over ambient. So if we know what are ambient is and add 30 degrees to it we can safely estimate, by this simple formula

70 degree ambient +30 degrees= 100 degreesF
100 degrees f for R-404a on a pt chart= 235psi

Normal estimated press is 235 +/- 25 psi

The normal head pressure should be between 210-260 psi. and you are at 325.

I think we have definetly determined your high side pressure is above normal.

Lets take a look at the suction pressure similiar as above excecpt normal operating sytems have an average coil temp of 15 degrees f below temp controlled area.

I believe you said return air temp of 42 degrees f.

take 42 degrees subtract 15= 27 degrees f
27 degrees f for 404a on a pt chart= 60 +/- 5 psi

normal estimated suction pressure 55-65 psi
you are running the proper pressures base on info you put above

now we can go the next primary symtom hot liquid line, liquid lines if the condensor is working correctly in releasing the heat should have a temperature of 10 degrees over ambient. your units liquid line had a tempertaure of 100 degrees +. this indicates there is no transfer of latent heat of condensor, Now we need to looka the secondary symptoms what is in the liquidline sight glass, is the glass clear of bubbles?

REEFER-TEK
02-12-2007, 07:47 AM
got cut off,

any way based on the symtoms i would guess that you have non condesables (air or nitrogen) trapped in the system, or you have a overcharge.

As gary said there are specif weights that manufacturesrs use but does not necessarly mean that holds true to your unit. You will best off performing a controlled charge of the sytem.

If you have a recovery machine with recycler you may determine if there is non condensables with the the recovermachine gauges based on estimates i gave you on top.

I hope this info is helpfull. I would be curious as to what you find as well.

Regards R-T

coolhibby1875
02-12-2007, 02:00 PM
hi i think i would increase the size off the orrifice in your exp valve

taz24
02-12-2007, 06:03 PM
taz,,, i appreciate the help, but the last system i worked on had a site glass and when i found (what i thought) were the optimal settings for that machine, there were bubbles in the glass.
thanks,
mike


With some refrigerants that is somtimes the case.
As with all things the sight glass is just a tool to be used with all the other tools available.
With experience the engineer should be able to tell the differance between flash gas and normal opperating conditions.

taz.

REEFER-TEK
02-12-2007, 06:20 PM
It just occured to me, that you are using R-404a refrigerant in a medium temp application, R404a works more optimal in deep frozen applications.

If you are wanting to maintain temps of say 32 degrees and above you should, consider r-134a or R- 407c as the refrigerant to be used. It would be the optimum refirgerant for medium temp applications.

Where R-404a is more optimal for use at tempareatures lower than 32 degreesF.

If this was done you will have to change the TEV/TXV and pressure switches to accomodate new operating pressures, along with the necessary compressoir oils that are empolyed with there specific refrigerants.

Just my opinion.

Regards R-T

Gary
02-12-2007, 06:34 PM
any way based on the symtoms i would guess that you have non condesables (air or nitrogen) trapped in the system, or you have a overcharge.


Based on the original numbers, I might be inclined to agree with you, except for the fact that the subcooling was not excessive. This tells us that the there are no noncondensables, nor is the system overcharged.

The 'condensing temperature over ambient' rule assumes that ambient air is entering the condenser. Upon measuring the temperature of the air entering the condenser, we find that this is not the case. The entering air temp is 91F, not 70F. 91F + 30F = 121F, which is very close to 325psi.

Either the condenser is in a warm area, heated air is being blown towards the condenser from another unit, or the condenser discharge air is recirculating.

Flyboy3b is apparently aware that he needs to do something about the warm air entering the condenser.

Given the very heavy load on the condensing unit, the one thing I am absolutely certain is NOT the problem is... TXV orifice size.

REEFER-TEK
02-12-2007, 07:29 PM
Based on the original numbers, I might be inclined to agree with you, except for the fact that the subcooling was not excessive. This tells us that the there are no noncondensables, nor is the system overcharged.

The 'condensing temperature over ambient' rule assumes that ambient air is entering the condenser. Upon measuring the temperature of the air entering the condenser, we find that this is not the case. The entering air temp is 91F, not 70F. 91F + 30F = 121F, which is very close to 325psi.

Either the condenser is in a warm area, heated air is being blown towards the condenser from another unit, or the condenser discharge air is recirculating.

Flyboy3b is apparently aware that he needs to do something about the warm air entering the condenser.

Given the very heavy load on the condensing unit, the one thing I am absolutely certain is NOT the problem is... TXV orifice size.


Gary, I was basing my opinion on the first topic posted, I would agree that if he has 90 degree air entering the condensor the numbers do look more right.

I should have probably read more thorouhly, The condensor must be located in a horrible spot if he has 70 degree ambient with 90+ degrees entering it.

again my apologies.

Gary
03-12-2007, 09:04 AM
There's no need to apologize. We all miss things sometimes, myself included. The devil is in the details.

flyboy3b
05-12-2007, 01:42 AM
again,, i say thanks to you folks for all your input. let me clarify a few things first,,,
i built this cooler from scratch,, so i dont really have an idea of what it needs,, im just trying to find the proper balance for this. i dont know if you guys really wanna know the whole story behind this,, but ill give you the short version... and remember,, this is a new field for me.
ive reconfigured this thing so many times i lost count. i built it in my brothers pole barn which until recently was toasty warm. ive had 3 different cap tubes installed to a point where i thought i had it right (at that point it was a 134a cooler). feeling pretty good about having TUNED my new cooler to perfection, i finished the woodwork and installed the glass and packed it up for installation. by the end of the day, i had it in place,, and it looked grand.
unfortunately it was not cooling very well, lol. so out of desperation,, i took a NOS (new old stock) 404a condensing unit i had and swapped out the 134a system. i picked up a TXV (i wanted to be able to freeze this flippin wine if for no other reason,,,than just for spite) and filled it with refrigerant. and that brings us up to date,, more or less.
reefer, there is no sight glass, but i appreciate the input. in case you guys didnt know it,, i write this stuff down that you tell me. its funny,, its all stuff i learned in my classes, but it was harder to remember back then. there is alot to be said for "practical application".
so heres where were at,,,
i brought the charge down to about 260 this morning, and got the txv in about the middle ( i gave up trying to get superheat readings until the system stabilizes) and it actually seems like its doing ok. at least its keeping the wine cold. tomorrow morning i will recheck all pressures and temps and post them here. sometimes i get too impatient and i want things to work NOW. what a different perspective there is a day or two later. unfortunately we dont always have time for that (since this is my own work,, i do not have that pressure)
anyhow,, thanks again. on an even brighter side i got my new fieldpiece datalogger today.

Gary
05-12-2007, 05:01 PM
i brought the charge down to about 260 this morning...

This gives me the impression that you are trying to charge the system by pressure. It doesn't work that way.

Charging by pressures will not get you into the ballpark or even into the neighborhood of the ballpark. Not even the right zipcode.

Saturation pressures are primarily a result of the temperature and volume of the air moving through the coils, having very little to do with the amount of refrigerant in the system.

You need to charge by liquid line subcooling. The proper charge will give you 10-15F subcooling if everything else is right.

Gary
05-12-2007, 05:30 PM
ive reconfigured this thing so many times i lost count.

In your other thread, I gave you a list of the temperatures needed to tune a system.


Low side:

Evaporator air in temp
Evaporator air out temp
Saturated evaporating temp (low side pressure converted to temp from a P/T chart)
Suction line temp at the evap outlet
Suction line temp near the compressor inlet

High side:

Condenser air in temp
Condenser air out temp
Saturated condensing temp (high side pressure converted to temp from a P/T chart)
Liquid line temp near the receiver outlet


That's the easy way. The way you are doing this is the hard way.

Gary
05-12-2007, 06:23 PM
Let's see if we can translate this into an if/then statement for all the computer geeks out there:

If the temperature controls call for cooling and
If the evaporator fan is running properly and
If the evaporator airflow is adequate and
If the condenser fan is running properly and
If the condenser airflow is adequate and
If the compressor is running and
If the subcooling is not excessive and
If the superheat is not too high and
If the superheat is not too low
THEN the system is functioning properly

That's a lot of ifs, isn't it? But that's what it takes to make a basic refrigeration system function properly. On more complex systems the if list can be much longer.

Note that the superheat is at the very end of the list.

flyboy3b
05-12-2007, 06:33 PM
believe it or not,, i think i am getting smarter every day (my gf might disagree with that).
here are the most current readings,,,
ambient 70f
box 43f (pretty much where i want it)
air entering condensor 77

flyboy3b
05-12-2007, 06:43 PM
sheesh,,,,

believe it or not,, i think i am getting smarter every day (my gf might disagree with that).
here are the most current readings,,,
ambient 70f
box 43f (pretty much where i want it)
air entering condensor 77f
air leaving cond 93f
liquid line at receiver 101f
pressure at receiver 280f
liquid line 3" from compressor 160f
suction line after evap 47f
suction pressure 52

so,, what i see is about 27f of superheat and 9f of subcooling. if i am doing my math right,,, 77f into the condensor coil plus 30f equals 110f which is 271 psig. am i right in assuming that the superheat is still a little high?

Gary
05-12-2007, 07:15 PM
Sorry... didn't mean to get preachy.

280psi = 113F
52psi = 17F

113 - 101 = 12F subcooling
47 - 17 = 30F superheat

Open up the TXV one full turn (counterclockwise), wait an hour or so (at least 15 minutes if you're in a hurry), then take new readings.

Hmmmm... I'm wondering how the suction line at the evap can be 47F when it is in a 43F box? It can be colder than the box, but it shouldn't be warmer than the box.

BTW, that hot line (160F) leaving the compressor is called a "discharge line".

flyboy3b
05-12-2007, 07:44 PM
not preachy at all,, i miss stuff all the time. but once i "understand" it,, then i have it.

Sorry... didn't mean to get preachy.

280psi = 113F
52psi = 17F

113 - 101 = 12F subcooling
47 - 17 = 30F superheat

Open up the TXV one full turn (counterclockwise), wait an hour or so (at least 15 minutes if you're in a hurry), then take new readings.

Hmmmm... I'm wondering how the suction line at the evap can be 47F when it is in a 43F room? It can be colder than the room, but it shouldn't be warmer than the room

if i can give you a mental idea of what this cooler looks like,,,, its a 54" wide by 42" tall wall mounted cooler. the cold part is about 42"x42" with 2 glass doors. there is a 12"wide x42"tall part on the right side (like a blind corner cabinet) where the guts are. the condensing unit is at the bottom and the lines feed up to a box that contains the evaporater coil and fan. there is an insulated 5" duct that provides the return air to the evap coil and the evap fan suck the air through the evap coil back into the box. the txv is mounted in ambient air space and the suction line comes out next to it to returns to the compressor. about 6" from the evaporater is where the txv bulb is mounted and where i am taking that 47f temp.

flyboy3b
05-12-2007, 07:51 PM
ps,, i will have to wait till after lunch to do any adjusting,, there is a bunch of stuff i have to move to get access to the txv and high side port

Gary
05-12-2007, 08:01 PM
The TXV and especially the sensing bulb should be mounted inside the refrigerated area. If the sensing bulb absolutely must be mounted outside the refrigerated area, it should be heavily insulated.

Gary
05-12-2007, 08:02 PM
ps,, i will have to wait till after lunch to do any adjusting,, there is a bunch of stuff i have to move to get access to the txv and high side port

I'm retired... I can wait.

flyboy3b
05-12-2007, 09:05 PM
i had to go down and work for lunch,, so i tore it apart anyways,,, here is the latest,,,
its not really feasible for me to mount the txv inside the cooled space,, so i will have to insulate. i figured the worst that would happen is that the txv would overfeed the coil and as long as the pressure was low enough,, the temp would be fine.
anyhow,, one full turn ccw and 30 mins later,,,
evap in 55f (im not real confident on this reading)
evap out 43f
cond in 65f
cond out 90f
suction line after the evap 50f
suction line into compressor 53f
liquid line at receiver 101f
pressures are 55 and 275

Gary
05-12-2007, 09:48 PM
What is the box temperature?

flyboy3b
05-12-2007, 09:58 PM
the box is up to 45f and i just checked the other readings,,,
evap in 49f
evap out 44f
cond in 61f
cond out 87f
suc temp after evap 46f
scu temp before comp 54f
rec temp 98f
rec pressure 280
suc pressure 50
shouldnt the low side pressure have gone up? and yes,, im sure i turned it one full turn ccw

Gary
05-12-2007, 10:36 PM
Why is the cond in temp dropping?

Gary
05-12-2007, 10:43 PM
These temperature readings aren't making sense. What kind of thermometer(s) are you using?

flyboy3b
05-12-2007, 10:55 PM
im using a fieldpiece hs35 meter with a K-style temp probe, i can try my other thermometer later, just to double check, but the fieldpiece is practically new.
as far as the condenser temp,, so,, you can picture the wine cooler we have been discussing,, well, under it is a manitowoc Q-210 (air cooled) ice machine. the ice machine vents out the front,, and the wine cooler pulls its air from the back and also vents out the front. but next to the ice machine in the adjacent wall to the right is the cold air return for the furnace. so,,, im guessing,, sometimes the ice machine is running and the furnace is not,, and that corner warms up, and other times,, the ice machine is off,, and the furnace is on,, helping to ventilate that corner.
anyhow,, its almost 3pm,, and i need to get a nap in before i work tonight. its hell gettin old,, eh?
thanks again,
mike

Gary
05-12-2007, 11:13 PM
Is there a fan speed control or a fan cycling on/off control on the condensing unit? The head pressure seems to be holding remarkably steady with the cond air in temp dropping from 77F to 61F.

Does it actually get to 61F in that corner?

Get a nap... we'll play with it some more tomorrow.

Gary
06-12-2007, 12:11 AM
The fieldpiece should give you accurate readings. When checking line temperatures, strap the end of the probe tightly to the line using electrical tape.

While we are checking out the system, you might want to put the furnace fan control into fan-on position so that the fan runs continuously, equalizing and stabilizing the room temperature.

flyboy3b
06-12-2007, 12:57 AM
i dont think there is any sort of speed control on the cond fan,, what i think it is,, is when i put this 404a cond unit in,, it was bigger than the coil and comp i pulled out,, so i had to cut out the drywall on the left,, and the plaster and lathe in the back. so in the back of the unit is the bare brick from the outside of the building. ive been to clearwater and clearwater beach many-a-time,, and let me tell you,, its fricken freezin up here in this 120 yr old building in wisconsin, lol
and i cant do the fan-only thing, ,cause this building cools down in a matter of hours. what i can do,, is try to keep the conditions as stable as possible and take some more readings. i will check it when i go down to work (i live upstairs) and check it again in the morning.
at this point,,, i am happy that its working at all.
maybe you wanna get out of that hotness and come to wisconsin for a nice winter break. ill buy you and that female next to you a nice dinner.
thanks again,
mike
www.wavespub.com

ps,, that area of florida is one of my favorite parts of the US

Gary
06-12-2007, 05:56 AM
i dont think there is any sort of speed control on the cond fan,, what i think it is,, is when i put this 404a cond unit in,, it was bigger than the coil and comp i pulled out,, so i had to cut out the drywall on the left,, and the plaster and lathe in the back. so in the back of the unit is the bare brick from the outside of the building.

You might try to insulate the brick... even a thin layer of plastic would be better than nothing.

Gary
06-12-2007, 06:11 AM
maybe you wanna get out of that hotness and come to wisconsin for a nice winter break. ill buy you and that female next to you a nice dinner.
thanks again,
mike
www.wavespub.com

ps,, that area of florida is one of my favorite parts of the US

Hmmmmm... winter in Wisconsin... now how could I possibly pass up an offer like that?

My sweetie is from northern Ohio... and I escaped from Detroit... Soooo...

Here's a better idea... come on down. But I have to warn you. The winters are brutal here. This morning, for almost three hours, I had to wear a sweatshirt... brrrrrrr...

BTW, that picture was taken last year at an outdoor Xmas party (hence the festive SantaSkull T-shirt).

flyboy3b
06-12-2007, 11:50 AM
gary,,,,,,,,,,, remember,,, the brick you want me to insulate right now is about 35f. there is no insulation in this old building. the times that the "in" temp to my cond coil is when the outside temp is overtaking the inside temp.
next spring we may have this same conversation, lol

ps,,,i brought my electrotherm digital thermometer down tonight,,, and in most cases,, it was within a degree or two of the readings (side by side) with the fieldpiece.
i wonder how often technicians take so many readings so close together. this is more of a pet project for me,, i guess. my first project.
anyhows,, its 1am and time for bed

Gary
06-12-2007, 05:58 PM
How do the temps look this morning?

Gary
06-12-2007, 06:03 PM
i wonder how often technicians take so many readings so close together. this is more of a pet project for me,, i guess. my first project.


In truth, the average tech takes very few readings and wouldn't know what those readings mean anyway. They fix the obvious problems and never tune the system. If/when it puts out cold air, they take the money and run.

flyboy3b
06-12-2007, 06:12 PM
here is the latest set of measurements,, and i went out of my way to verify them,,,, and for what its worth,, its seems like its doing ok.
box temp 44f
evap air in 55f (still seems high to me)
evap air out 44f (it seems like that should be a little lower as well)
cond air in 65f
cond air out 90f
liq line at receiver 98f
suc line after coil 48f
suc line at comp 63f
pressures at 55 and 280 psig

looking back at my other measurements,, the suction line temp didnt change much after that txv adjustment, in fact,, none of the temps changed much. the txv is still icing up but not excessively. the system is run by a line voltage thermostat (right now i have the bulb a little too close to the evap coil so it turns on and off about every 25 min mins depending on usage).
anyhow,, i have to run out by my brothers house and help him install a snowblower to his john deere and ill check back a little later to see if anybody wants to throw their two cents in.
thanks again,
mike

Gary
06-12-2007, 06:38 PM
I would place the thermostat bulb near the return air duct. That alone should make a big difference.

Set the thermostat to 35F. Let's see what the system does in a "normal" temperature range.

I'm assuming the evaporator fan runs non-stop... even during the off cycle? If it doesn't, it should.

Actually, the numbers look a little better this morning.

Gary
06-12-2007, 07:44 PM
evap air in 55f (still seems high to me)

Actually, it makes more sense... and this is the temperature that the thermostat bulb should be sensing and controlling.



evap air out 44f (it seems like that should be a little lower as well)


Not if the air in is 55F.

Hmmmm... here is a new temperature measurement for you to take: Locate the copper return bends along the side of the condenser. Read the temperature of the center return bend.

Also, measure the temperature of the liquid line near the TXV.

flyboy3b
06-12-2007, 09:45 PM
man o man,, talk about cold and wet. it took us 2 hours to hook up this blower. have you ever looked at the underside of a john deere tractor with a snowblower on it? theres a belt thats about 10 feet long that serpentines through all these pulleys, a bunch of cotter pins and some strange looking arms with pins and holes.
the problem is that neither of us have ever seen it installed and we dont have a manual. anyhow,, all is well,, and the snow is gone.
back to reality,,, gary,,, i bought the thermostat from american scientific (like an army surplus for electronics) for 5 bucks. its a ranco controller and i think it was designed for high temp applications. so i opened it up and adjusted the contacts to close at around 35f giving me about a 10 degree differential. the problem is that i think when i adjusted beyond the design range of the switch,, it through off the sensitivity of the switch. as i move the switch further away from the evap coil,, it takes exponentially longer for it to shut off, causing ice build up on the coil. but yes,, i agree,, it needs to move further away. once everything else is up to snuff,, i will start playing with that.
i will try to get back into the cooler this afternoon. it takes a little time because i have to disassemble the shelves on the cabinet to the right, but we can try another full turn ccw and see what happens.
in the meantime,, im gonna dry out my shoes and try to warm up a bit. there was something else i was gonna say,, but i forgot what it was.
thanks ,
mike

flyboy3b
06-12-2007, 09:48 PM
i just remembered what it was,,,
i can take those temps on the loops, but i have to take a cover plate off to do it and it will read high because of the ambient air entering the evap coil. but the readings should be relative to how much refrigerant is in the coil, sort of.

Gary
06-12-2007, 10:05 PM
Let's cancel the TXV adjustment for now. And the loop measurement I want is on the condenser coil, not the evaporator coil.

Thinking about your surplus thermostat with the 10F differential and just shaking my head. You need a real thermostat... and about a 3F differential.

When you say "near the coil", please tell me you have it sensing coil inlet temperature and not coil outlet temperature.

Gary
06-12-2007, 10:09 PM
man o man,, talk about cold and wet. it took us 2 hours to hook up this blower. have you ever looked at the underside of a john deere tractor with a snowblower on it? theres a belt thats about 10 feet long that serpentines through all these pulleys, a bunch of cotter pins and some strange looking arms with pins and holes.


Being a city boy, I've never seen the underside of a john deere tractor... but I did kick a charging bull one time... and lived to tell about it... lol

flyboy3b
06-12-2007, 10:54 PM
hey,, i paid 5 dollars for that thermostat, lol. actually,, i do have some other thermostats i can use,, its just that they were designed for switching 25 amps,, and id rather save them for other projects i have. the way its set up now,, it cycles on for a bout 5 or 6 mins,, and shuts off for about 15 to 20 mins.

getting readings off the condensor might be a little harder (its tucked back in there pretty good,, but i will try

flyboy3b
06-12-2007, 11:41 PM
yes,, the evap fan runs all the time,, its my only protection against freeze up.

no,, if i moved the sensing bulb for the thermostat to the return air for the evaporator,, i would have to readjust the contacts back close at a higher temp.

and no,, the john deere is a not like a big tractor,, more like a big lawn mower.

and ive seen alot of bull as well,, but probably not the kind that you mean

Gary
07-12-2007, 03:29 AM
yes,, the evap fan runs all the time,, its my only protection against freeze up.

Don't worry about freeze up.



no,, if i moved the sensing bulb for the thermostat to the return air for the evaporator,, i would have to readjust the contacts back close at a higher temp.


The return air is where the sensing bulb belongs. Why would you have to adjust it?

Gary
07-12-2007, 04:48 AM
Hmmmm... I'm trying to get a mental picture of this system. Apparently you installed an oversized condensing unit. Assuming the airflow is pull through, and we know the airflow exits the front, then the condenser coil must be sticking out the back. And you have it buried in the wall?... so it's getting restricted airflow, but the air is really cold because it is winter. Does that about describe it?

Please tell me I'm wrong and the condenser is not inside the wall.

cristopher_uy
07-12-2007, 07:43 AM
hi Sir flyboy3b,your thread looks interesting and educational i had a great time reading and thanks to Sir gary for such overwhelming exchanging of professional ideas i may say

i am working here in the middle east where ambient temp varies from time to time especially now a days,where it is getting colder,but not as colder than in US,

as young compare to you guys ,LOL,i just encouraged myself to ask question about your thread's query

your Box temp=43f is desirable to you as application call's for it ,in these temp what really problem's you Sir,i mean is/are other components of the system affected,i mean those visible undesirable symptoms like frosting.

thank you very much

cristopher_uy
07-12-2007, 07:53 AM
the reason for asking is that,it seems your desired room temp is quitely near to the point u wanted but
still problems you

hope your scrap designed system will soon works well.

Gary
07-12-2007, 05:03 PM
Okay... here's where we are at this point:

The thermostat sensing bulb should be sensing the return air.

The condenser should be at least 3 inches from the wall. If this means you have to move the ice machine, then move the ice machine.

The unit isn't running long enough to get good readings, apparently because you are concerned about frosting the coil.

The suction pressures are going to run low and the coil is going to frost, because the condensing unit is oversized. Not to worry, it will melt during the off cycle.

Place a glass of water in the middle of the box and stick a thermometer in it. This will tell you the actual product temperature and then you can ignore the box temperature, which seems to be close to the evap air out temp for some reason.

Are we making any progress this morning?

Gary
07-12-2007, 05:40 PM
BTW, I can understand saving money by doing the job yourself. What I can't understand is using junk parts, which are not even designed for this type of system, from the surplus store. Get a real thermostat.

There is a time to be tight and a time to be right.

markacs
08-12-2007, 07:22 AM
I Am Sure That The Unit Tev Is Too Small And There Is Far Too Much Gas In That System.
Check The Sub-cooling And Check The Superheat!change The System To Cap Tube!!!
325 Psi At 70f.you Will Murder That Compressor If That Ambient Temp Goes Up!too Much Gas Backing Up In The Condenser.

flyboy3b
08-12-2007, 06:14 PM
it looks like i wont be able to get those readings till tues or wed. me and my girlfriend are heading out for a couple days,, just to get out of town,, maybe sit in a hot tub for a while,, have a nice dinner or two,, and try to warm up.

flyboy3b
08-12-2007, 09:01 PM
Hmmmm... I'm trying to get a mental picture of this system. Apparently you installed an oversized condensing unit. Assuming the airflow is pull through, and we know the airflow exits the front, then the condenser coil must be sticking out the back. And you have it buried in the wall?... so it's getting restricted airflow, but the air is really cold because it is winter. Does that about describe it?

Please tell me I'm wrong and the condenser is not inside the wall.

the condenser is 2" from the wall, and i also opened up the wall to give it some extra space and yes,, the condensing unit is oversized, but at the time i needed to get it running and thats all i had on hand to get it working. at some point when i have more time,, i will reinstall the old system with a cap tube.
remember,, i have never built a system from scratch before,, so i just went with what i knew (or thought i knew) and it has been a good learning experience for me.

as far as the thermostat goes,, its not a "cheap" thermostat,, i just didnt pay alot of money for it. its a ranco thermostat and it is adjustable. give me a few days and ill go in and move the sensor bulb and adjust the differential down.

markacs,, the txv is a 1/4 ton and it should be plenty big for a little box like this,, but i agree,, it should be a cap tube system. it started out as a cap tube systm.
thanks for all the input,, ill see you folks in a few days,
mike

keithholstead
12-12-2007, 03:11 PM
I'm sorry but as 404a is a blend of refrigerants you cannot charge to a full sight glass, due to the fact that some vapor is always going to be present. This is quoted from Althouse. Turnquist, et. al., and also known from experience.

flyboy3b
12-12-2007, 05:12 PM
hi honey, im hooome,

man,, we ended up driving back through that ice storm yesterday. it wasnt as bad in wisconsin as it was elsewhere, but it sure was slippery, and the snowflakes in milwaukee were 2" wide. crazy stuff.

so,, here is where we are today.
i moved the thermostat bulb to the inlet of the evap coil and adjusted the thermostat. these are the current readings (taken before i moved the thermostat)

ambient 74f
box temp 47f
cond air in 74f
cond air out 90f
evap air in 56f
evap air out 42f
suc after the evap coil 53f
suc at compressor 62f
liquid at receiver 98f
pressures 52/278 psig

ive included a couple of pictures (if they arent too large to post) so you can get an idea of what this thing looks like. if i could ask a favor,,, gary,,,, would you apply your magic formula to these measurements and post the results?

ok,, the pictures were too large,, so i posted them to my website,, and i will try to include the link here,,,
http://wavespub.com/cooler.html
lets hope this works,
thanks again
mike

Gary
12-12-2007, 09:22 PM
Wait until the evap air in is 40F or less, then take measurements. If the unit shuts off before the evap air in gets below 40F, then the thermostat isn't set low enough.

BTW, I don't think you could pick a worse location for that condenser. Judging by the picture, its a wonder that it gets any airflow at all.

flyboy3b
12-12-2007, 09:58 PM
i dont think the evaporater return air will ever get that low,, but what the heck,, i have time. maybe next monday when no one is going in there.

flyboy3b
12-12-2007, 10:02 PM
and yes,, i agree,, the condenser coil is in a bad place,, but ill make sure it gets the air it needs. the restaurant is very small and there is no basement. you would be shaking your head even more if you knew where all my remote condensing units were and how i keep them cool.

Gary
12-12-2007, 10:47 PM
I take it the thermostat is located inside the box? The thermostat can be located anywhere that's convenient, as long as its sensing bulb is located in the return air. For example, you might want to locate it in the machine compartment on the outside of the evap cover plate.

Gary
12-12-2007, 10:58 PM
and yes,, i agree,, the condenser coil is in a bad place,, but ill make sure it gets the air it needs. the restaurant is very small and there is no basement. you would be shaking your head even more if you knew where all my remote condensing units were and how i keep them cool.

I've been shaking my head for forty years. Nothing surprises me anymore. Let me guess: They are in a crawl space under the building, sitting in the mud... or maybe up in the attic, roasting in the summer and getting a hernia from the head pressure. Been there, done that.

You might consider turning the entire condensing unit 180 degrees. Room air would enter the condenser from the bottom of the opening and the heated air would then rise and exit out the top of the opening back out into the room.

I hope you aren't planning to put a door on that opening. You would have the hot air recirculating.

flyboy3b
12-12-2007, 11:30 PM
if you look closely at picture of the right side,, you will see and electrical box with some yellow wirenuts sticking out. along the edge of that junction box, in the middle, you will see a brass knob. that is the thermostat.

all the pipe connections are on that end of the condensing unit,, turning it around would be a real nightmare to install or repair, but its a nice idea.
ideally,, i would have one or two remote units in the basement, and just pipe everything from there,, but its not possible

Gary
13-12-2007, 04:35 PM
ambient 74f
box temp 47f
cond air in 74f
cond air out 90f
evap air in 56f
evap air out 42f
suc after the evap coil 53f
suc at compressor 62f
liquid at receiver 98f
pressures 52/278 psig


52psi = 17F
278psi = 112F

112 - 74 = 38F TD. This shows a very heavy load OR non-condensables. I believe it is heavy load because the subcooling is not excessive (112 - 98 = 14F subcooling), but I could be wrong.

We can check for non-condensables by pumping down the unit and comparing the high side pressure to the temperature of the condenser.

Close (front seat) the receiver outlet valve. When the low side pressure reaches around zero psi, shut off the unit. Let it sit for about 15 minutes, then measure the temperature of the condenser. Insert your temperature probe between the fins near the center of the condenser.

We will need to know both the condenser temperature and the high side pressure.

BTW, do you have a pressure/temperature chart? They give them away at refrigeration supply houses everywhere.

Or here is an online chart:

http://www.parker.com/rs/PDFS/Ref_Temp_Chart.pdf

flyboy3b
13-12-2007, 09:47 PM
ill do the pump-down thing tomorrow morning. i havent taken any temps down there,, but it looks like the box temp has dropped to the low 40s.

i would be surprized if there was any non-condensibles in there as i pulled it down to a 500 micron vacuum last time and the system itself has never run into a vacuum, but what the heck,,, it cant hurt to look.

and yes,, i grabbed a bunch of those little charts. handy little devils. i wonder if i can find a software for that to put on my cell phone?

flyboy3b
14-12-2007, 05:16 PM
its me again,,,

i took these readings before i pumped it down,,,

amb 79f (this number can be misleading because at the time, both the ice machine and wine cooler were on. if you took the reading from the middle of the room,, it would be closer to 70f)
box temp 44f
evap in 52f
evap out 37f
cond in 70f
cond out 90f
suc line after evap 44
suc line before comp 56f
liq line at receiver 100f
pressures 45/280 psig

i closed off the receiver valve and it pumped the low side down to 0 psig in less than a minute. i shut the cooler off and waited for about 25 mins. at that time the temp in the cond coil was 66f and the pressure was 180psig. now i know what you might be thinking,,,,,, 66f would indicate a pressure of 138 psig for 404a,,, quite a difference from 180 psig. and im not saying that it would be impossible for there to be non condensibles in the system, but,,,,,, the temperature at the cond coil may be reading falsely wrong because when everything is off,, the adjacent (outside brick) wall would bring that temp down fast. the compressor was still warm (maybe 90f) so maybe the true temperature is somewhere in between those numbers. the low side pressure remained at 0 psig the whole time.

one question i would have is,,,,, if i somehow fractionated the refrigerant when i put it in,, how much of a pressure difference could i expect to see. i was unable to find a P/T chart for 143a or hfc 125 (the major components of 404a).

anyhow,,, thats where we are.
thanks,
mike

hendry
14-12-2007, 05:25 PM
flyboy3b
1]your design is aircooled chiller.
2]insufficient subcooling @ condenser.
3]wrongly select xpansion valve

if you look into the above you'll have better cooler box.

Gary
15-12-2007, 07:16 AM
i closed off the receiver valve and it pumped the low side down to 0 psig in less than a minute. i shut the cooler off and waited for about 25 mins. at that time the temp in the cond coil was 66f and the pressure was 180psig. now i know what you might be thinking,,,,,, 66f would indicate a pressure of 138 psig for 404a,,, quite a difference from 180 psig. and im not saying that it would be impossible for there to be non condensibles in the system, but,,,,,, the temperature at the cond coil may be reading falsely wrong because when everything is off,, the adjacent (outside brick) wall would bring that temp down fast. the compressor was still warm (maybe 90f) so maybe the true temperature is somewhere in between those numbers. the low side pressure remained at 0 psig the whole time.


Another possibility is that your gauge is off by about 40psi, although that seems highly unlikely. Just to make sure, hook your gauge up to your refrigerant jug. The pressure should correspond to the temp of the jug.

Most likely you have air in the system and you will need to evacuate it again. Did you evacuate from both sides? Did it hold vacuum?

Gary
15-12-2007, 07:29 AM
the temperature at the cond coil may be reading falsely wrong because when everything is off,, the adjacent (outside brick) wall would bring that temp down fast.

You might try placing a piece of cardboard between the condenser and the wall to block the cold air, then check temp and pressure.

Or better yet, measure the temp on the drip leg (the line between the condenser and the receiver).

flyboy3b
16-12-2007, 01:57 AM
i dont actually recall if i pulled a vacuum from both sides or not, but its such a small system,, do you think it would matter?

i held the vacuum for about 10 minutes at 500 microns, i even tapped the side of the compressor,, just in case. but it is a new system,, and i have leak-checked it a couple of times. but like i said before,, the system has never run into a vacuum, so if it were leaking,, the pressure would be dropping (instead of sucking air).

my bottle of 404a is sitting outside, and its cold out,, but i should be able to check my guages with it. i have several other guages to try as well,, but these are the newest.

hendry, i appreciate your input. yes,, its an air cooled wine chiller and i agree,, i could use some more air across the condenser coil. at a point,, im going to have to live with a less-than-efficeint cooler, because that is the only location it can go (its a very small place). the txv, however, is a 1/4 ton, 404a txv. it should be plenty big for this small box.

anyhow,, ill post the latest results later tonight or tomorrow morning.
thanks again,
mike

flyboy3b
16-12-2007, 05:31 PM
ok,, heres the deal,,,

it would appear that gary is much smarter than he looks (just kidding gary).
i checked my gauges against my bottle of 404a i brought in from outside. it is 26f and my high side gauge read 150 psi. well,, thats not right. so i checked the low side gauge and it read 65 psi. that sounds more like it.

i purged the gauge set and retook the readings and both sides measured about the same (correct) pressure .

i double checked this against my bottle of 134a and both sides measured correctly

what do i gather from this? is the lossless fitting not letting the gas back out of the high side fitting? is there something in the high side of the gauge set thats not letting the pressure equalize? is this normal for a REFCO set of gauges or are they broke. this wine cooler is the only system ive worked on in the last week,, so i had no reason to purge the gauge set each time i used it. and why does the low side equalize properly each time? the fittings are the same and they are all brand new.

thanks again gary for your sage and intuitive advice.
mike

ps,, i will retake the readings tomorrow when the restaurant is closed

hendry
17-12-2007, 04:44 AM
i dont actually recall if i pulled a vacuum from both sides or not, but its such a small system,, do you think it would matter?

i held the vacuum for about 10 minutes at 500 microns, i even tapped the side of the compressor,, just in case. but it is a new system,, and i have leak-checked it a couple of times. but like i said before,, the system has never run into a vacuum, so if it were leaking,, the pressure would be dropping (instead of sucking air).

my bottle of 404a is sitting outside, and its cold out,, but i should be able to check my guages with it. i have several other guages to try as well,, but these are the newest.

hendry, i appreciate your input. yes,, its an air cooled wine chiller and i agree,, i could use some more air across the condenser coil. at a point,, im going to have to live with a less-than-efficeint cooler, because that is the only location it can go (its a very small place). the txv, however, is a 1/4 ton, 404a txv. it should be plenty big for this small box.

anyhow,, ill post the latest results later tonight or tomorrow morning.
thanks again,
mike[QUOTE][/QUOTE

thank you to you, too!

you know ... you could modify the condenser to be more efficient with current constraints.

i've done it for my clients.

it became a hybrid condenser. you know what?
lesser condensing pressure/temp & better performance.

worth trying if you are in for better system.

Gary
17-12-2007, 11:50 PM
it would appear that gary is much smarter than he looks (just kidding gary).

I'm not as stupid as I look... nobody is... lol

flyboy3b
18-12-2007, 06:26 PM
here we are again,, and here are the current readings.

ambient 75f
box temp 39f
evap air in 50f
evap air out 41f
cond air in 68
cond air out 81f
suction line at txv 52f
suction line at comp 68f
liquid line at receiver 91f
i closed the receiver valve and pumped down the system and the temp at the condenser was 80f and pressure was 190 psig which is about 15 lbs high,, but that may have balanced out had i waited a bit longer.
when i took these readings the pressures in the system were 55/200 and i suspect a small leak. i leaked checked it again and found no leaks,, but i have not checked either of the coils. next monday
i will recheck the pressures and leak test the other parts if needed. in the meantime,, i topped it off with a couple of ounces of 404a.

hendry,, what modifications are you reccomending?

Chicharronne
18-12-2007, 07:19 PM
I do a mostly reataurants and if you're chilling fancy wines then the mean temp is around the low 50's. I've done several cases that have heater to bring the temp up.
as for 404a, I used to do a lot of Wendy's. they used hobart reach in freezers for french fries. My job was to go behind the other guys reluctantly doing food service(HVAC guys who thought they were too good) I had a unit this guy worked on that had 2 9' cap tubes he replaced then walked away without checking. unit running low pressures. I pressurized to 125psig with nitro and leak checke. pressure held the entire time. weight the charge in and still low pressure. called the factory about the caps. they were correct. factory tech said if the unit was in an area with an ambient temp higher than 78 then the oil seperates from the refrige and coats the inside of the evap. the unit was next to the fryers. I added a couple ozs and temp dropped. they make a flush I have used on other fry freezers since.

flyboy3b
18-12-2007, 07:28 PM
factory tech said if the unit was in an area with an ambient temp higher than 78 then the oil seperates from the refrige and coats the inside of the evap. the unit was next to the fryers. I added a couple ozs and temp dropped. they make a flush I have used on other fry freezers since.

i am aware of the oil problem,, i dont think the temp has been high enough for that to happen,, plus the fact that it is a new system. but i will keep it in mind as a possible problem. i keep the temp down in the wine cooler partly because people are in and out of it all day and the temp rises fast.
thanks,
mike

Gary
18-12-2007, 09:04 PM
here we are again,, and here are the current readings.

ambient 75f
box temp 39f
evap air in 50f
evap air out 41f
cond air in 68
cond air out 81f
suction line at txv 52f
suction line at comp 68f
liquid line at receiver 91f

when i took these readings the pressures in the system were 55/200

55 = 19F
200 = 89F

Well... that changes everything... and it explains everything.

89 - 68 = 21F TD

Light load... and we can forget about non-condensables.

52 - 19 = 33F superheat

89 - 91 = -2F subcooling

You have low subcooling (not enough refrigerant in the high side) with high superheat (not enough refrigerant in the low side). That combination tells us the system is undercharged. Add refrigerant until the subcooling is 10-15F. Then we will see some very different readings. It helps to have accurate gauges.

flyboy3b
18-12-2007, 10:12 PM
lol

ill try to check the subcooling this aft,, otherwise in the am

Gary
19-12-2007, 04:11 PM
i keep the temp down in the wine cooler partly because people are in and out of it all day and the temp rises fast.

Right now it is working reasonably well despite being grossly undercharged with a maladjusted TXV. Once we get this thing working right, you will be able to set the temp wherever you want and it will hold no matter how often people are in and out of it. The TXV will give you very fast recovery. That's what a TXV does best.

flyboy3b
19-12-2007, 05:37 PM
well,,, there is trouble in paradise.

the system has a small leak,, and im not sure where it is. ive leak tested everything accessible and no luck. itll probably be monday before i can get at the 2 coils.

when i went to adjust the subcooling i noticed the box temp had climbed to 52f, so i checked it over and decided to just pump it down and start over. after evacuating the system i hooked up my vacuum pump and started pumping it down. the vacuum gauge hovered between 400 and 700 microns. when i disconnected the hose going to the cooler,, it promptly came down to 200 microns and when i hooked it back up,, it jumped back to 700 microns. so that rules out the hoses, fittings, vacuum gauge and vacuum pump.
anyhow,, i hope its in the evaporator,,, its much more accessible.

on a different matter,, i asked this question on another thread,, but im still not exactly clear on this,,,
with a standard recovery tank with a liquid port and vapor port,, does the liquid port reach into the bottom of the tank? in other words,, if i want to get liquid to come out,, do i leave the bottle upright and use the liquid port,, or do i invert the bottle and use the liquid port.
sorry if this is a stupid question,, but ive never seen the insde of one of those tanks.

flyboy3b
19-12-2007, 05:39 PM
or can i invert the bottle and use the vapor port?

The Viking
19-12-2007, 05:50 PM
Yes, from the liquid port is a dip tube to the bottom of the bottle.

Gary
19-12-2007, 06:49 PM
well,,, there is trouble in paradise.

the system has a small leak,, and im not sure where it is. ive leak tested everything accessible and no luck. itll probably be monday before i can get at the 2 coils.

when i went to adjust the subcooling i noticed the box temp had climbed to 52f, so i checked it over and decided to just pump it down and start over. after evacuating the system i hooked up my vacuum pump and started pumping it down. the vacuum gauge hovered between 400 and 700 microns. when i disconnected the hose going to the cooler,, it promptly came down to 200 microns and when i hooked it back up,, it jumped back to 700 microns.

That doesn't mean you have a leak. It means you didn't leave the pump on long enough. Refrigerant is absorbed into the oil in the compressor. When you shut it down, some of that refrigerant escaped from the oil and brought up the pressure. The question is, after it came up to 700 microns, did it stay there or did it continue to rise? A leak doesn't stop rising until it reaches zero psi.


on a different matter,, i asked this question on another thread,, but im still not exactly clear on this,,,
with a standard recovery tank with a liquid port and vapor port,, does the liquid port reach into the bottom of the tank? in other words,, if i want to get liquid to come out,, do i leave the bottle upright and use the liquid port...

Yes.

Gary
19-12-2007, 06:58 PM
Hmmm... I don't understand why you decided to evacuate it and start over?

flyboy3b
19-12-2007, 07:03 PM
gary,, i had considered that,,, or the possibility of moisture in the system, but this system is so small. i figured it would have balanced out over a period of 20 or 30 minutes. also considering the rise in box temp (which it had been holding fairly well) and the drop in pressure. it just seems the most likely answer.

monday,, possibly sooner,, i will retake the reading and see where we are at

flyboy3b
19-12-2007, 07:18 PM
i left it at 700 microns for 10 minutes.

when i had the vacuum pump hooked up,, it would hit 400 microns,, and then slowly drift back up to 700,, then back down and up again. isnt it possibly to have a leak so small that it would only leak under extreme vacuum or pressure?
in either case,, i figured it wouldnt hurt to rule out any chance of fractionation or noncondensables.

Gary
19-12-2007, 07:25 PM
I have seen nothing remotely indicating a leak. What this system needs is to be charged up to 10-15F subcooling.

Gary
19-12-2007, 07:27 PM
i left it at 700 microns for 10 minutes.

when i had the vacuum pump hooked up,, it would hit 400 microns,, and then slowly drift back up to 700,, then back down and up again. isnt it possibly to have a leak so small that it would only leak under extreme vacuum or pressure?


No, it isn't. What you are seeing is refrigerant escaping from the oil.

Gary
19-12-2007, 08:10 PM
isnt it possibly to have a leak so small that it would only leak under extreme vacuum or pressure?

Perfect vacuum is something less than -15psi. If it leaks under extreme vacuum, then it will leak at 15psi positive pressure. There is nothing extreme about it.

flyboy3b
19-12-2007, 08:45 PM
and you are probably correct,, but what about the sharp drop in pressure and rise in box temp. it was 39f yesterday,, and 52f today,, and the high side presure was down to 200psig

Gary
19-12-2007, 09:06 PM
and you are probably correct,, but what about the sharp drop in pressure and rise in box temp. it was 39f yesterday,, and 52f today,, and the high side presure was down to 200psig

The high side pressure was probably around 200psi all along, but the gauge was not accurate. There is something wrong with that lossless hose fitting.

I can't see the system from here. I can only evaluate it from your measurements, so those measurements need to be accurate... or at least in the ballpark.

The box temp isn't going to tell us anything until we get the right amount of refrigerant into the system... and even then I would go with the glass of water with a thermometer in it. We don't care what the box temp is, we care what the wine temp is... and I'm betting that the wine temp is closer to evap air in temp than it is to box temp.

flyboy3b
19-12-2007, 09:36 PM
and even then I would go with the glass of water with a thermometer in it. We don't care what the box temp is, we care what the wine temp is.

since you said that, ive been taking the temp of an open bottle of wine from the cooler,, so that part was accurate.
as far as the gauges are concerned, i have been making sure to purge them before taking the readings for the last couple of days, so i believe the readings to be accurate.

im not saying im right, but what else could account for such a large increase in box temperature. it had all night to reach temp and i had the thermostat set to its coldest setting (yesterday, when i looked in the cooler,, i had noticed the temp had gone up a bit, so i turned down the thermostat). the wine was at 39f the last time i checked it,, and this morning it was 52f. and the temp has been dropping since i filled it.

i guess we'll know more tomorrow.

Gary
19-12-2007, 09:56 PM
since you said that, ive been taking the temp of an open bottle of wine from the cooler,, so that part was accurate.
as far as the gauges are concerned, i have been making sure to purge them before taking the readings for the last couple of days, so i believe the readings to be accurate.

im not saying im right, but what else could account for such a large increase in box temperature.

Not enough refrigerant in the system.

I haven't been telling you to add refrigerant because the high side pressure (and therefore the subcooling) has been erroneously saying that it didn't need it.


it had all night to reach temp and i had the thermostat set to its coldest setting (yesterday, when i looked in the cooler,, i had noticed the temp had gone up a bit, so i turned down the thermostat). the wine was at 39f the last time i checked it,, and this morning it was 52f. and the temp has been dropping since i filled it.


What are the subcooling and superheat temperatures, now that you have filled it?

Gary
20-12-2007, 07:24 AM
as far as the gauges are concerned, i have been making sure to purge them before taking the readings for the last couple of days, so i believe the readings to be accurate.


It occurs to me that lossless hose fittings are designed to be used on schrader type valves. If the high side access is not a schrader valve, then the hose won't work properly. If this is the case, switch to a standard hose.

flyboy3b
20-12-2007, 06:59 PM
i can disconnect the lossless fittings,, no biggy there,, itll be tomorrow before i can take any more measurements (me and my sweetie had a little too much rum last night and i overslept).

ps,, i know its hard to try to diagnose a system just by reading all my mispelled words (did i mispell mispelled? it looks funny) anyhow,, i appreciate your time,
thanks,
mike

flyboy3b
21-12-2007, 05:17 PM
i took some more readings this morning,,,

ambient 74f
box 45f
cond in 72f
cond out 87f
liq line at receiver 94f
suc line at bulb 41f
evap air in 54f
evap air out 44f
pressures at 35/250 psig

subcooling is 10f
superheat is 27f

the coil had started to ice up (i had the thermostat set to low) so i shut it down for 15 mins and restarted. at that point the pressures were 50/250 psig. ill check it again tomorrow am,, or sunday am.

Gary
21-12-2007, 05:39 PM
Open the TXV another full turn (counterclockwise). Then add refrigerant until the subcooling is 15F.

At this point we have sufficient refrigerant in the high side (10F subcooling), but insufficient refrigerant in the low side (27F superheat). IOW, not enough refrigerant is flowing through the TXV. This could be due to superheat adjustment OR we may have a restricted inlet screen on the TXV.

Another thing that is bothersome is the evap air in temp. Seems like it should be closer to box temp. I'm wondering if room air is getting sucked into the return air duct... or if the return duct isn't sufficiently insulated.

flyboy3b
21-12-2007, 06:12 PM
can do,
thanks

flyboy3b
21-12-2007, 09:51 PM
i agree about the return air. the duct is only 12" long and it is insulated,, i suppose i could beef it up a bit. as far as air leaks,, its pretty tight.
when i built this cooler,, i figured it would be more than sufficient to cool such a small area. since then,, ive upgraded the (evap) fan size twice. it has a dayton 8" axial fan pulling air through the coil now and it seems to have sufficient air flow.
all in all,, it might be better to suspend the coil and just draw air through it.

Gary
22-12-2007, 05:12 PM
Once we have the subcooling and superheat right, the delta-T's will tell us if there is sufficient airflow through the coils. At this point the airflow seems sufficient.

Gary
22-12-2007, 07:32 PM
i agree about the return air. the duct is only 12" long and it is insulated,, i suppose i could beef it up a bit. as far as air leaks,, its pretty tight.
when i built this cooler,, i figured it would be more than sufficient to cool such a small area. since then,, ive upgraded the (evap) fan size twice. it has a dayton 8" axial fan pulling air through the coil now and it seems to have sufficient air flow.
all in all,, it might be better to suspend the coil and just draw air through it.

Hmmm... I'm wondering if we are getting too much airflow? What size fan came with the coil?... and why was it upgraded?

flyboy3b
23-12-2007, 02:40 AM
What size fan came with the coil?

lol,,, came with??????

when i said i built this thing from scratch,, i meant it. as far as i can tell,, the evaporater coil looks like it came from a recovery machine. i bought 3 of them on ebay and they are new. they measure about 10"wide by 7" tall by 2 1/2" deep. initially, i had a 6" inline duct fan but that was too passive. i moved up to a 7" condenser fan,, but that was pushing the air through the coil and that was inefficient. unfortunately, it was too large to mount in front of the coil. so i picked up the axial fan from,,,, where else,,,,, ebay.
with christmas coming up,, i probably wont be able to get back into that cooler until tuesday.

Gary
23-12-2007, 04:51 AM
Any idea how many CFM that fan is rated at?

flyboy3b
23-12-2007, 05:19 AM
SPECIFICATIONS
CFM 180/200
Voltage 115 AC
Hertz 50/60 cycle
Amps 0.6/0.55
Max. air pressure 0.48" H20
Noise level 52/55 dBa
Ball Bearings
Speed 2650/2950 RPM
5 Blade
Fan blade diameter 5-5/8"
Size 6-3/4" x 6" x 2"

Gary
23-12-2007, 02:17 PM
Dare we assume that the refrigerant enters the top of the coil and exits the bottom?

flyboy3b
23-12-2007, 05:26 PM
Dare we assume that the refrigerant enters the top of the coil and exits the bottom?


ummmm,, nope

i checked it again this morning,, here are the readings,,,

ambient 84f
box temp 46f
cond air in 73f
cond air out 93f
evap air in 53f
evap air out 41f
suction line at bulb 48f
liquid line at receiver 100f
45/280

the superheat is still really high at 37f and the subcooling is close at 12f, so i backed out the txv 2 full turns ccw. after about 20 mins the new readings are,,,

cond in 72f
cond out 96f
evap in 56f
evap out 44f
suction at bulb 49f
liquid line at receiver 101f
50/270
superheat at 33f
subcooling at 9f

i wasnt aware that it made a difference where the refrigerant entered the coil. i dont recall ever learning that part. when i set it up,, i figured it was better to have the liquid enter the bottom and exit the top to help insure that only vapor would be returning to the compressor.

anyhow,, its time to head up to sheboygan to visit my gf's family (fun fun).

Gary
23-12-2007, 07:20 PM
i wasnt aware that it made a difference where the refrigerant entered the coil. i dont recall ever learning that part. when i set it up,, i figured it was better to have the liquid enter the bottom and exit the top to help insure that only vapor would be returning to the compressor.


It makes a BIG difference. Feeding the coil bottom up reduces heat transfer and traps oil in the evaporator. The oil coats the inside of the tubes, insulating them... and the compressor is deprived of lubrication.

You need to reverse the lines. Technically, the refrigerant should enter the coil at the top of the leaving air side and exit the bottom on the entering air side (counterflow)... then the suction line should dip down (to trap oil)... then up to the top (to prevent liquid from returning to the compressor)... then down to the compressor.

And while you have it apart, check the TXV inlet screen to see if it has collected any trash.

m3ae2002
23-12-2007, 11:10 PM
what prefer for lubrication 404a mineral or synthetic oil systems

m3ae2002
23-12-2007, 11:30 PM
lubrication system with 404a mineral or synthetic oil which prefer

Lowrider
23-12-2007, 11:36 PM
shouting won't get you helped any sooner!

The oil type depends on sort of compressor, refrigerant type and working temperature!

flyboy3b
24-12-2007, 12:36 AM
what prefer for lubrication 404a mineral or synthetic oil systems

honestly,, i couldnt tell you. this unit came with oil. i would check with the manufacturer of that particular compressor or go to dupont.com and look there.

flyboy3b
24-12-2007, 12:39 AM
You need to reverse the lines. Technically, the refrigerant should enter the coil at the top of the leaving air side and exit the bottom on the entering air side (counterflow)...



ill try to do that on tuesday morning. im not sure if ill be able to flip it around to get the orientation right. time will tell

flyboy3b
25-12-2007, 09:20 PM
ok,, i got it switched around. i was not able to get the counterflow right though. it enters the incoming side and exits the center. and let me tell you,, it was a real bugger getting in there to sweat those joints. ill be very happy if it doesnt leak.

before i pumped it down,, i did find a small leak from an access fitting which i tightened. i believe that was part of the problem initially, but we will see.

anyhow,,, i added some new 404a liquid and brought the pressures up to 50/250. at that point the liquid line at the receiver was 89f which gives me a subcooling of 15f. the txv was frosted and the unit sounded normal.

condenser air in 70f
cond air out 85f
evap air in 59f
evap air out 50f
suc line at bulb 49f and dropping.

it took me a couple hours to do the work,, and the box warmed up,, so ill check it later tonight and see how the superheat looks.

the txv screen was clean

flyboy3b
26-12-2007, 05:23 PM
i checked it last night and took these readings,,,

liquid at receiver 94f
suction at bulb 49f
evap air in 51
evap air out 47
cond air in 70f
cond air out 85f pressures at 45/255 psig

the coil was pretty frosted up so i shut it down for 15 mins and cranked the txv back 2 turns ccw. this morning it was not frosted up,, but the box was a tad warm, so i turned it back 1 turn cw. the readings at that point were,,,

suction at bulb 51f
liquid line at receiver 95f
evap air in 53f
evap air out 47f
cond air in 75f
cond air out 87f
box temp 51f
ambient 66f
pressures at 57/255

the subcooling is within range at 10f and the superheat is still really high. so i think i have to look at why the evaporator air in temp is always so high. even at times when the box temp was in the low 40's,, it was still running in the 50's. and this is a short run (like 12").

i built this wine cooler the same way that i built my backbar cooler,, and that is 7 foot long, 3 foot high, and 2 foot deep. it has 3 glass front doors, and the cooling unit is the same capacity. the backbar cooler does have a larger capacity coil,, and it is suspended in the middle of the box. but this cooler will freeze NA beer at times (it runs very cold).

ill check it again in the morning and see what i got.

Gary
26-12-2007, 05:51 PM
The numbers aren't making any sense. If the coil is frozen then the suction line should also be frozen and the temperature of the air leaving the coil should be at or below freezing. Instead, the leaving air is 47F and the suction line is 49F.

When you say the coil is frosted, exactly what part of the coil are you looking at?

Gary
26-12-2007, 06:33 PM
I'm thinking we need more pictures of the coil and TXV with the insulation and covers removed so we can see how it is all assembled. There is something very wrong here.

Do you have any specs on that TXV?

flyboy3b
26-12-2007, 07:16 PM
When you say the coil is frosted, exactly what part of the coil are you looking at?

i can see the center part of the coil through the fan while its running. in order to see the whole coil,, i have to remove the cover plate on the right side.

ill try to get some more pics tomorrow morning

flyboy3b
28-12-2007, 05:57 PM
I'm thinking we need more pictures of the coil and TXV with the insulation and covers removed so we can see how it is all assembled. There is something very wrong here.

Do you have any specs on that TXV?


here is the link for some new pics,,

http://wavespub.com/evapcoil.html

now dont laugh at my crappy cuts,,, i had to change this whole thing around after i installed it and its 2 1/2 inches thick. i plan on trimming it out after i get it running right.

here is the link to the txv,,

http://www.parker.com/cig/catalogs/CIC%202003/Section5Parker.pdf

the model # is C-A-SZ

i have to run some errands so ill finish this post in an hour or two

Gary
28-12-2007, 07:25 PM
Can you remove the sheet metal so that we can see the end of the coil?

The "A" says this is not a 1/4 ton valve, it is a 1 ton valve.

The "Z" means it is for a freezer, not a cooler.

The correct valve would be C-AA-SW

And here's the really bad news:

Being oversized and having a low temp (freezer) bulb charge, it should be running wide open and flooding the compressor. Instead the coil is not getting enough refrigerant. Either the TXV is severely restricted or the coil is severely restricted.

flyboy3b
28-12-2007, 08:12 PM
where did you get that information???

i read that pdf, and it looks like its a 1/4 to 1 ton txv. where did you look up the "z"?

flyboy3b
28-12-2007, 08:24 PM
nevermind,, i found it further down the page,, ill have to check my local suppliers to see if they have a txv thats applicable.

flyboy3b
28-12-2007, 09:01 PM
the new txv is coming in on monday,

thanks again gary

Gary
29-12-2007, 04:35 PM
When you get the new valve, do not adjust it unless the superheat is low. High superheat is to be expected until the return air temp is down to 40F or less.

flyboy3b
29-12-2007, 09:36 PM
gotcha,,,

depending on what time ups shows up,, it may end up being tuesday before i can install it. dec 31st is a busy day for us

tonyelian
31-12-2007, 08:25 PM
hi flyboy
it seems that you wont giveup thats good
is your box insulated well
did you fit a door switch to stop fan when its open
from your readings ithink that you need more capacity
i use to deal with that kind of boxes and my readings were
30 psi at the suction and275 dicharge using 404

joshman1
01-01-2008, 04:13 AM
I think your system is not sized up properly, your condensing unit is struggling mate, good luck.

flyboy3b
02-01-2008, 04:48 AM
hi flyboy
it seems that you wont giveup thats good
is your box insulated well
did you fit a door switch to stop fan when its open
from your readings ithink that you need more capacity
i use to deal with that kind of boxes and my readings were
30 psi at the suction and275 dicharge using 404


the doors could seal a little better,, but its ok,, and the box is very well insulated for such a small unit. i should be able to cool 4 boxes this size with this condensing unit. if you read back in the thread,, you will see that its very small. but i appreciate the ideas. 30 psig on the suction side sounds kinda low. my target temp is low 40's.

certainly getting the right txv in there will help. which , by the way,, never came in on monday. it should be in tomorrow and hopefully ill be able to install it right away.

thanks,
mike

tonyelian
02-01-2008, 11:35 PM
hi fly boy
sorry i did not see your site before my reply
so your comp e2145gk aspera is a lbp application&it gives you about2200btu at23 degree fah or -5 centigrade evaporation temp
so i think your txv is over sized&here what i am thinking you can fit a cap-tube 2.32meter&0.044 inche int diameter why?
you can remove the receiver so you can move your condensor back for more vent
you can fit your thermostat with diff direct to evaporator pipe letting the fan blows cold air
that thermostat will cycle the fan so your comp take a little break
fit another room thermostat
i hope that will help

flyboy3b
03-01-2008, 09:51 PM
so i think your txv is over sized&here what i am thinking you can fit a cap-tube 2.32meter&0.044 inche int diameter why?


thanks for the advice,, however,, i just got the new txv in and i installed it this morning. ill know more tomorrow morning when i take some more readings. until then,,,,, this is what i got.

ambient 68f
box (wine) 52f
liquid line at receiver 97f
suction line at txv bulb 30f (although this reading was bouncing around pretty good. from 22f to52f)
suction line at compressor 44f
evap air in 51f
evap air out 43f (and dropping)
cond air in 67f
cond air out 85f
pressures at 45 and 285 psig

subcooling 285 psig=113f-97f=16f
superheat 30f-10f (45psig)=20f

gary,, i forgot to get the picture of the evap coil,, ill try to get it in the morning. this cooler is still balancing out and i havent adjusted the txv. when i first fired it up,,, the suction pressure was at 65 psig. and it slowly dropped. the txv that i ordered was a C-A-SW, but the one they shipped was a C-A-RW. i couldnt find the "r" even listed on that pdf file,, but grainger assured me that it was the same application. (they didnt have the C-AA-SW)

anyhow,, until tomorrow am,
thanks again
mike

Gary
03-01-2008, 11:18 PM
Is it possible that some of the air is going around the coil instead of through the coil?

The "A" orifice in the TXV is rated 1 ton nominal, but will control down to 1/4 ton. You are currently running closer to 1/8 ton. The "AA" orifice is rated 1/2 ton nominal, but will control down to 1/8 ton. That's why the TXV is hunting (temps/pressures bouncing). Any air that bypasses the coil will reduce the tonnage and add greatly to this effect.

The TXV bulb should be mounted as close to the coil as possible, and should be heavily insulated (real insulation, not rags). Get a roll of closed cell foam insulation tape.

nike123
03-01-2008, 11:31 PM
Did you guys/girls noticed, that this troubleshooting thread is longest in RE archive. First next to this has "only" 77 posts!:D

Gary
04-01-2008, 12:14 AM
Hmmm... Is this a trouble shooting thread or a training thread. :confused:

flyboy3b
04-01-2008, 01:02 AM
Did you guys/girls noticed, that this troubleshooting thread is longest in RE archive. First next to this has "only" 77 posts!:D


its only that long because i am too dense to get it right the first time.



Is it possible that some of the air is going around the coil instead of through the coil?

sure,, its possible,, but how much air would have to bypass the coil before it became significant in such a small box. and even at that,, all the air going through the coil originated from the inside of the cooler, so eventually it will all get cold.

now that were done with all these holidays,, ill have some time to go back inside and tighten the whole unit up. remember,, when i originally installed this thing,, it was a 134a cap tube system. so i had some cutting to do to get it where it is now. i just dont want to get too much time in finishing it until im sure its running right.


Hmmm... Is this a trouble shooting thread or a training thread. :confused:

i think i feel an invoice coming :)

Gary
04-01-2008, 02:23 AM
its only that long because i am too dense to get it right the first time.

There's nothing like doing things over to drive the lesson home.



sure,, its possible,, but how much air would have to bypass the coil before it became significant in such a small box. and even at that,, all the air going through the coil originated from the inside of the cooler, so eventually it will all get cold.

The more air goes through the coil, the higher the heat transfer, the higher the efficiency, and the less likely the TXV is to hunt.


now that were done with all these holidays,, ill have some time to go back inside and tighten the whole unit up. remember,, when i originally installed this thing,, it was a 134a cap tube system. so i had some cutting to do to get it where it is now. i just dont want to get too much time in finishing it until im sure its running right.

Insulation, especially on the TXV bulb, is part of getting it running right.

flyboy3b
04-01-2008, 05:46 PM
and yet once again,,, more readings
this morning 6am,,,
ambient 76f
box 47f
suction at bulb 40f
liquid at receiver 101f
cond air in 73f
cond air out 84f
evap air in 52f
evap air out 45f
pressures at 55/290 psig
subcooling of 14f and superheat of 21f

i pulled the top apart and added some insulation and generally tightened things up and then i let it sit for a couple of hours. here are the readings i just took,,,

suction line at bulb 30f
liquid line at receiver 96f
cond air in 67f
cond air out 88f
evap air in 45f
evap air out 38f
pressures at 45/285 psig
subcooling of 16f and superheat of 20f
the suction line was starting to frost back to the compressor and the temperature of the suction line at the compressor was 50f.

here are some variables to take into consideration,,, when i take the evaporator air in temp,, it can vary by how far i push the probe in. and being thats its a wire probe (not solid) i cant be sure that its not touching something inside and affecting the temperature. the same thing is true with the condenser air in temp. moving the probe a few inches will make a difference of +-12f. so i try to take these temps the same way each time to keep them relative to each other. the other thing is,, i think thermostat may be shutting off too soon,, so i adjusted it down,, and moved the probe further into the return air duct. now it should run longer and give me some more stable readings.

i did take some more pictures but it will be later today before i can post them. oh,, and i still need to tape the txv bulb.

flyboy3b
04-01-2008, 08:35 PM
heres the link for the new pics,, you cant really see much and remember,, when its back together,, the coil is tight against the left side of the box,, so no air is getting by.
http://wavespub.com/evapcoil1.html

for what its worth,, it seems to be doing much better today.

Gary
04-01-2008, 08:43 PM
I think we can move the thermostat sensor inside the box, mounting it at the entrance to the return air duct... and we can take the evap air in readings there, also.

The numbers are looking much better with the new TXV.

There is good airflow through the evap... the weakest link seems to be the coil itself.

Gary
04-01-2008, 09:02 PM
Is the TXV still hunting?

flyboy3b
04-01-2008, 09:39 PM
i havent looked at it since this morning,, but it seemed to be stabilizing. there was a steady (light) frost on the suction line and the evap air out was dropping nicely. i will hook up my datalogger and see just how often the thermostat is shutting it down.

Gary
04-01-2008, 10:43 PM
Looking at the pic, that appears to be an upside down condenser coil... lol

Actually, its a good thing that you have it upside down or the subcooling loop would trap oil.

tonyelian
05-01-2008, 08:06 AM
hi fly boy
it look like a condensor not evap you have fin spacing problem freezing up anyway waiting for your latest readings
best regards for you&gary

flyboy3b
05-01-2008, 04:35 PM
actually,, its a radiator from a 65 rambler classic 550

flyboy3b
06-01-2008, 05:27 PM
its warm(45f) and rainy here in wisconsin and here are the latest readings...

ambient 80f
box 41f
evap air in (from the intake) 38f
evap air out 41f
cond air in 74f
cond air out 91f
suction line at bulb 30f
liquid line at receiver 105f
pressures at 45 and 295 psig

this leaves me with a superheat of 19f and subcooling of 10f. the txv was fairly stable but the pressure seems low to me so i turned the txv 1 full turn ccw. also,, the coil was starting to frost up. i shut it down for about 15 mins and restarted. after about 1/2 hour the pressures were at 50 and 300 psig and the superheat had dropped to 17f.

after restarting,, the txv was hunting a little (suction line temps between 30f and 35f over a cycle of about 30 seconds, but that was starting to smooth out when i left it. i think im getting close here and i am pretty certain there are no leaks in the system.

of course,, im waiting for gary's intuitive insight and profoundly sage advice before i lock this cooler down.

thanks,
mike

thermo prince
06-01-2008, 06:04 PM
Hi Gary, before Nike 123 posted his interesting observation, I was just thinking to myself, the tremendous job you had done in guiding FlyBoy through this project thus far.

However, the downside ... I fear it will impact your book sales !! :eek:

Why? because you have (kindly) divulged most of your knacks and techniques over the course of this 77+ post thread. :D :D . Many of the newbies may have all they need ( if they are sharp on the uptake!)

kind regards :)
T-P

flyboy3b
06-01-2008, 06:44 PM
Hi Gary, before Nike 123 posted his interesting observation, I was just thinking to myself, the tremendous job you had done in guiding FlyBoy through this project thus far.

However, the downside ... I fear it will impact your book sales !! :eek:


and thats exactly the reason why i bought 3 of them.




Why? because you have (kindly) divulged most of your knacks and techniques over the course of this 77+ post thread. :D :D . Many of the newbies may have all they need ( if they are sharp on the uptake!)

kind regards :)
T-P

i cant speak for everyone,, but i, myself,, find that the smarter i get,, the dumber i feel. i already own a few troubleshooting manuals. it seems that everyone has a slightly different method. by learning these different methods i hope to consolidate these methods into something that works for me. i would reccommend to anyone who is new to the trades like myself (and possibly some of the veterans who never bothered to learn the theory) to read as much literature and training as possible to gain a better understanding of the whole process. there are so many variables to consider and so many times we see techs who merely swap out parts rather than diagnose.

again,, many thanks to you gary for your time and patience,
mike

thermo prince
06-01-2008, 06:56 PM
It's all good - a very pleasant and polite thread which made rivetting reading! Better than primetime TV here even ! :D

Sorry to jump into your posts if it's not entirely concluded yet but it appears to be getting close now.

Good luck with rest of it FlyBoy.
And Gary I must review your material soon to see if and which parts may be helpful in Transport HVACR training programmes. Of course the fundamentals are universal.
Can you tell from sales records if any Transport people in USA have purchased yr books previously?

best regards
T-P

flyboy3b
06-01-2008, 07:39 PM
Sorry to jump into your posts if it's not entirely concluded yet but it appears to be getting close now.

youre not intruding at all. isnt that what this forum is all about?

Gary
06-01-2008, 07:39 PM
evap air in (from the intake) 38f


Judging from the previous evap delta-T's, the evap air in (at the coil) would be about 48F, so we can estimate that the return duct is gaining at least 10F (48 - 38 = 10F gain). That's a HUGE gain.

You really need to do something about the return air duct. It needs to be leak-free and very heavily insulated. The temp at each end of that duct should be nearly identical.

Possibly the heat gain is coming from the evaporator compartment itself, so the compartment should be leak-free and heavily insulated also.

A lot of heat is getting in somewhere.

flyboy3b
06-01-2008, 07:51 PM
You really need to do something about the return air duct. It needs to be leak-free and very heavily insulated. The temp at each end of that duct should be nearly identical.

i was thinking it might be better to just eliminate the return duct and enlarge the evaporator chamber. (basically just hang the coil in the cooler space,,, so to speak). that would eliminate any chance of other air leaking in. give me a couple days to think about some other options,, and to let the cooler settle down,, and ill repost the current results.
one thing i notice,, when im taking the evap air out temp,,, is how fast that temperature rises when i open the door. there should be no negative or positive pressure difference inside the box, but it sure seems to draw outside air in fast when i open the door.

anyhow,, till next time,
thanks,
mike

Gary
07-01-2008, 12:51 AM
Hi Gary, before Nike 123 posted his interesting observation, I was just thinking to myself, the tremendous job you had done in guiding FlyBoy through this project thus far.

However, the downside ... I fear it will impact your book sales !! :eek:

Why? because you have (kindly) divulged most of your knacks and techniques over the course of this 77+ post thread. :D :D . Many of the newbies may have all they need ( if they are sharp on the uptake!)

kind regards :)
T-P

I would like to think that this thread has been helpful to many people, but it is in fact just a small taste of what's in my books.

nike123
07-01-2008, 04:12 PM
Just to point out, my previous observation has nothing to do with content of this thread. It is just observation that this is longest thread of this forum.

knight rider
07-01-2008, 09:06 PM
IF I COULD I WOULD VOTE FOR GRAY USA PRESIDENT

and i am gone buy a set off his books ,

Gary
07-01-2008, 09:28 PM
IF I COULD I WOULD VOTE FOR GRAY USA PRESIDENT


Hmmm... on day one I would issue a presidential pardon to all non-violent drug offenders.

On day two I would pardon all tax evaders.

On day three I would be assassinated... LOL

thermo prince
08-01-2008, 08:38 AM
Hi again Gary, Knight rider .... a good man to run no doubt but bad address. :rolleyes:
FLORIDA - hmmmm was'nt that where all the fun occurred last time ? :D
Florida, President-elects, Governors, re-counts, hanging chads :D:D
If you wanna run, could you not temporarily move 'next door' to like Tennessee or the Carolinas for a while? LOL !:)

Hi Nike 123 - sorry I did not mean to imply you made any observation regarding content in a positive/negative light whatsoever - I simply referred to your observation of the post count( at 77) thus far in making my follow -on comment ! :):)

best regards
T-P

flyboy3b
08-01-2008, 04:32 PM
IF I COULD I WOULD VOTE FOR GRAY USA PRESIDENT

and i am gone buy a set off his books ,

gary, can we legalize homebuilt distilleries?

Gary
09-01-2008, 03:05 AM
gary, can we legalize homebuilt distilleries?

Yep... but if you poison anyone (other than yourself) you're in big trouble.

flyboy3b
09-01-2008, 05:52 AM
Yep... but if you poison anyone (other than yourself) you're in big trouble.

you sound like one of those non-believers. i could no more poison you with homemade rum,, than you could poison me with ditch weed.

one of the common misconceptions with home brew is poisoning. now,, there were moonshiners back in prohibition that would add things to "thin" out their brew,,, and the government makes us add poison to make rubbing alcohol undrinkable (denatured). but distilling is a purifying process where bad things are removed. and there arent alot of bad things to begin with,, mostly stuff that tastes funny, and you would have to drink a whole lot of those bad things to even get sick (and youd probably get sick from the alcohol first).

george washington was a big proponent of home distilling and he thought everyone should have one in their yard.

do i sound fanatical??

Gary
09-01-2008, 10:44 PM
What is "ditch weed"?

flyboy3b
09-01-2008, 10:49 PM
Hmmm... on day one I would issue a presidential pardon to all non-violent drug offenders.



its street language for homegrown pot

Gary
11-01-2008, 04:35 PM
its street language for homegrown pot

I never use the stuff... and I rarely use alcohol. But if others want to use all of the above, I have no right to stop them. I have a simple philosophy: If you want to smack yourself in the head... it's your head.

If you want to smack someone else's head, that's a different story. The legitimate basis of government is collective self defense.

TRASH101
11-01-2008, 05:15 PM
A flawed philosophy I`m afraid

someone may get smacked in the head and then blame you.

someone might pretend to get smacked in the head and blame you.

you might try and smack yourself in the head miss and hit the person beside you.:D

But in essence a really sound philosophy:)

flyboy3b
11-01-2008, 06:46 PM
I have a simple philosophy: If you want to smack yourself in the head... it's your head.


i am enjoying my new hobby of home distillation and it pleases me no end that i can make something that tastes better and is cleaner than what i can buy in the store. everything in moderation i guess. anyhow,, i have a different forum for home distillation so ill get back to things at hand...

ambient 75f
box 44f
cond air in 75f
cond air out 91f
evap air in 53
evap air out 41f
suction at bulb 32f
suction at compressor 53f
liquid at receiver 104f
pressures at 60/295 psig

this leaves me with 11f superheat and 12f subcooling. the txv was wandering between 29f and 32f bulb temperature and seemed pretty normal. the unit may be a bit overcharged.

at this point, i think, once i get the evaporator air in temperature down about 6 or 7 degrees i will need to increase the superheat a couple of turns which should lower the pressure a tad and bring the evaporator air out temp down 1 or 2 degrees. otherwise,, we are in the ballpark.

gary,, once again,, i thank you for your time and patience. and of course to everyone else who shared thier ideas. i have started to read the manuals i got from you and im waiting for the next time i can try out the TECH system (which may be sooner than later, i had my manitowoc ice machine apart this morning and it was flashing an error code that the harvest cycle had exceeded 3 1/2 minutes 3 times) i reset the machine and watched it through 3 cycles with no problem).

itll be a bit before i can tear that wine cooler apart to redo the air intake,, but ill keep you posted as to the results.

to summarize,,, (and please correct me if im wrong)...

the original question was "how do i know when i have the charge right in a medium temp home built system"

the answer is,,,

add refrigerant until the subcooling reaches around 15f.
keep the superheat between 20f and 30f
keep the delta t for the condenser to less than 30f
keep the delta t for the evaporator less than 20f
assuming that everything else seems normal, the charge is correct.

Gary
12-01-2008, 01:06 AM
A flawed philosophy I`m afraid

someone may get smacked in the head and then blame you.

someone might pretend to get smacked in the head and blame you.

you might try and smack yourself in the head miss and hit the person beside you.:D

But in essence a really sound philosophy:)

Hmmm... perjury should be illegal... perjury should be illegal... accidents happen, you pay for the damages you cause.

Gary
12-01-2008, 01:45 AM
The charge is enough to do the job, but you might add just a little more refrigerant to bring the subcooling up to 15F.

The superheat looks just right... leave it alone.

The condenser TD is a little high, but I stopped believing the cond air in temp a long time ago and we know the condenser is not in an ideal spot.

The evaporator TD is high, but that's because it doesn't have much surface area. It's not like a real evaporator... lol

The major problem at this point is the return air.

Everything else is looking pretty good... considering.

flyboy3b
13-01-2008, 04:08 PM
okey dokey,, here we go again. yesterday the cooler had warmed up. i pulled it apart and hooked up my gauges. the low pressure was way high. like 90 psig and the high side was normal at around 300 psig. i adjusted the txv all the way down and the pressure dropped and i could hear the refrigerant when i opened it back up again.

so this morning i rechecked it, i did a leak check on it, pumped it down to rule out noncondensibles and i refilled it. there was no change so i closed off the receiver valve and it pumped down to 10 inches of vacuum which it held for at least 20 mins.

im thinking its the txv, but its brand new. any thought on this matter would be appreciated.
thanks,
mike

flyboy3b
13-01-2008, 04:40 PM
and as an after thought. what condition might cause a txv to fail? its like the spring is broken or the valve is stuck.

Gary
13-01-2008, 06:06 PM
okey dokey,, here we go again. yesterday the cooler had warmed up. i pulled it apart and hooked up my gauges. the low pressure was way high. like 90 psig and the high side was normal at around 300 psig.

And you didn't take readings to find out what was wrong? :confused:

Gary
13-01-2008, 06:08 PM
and as an after thought. what condition might cause a txv to fail? its like the spring is broken or the valve is stuck.

There is nothing wrong with the TXV and it was adjusted just right. At that point it should have been put under lock and key and throw away the key so you couldn't mess with it... ever again.

Once a TXV is adjusted it should never need to be adjusted again. There is a long list of things that can go wrong with a system. The TXV is never at the top of the list, it is at the very bottom of the list. Eliminate all other possible problems before suspecting or adjusting the TXV.

Gary
13-01-2008, 06:37 PM
there was no change so i closed off the receiver valve and it pumped down to 10 inches of vacuum which it held for at least 20 mins.



The compressor should be able to pump at least 15 inches of vacuum.

Remember back when I said the suction line should come out of the coil, down then up (oil trap), to the top of the coil and back down (reverse trap), then to the compressor?

The coil will gather liquid during the off cycle. If the suction line goes straight down to the compressor then gravity can fill the compressor crankcase with liquid. The compressor then starts, washes out the oil and tries to pump liquid, which can break the compressor valves. The reverse trap prevents this. You did install the traps, right?

flyboy3b
13-01-2008, 07:01 PM
i didnt see much point in taking all the temps. the box was warm,, the evap air in and out was warm. the air going in and out of the condenser was warm the liquid line was warmer,, but not hot. i have no idea of what the superheat was,, but i with the pressure being so high,, i didnt see much point in checking. i have three trouble shooting manuals,, including your own and i cant find anything that diagnoses a box with high high side pressure, very high low side pressure and everything is warm.

flyboy3b
13-01-2008, 07:04 PM
The compressor should be able to pump at least 15 inches of vacuum.

Remember back when I said the suction line should come out of the coil,


maybe my guage is off by 5 lbs,, i dont know,, but would it make that much difference (cold one day and warm the next)?

and i did put that loop in the suction line

Gary
13-01-2008, 07:16 PM
The high side pressure is elevated because you have the condenser boxed in and trapped up against a wall. The hot air is recirculating.

flyboy3b
13-01-2008, 07:19 PM
maybe you dont understand,,,

everything is warm

something is wrong ,,, the cooler has been in the same place since i installed it and it was cooling before,, and now its not.

Gary
13-01-2008, 07:27 PM
Take readings.

flyboy3b
13-01-2008, 07:43 PM
the soonest i can get back in there now will be this afternoon,, if its not busy,, otherwise ill be working on it tomorrow

Gary
13-01-2008, 07:54 PM
i have three trouble shooting manuals, including your own and i cant find anything that diagnoses a box with high high side pressure, very high low side pressure and everything is warm.

Elevated high side pressure tells you absolutely nothing. Elevated low side pressure tells you absolutely nothing. Everything is warm tells you absolutely nothing.

The TECH Method procedure is sequential. Do not pass go, do not jump to the pressures, do not jump to the TXV, do not jump to non-condensables, do not jump at all.

Follow the procedure step by step.

flyboy3b
13-01-2008, 09:02 PM
Do not pass go, do not jump to the pressures, do not jump to the TXV, do not jump to non-condensables, do not jump at all.

Follow the procedure step by step.


i didnt jump to anything. i felt every line, i felt the txv, i felt the temp in the inside of the cooler. then i thought about it last night,, and did some reading.

this morning, i checked it again. everything was warm. the low side pressure was 90 psig. so i tapped on the txv,, thinking it might have been stuck. the high side pressure seemed normal and the liquid line was warm (i felt the same as any other time ive checked it). so i tried a valve test by closing the receiver valve. the results from that seemed within range. now,, i asked myself,, i said "self",,, " what else could cause the low side pressure to be so high in just one day" and myself replied,,, "it must be the txv". so i adjusted it down one full turn at a time,, and the pressure didnt change until it was almost closed. one more half turn and the txv closed.

i just took these readings with the txv back in the middle,,,

suction line at bulb 68f
suction line at compressor 68f
liquid line at receiver 96f
cond air in 74f
cond air out 90f
evap air in 69f
evap air out 68f
ambient 77f
bos 77f
pressures at 85 and 270 psig
14f subcooling
28f superheat

tonyelian
13-01-2008, 10:09 PM
hi flyboy
first of all you have to check your comp
i have adjust the txv all the way down so i think your low side should show a lowest reading
in my point of view all your readings from the first post the low &high side are high its winter time & what would you do in summer time you should see these reading in the most hottest days
in my opinion your major problem came from 3 things
1-expansion device
2-evaporator fan speed
3-insulation your box-air leakeage-design of air circulation in your box
your compressor is a lbp application &it suffer to much so if it still alive try to switch to a cap. tube&you will see the difference your project needs a little change &worth to do it after 180 posts.

flyboy3b
13-01-2008, 10:27 PM
what would you do in summer time you should see these reading in the most hottest days
in my opinion your major problem came from 3 things
1-expansion device
2-evaporator fan speed
3-insulation your box-air leakeage-design of air circulation in your box
your compressor is a lbp application &it suffer to much so if it still alive try to switch to a cap. tube&you will see the difference your project needs a little change &worth to do it after 180 posts.

i agree,, i may have to change the configuration in the summer. i can always go to a remote condensing unit, but i will wait and see how it does. i started this cooler out with a cap tube and a different compressor using 134a. it didnt have enough capacity for the space. but perhaps this compressor might be better suited for the cap tube.

it should run with what is has in it,, so i will try that first,, but i thank you for your advice.
mike

Gary
14-01-2008, 12:40 AM
Is the return duct disconnected? It acts like it is sucking in nothing but room air.

Gary
14-01-2008, 12:44 AM
i asked myself,, i said "self",,, " what else could cause the low side pressure to be so high in just one day" and myself replied,,, "it must be the txv". so i adjusted it down one full turn at a time,, and the pressure didnt change until it was almost closed. one more half turn and the txv closed.


The TXV doesn't control the low side pressure, it controls the superheat. The low side pressure is about temperatures.

flyboy3b
14-01-2008, 01:11 AM
The TXV doesn't control the low side pressure, it controls the superheat. The low side pressure is about temperatures.

i understand that it controls the superheat, but how come when i adjust the txv,, the low side pressure changes?

and no,, the air intake is the same. as far as i know,, everything is the same. i really think this is a mechanical failure.

Gary
14-01-2008, 01:58 AM
If the TXV were overfeeding, the result would be low superheat. The superheat is not low.

flyboy3b
14-01-2008, 02:06 AM
but why is the pressure so high then? all of a sudden like.

flyboy3b
14-01-2008, 02:20 AM
if there were access valves on either side of the txv,, theoretically the pressures should about 50 and 300 for this system (thereabouts). it seems to me that the txv is not doing its job by regulating the pressure correctly?

Gary
14-01-2008, 02:23 AM
Why is the evap delta-T only 1F? I suspect the actual evap air in temp is much higher than 69F. Could air be leaking in around the sides of the evaporator chamber?

Gary
14-01-2008, 02:27 AM
if there were access valves on either side of the txv,, theoretically the pressures should about 50 and 300 for this system (thereabouts). it seems to me that the txv is not doing its job by regulating the pressure correctly?

There are no "should be" pressures. The pressures depend upon the temperature and volume of airflow entering the coils, as well as the pumping efficiency of the compressor... and the TXV's job is to regulate the superheat, not the pressure.

flyboy3b
14-01-2008, 02:44 AM
Why is the evap delta-T only 1F? I suspect the actual evap air in temp is much higher than 69F. Could air be leaking in around the sides of the evaporator chamber?

the delta-t is low because there is NO cold air,,, its all the same temp. the txv is barely cold. ive looked at that chamber a bunch of times now. besides,, it was fine a day ago. its been fine since i replaced the txv.

i guess i learned that there needs to be a pressure drop in order for there to be cooling,, and the txv is where that pressure drop happens. so if the pressure before the txv is right,, then the txv isnt doing its job in dropping the pressure sufficiently. if i were to adjust the txv to almost closed,, the pressure would be fine but there would be no refrigerant flow.

am i wrong here in this understanding?

Gary
14-01-2008, 03:02 AM
On the high side the pressure needs to correspond to a temperature that is higher than the temperature of the air entering the condenser, so that the heat will transfer from the refrigerant to the air.

On the low side the pressure needs to correspond to a temperature that is lower than the temperature of the air entering the evaporator, so that the heat will transfer from the air to the refrigerant.

You are confusing yourself with pressures. Refrigeration is about temperatures and heat transfer. It is not about pressures. The only reason you put gauges on the system is to determine the saturation temperatures.

The evaporating temperature aka saturated suction temperature (SST) is about 40F. The air entering the evap is 69F. Heat is transferred between the air and the refrigerant, therefore the temperature of the leaving air should be much lower... OR... the temperature of the air entering the evaporator is in fact much higher than 69F.

flyboy3b
14-01-2008, 03:29 AM
The only reason you put gauges on the system is to determine the saturation temperatures.


well,, the day before yesterday,, that gauge read 50 psig,,and the temperature was 42 and now it isnt,, and the box is the same.

Gary
14-01-2008, 03:48 AM
The day before yesterday, the difference between the leaving air temp and the SST was about 28F (approach). Now the approach is about 27F. So the heat transfer is about the same. But the day before yesterday the air in temp was 53F. Now it is 69F... and if the heat transfer is the same, then the air in temp must be much higher than 69F. Something changed. Whatever has been heating the return air got worse.

Gary
14-01-2008, 03:54 AM
The day before yesterday the delta-T was 12F. Today it is 1F. If the approach is the same then the actual delta-T should be about the same. If the delta-T is the same, then the actual air in temp is about 80F, not 69F.

flyboy3b
14-01-2008, 04:06 AM
ill look at more in the morning,, see if i can see any other cause. i really dont see anything different at this point.

and thanks again for your time,
mike

Gary
14-01-2008, 05:54 PM
Describe the return duct for us. Is it metal?... plastic?... insulated?

At the very least it should be insulated flexduct, such as used for A/C systems.

The evaporator chamber itself should also be sealed and insulated.

Notice the construction of the box. It is double wall with insulation in between. Insulation is important.

Gary
14-01-2008, 06:05 PM
Another thing I noticed while looking at the pictures: The evaporator coil is right up against the fan. There should be a space in between them to draw air evenly through the coil.

flyboy3b
14-01-2008, 08:14 PM
Describe the return duct for us. Is it metal?... plastic?... insulated?

At the very least it should be insulated flexduct, such as used for A/C systems.

The evaporator chamber itself should also be sealed and insulated.

Notice the construction of the box. It is double wall with insulation in between. Insulation is important.

the duct is basically 2 - 6" galvanized elbows going from the side of the box to the bottom of the evap chamber and it is insulated.

the box is 3/4" birch plywood with 1" foil covered foam insulation sandwiched in between. the doors are double glazed with a 1/2" space between.

the evap chamber is 3/4" plywood with 1 1/2 " stryofoam on the top and right side (the left side borders the cooler) and 1" foil covered foam in the back. the bottom is just plywood.

i built my back bar cooler and its the same construction and much larger and the condensing unit is the same size as the wine cooler. the back bar cooler has been working fine for almost 4 years.


Another thing I noticed while looking at the pictures: The evaporator coil is right up against the fan. There should be a space in between them to draw air evenly through the coil.

there is a couple of inches between the fan and the coil.

anyhow,, i checked it this morning,, and it has started cooling again and im confused. i understand that the pressures are relative to the temperatures of the ambient air, air flow, and box temperatures. but,,,,

the ambient temps have been basically the same this whole time.

even when the box was warm, the txv would still frost up.

even though the superheat was really high the txv would still frost up.

through this whole thing,, the low side pressure had never been this high.

anyhow,, here are the new readings,,,

ambient 76f
box 52f
suction line at bulb 42f
suction at compressor 51f
liquid line at receiver 97f
cond air in 77f... out 86f
evap air in 53f... out 44f
pressures at 60 and 270 psig
superheat 19f
subcooling 16f

and yes,, i agree that there are inefficiencies in this sytem, but that doesnt explain the huge difference over the last couple of days.

flyboy3b
14-01-2008, 08:16 PM
the box is 3/4" birch plywood with 1" foil covered foam insulation sandwiched in between. the doors are double glazed with a 1/2" space between.



make that double 3/4" plywood

Gary
14-01-2008, 11:09 PM
the duct is basically 2 - 6" galvanized elbows going from the side of the box to the bottom of the evap chamber and it is insulated.

I would strongly recommend the insulated flexduct.


the evap chamber is 3/4" plywood with 1 1/2 " styrofoam on the top and right side (the left side borders the cooler) and 1" foil covered foam in the back. the bottom is just plywood.

The bottom and front should be insulated as well. Hot air rises up from the condensing unit.


anyhow,, i checked it this morning,, and it has started cooling again and im confused. i understand that the pressures are relative to the temperatures of the ambient air, air flow, and box temperatures. but,,,,

the ambient temps have been basically the same this whole time.

even when the box was warm, the txv would still frost up.

even though the superheat was really high the txv would still frost up.

through this whole thing,, the low side pressure had never been this high.

What I was seeing was essentially the same heat load being pumped by the condensing unit, but the evaporator load was much greater. In other words, the system was working about the same, but more heat load was entering, specifically in the return air. That return duct seems to be the achilles heel of this system.


anyhow,, here are the new readings,,,

ambient 76f
box 52f
suction line at bulb 42f
suction at compressor 51f
liquid line at receiver 97f
cond air in 77f... out 86f
evap air in 53f... out 44f
pressures at 60 and 270 psig
superheat 19f
subcooling 16f


You might want to open the TXV 1/2 turn. I would like to see the superheat back down around 12F.

flyboy3b
14-01-2008, 11:19 PM
You might want to open the TXV 1/2 turn. I would like to see the superheat back down around 12F.

im not sure how long it had been cooling when i took those measurements,, ill check it again in a little while, now that its had a chance to cool down inside the box.

and yes,, there are adjustments i can make to tweak this cooler,, and i will. but im still miffed as to why the sudden change. as i said before,, the txv was warm. before that,, despite all the inefficiencies,, the txv would always frost up,, and the pressure (or temp) at the txv was never that high.

Gary
14-01-2008, 11:49 PM
The increased heat load warms the refrigerant, increasing its pressure/temperature. The warm refrigerant (40F) is not going to frost anything.

We know the return has been a problem all along. Why did the return suddenly decide to leak more heat than previously? I don't know.

flyboy3b
14-01-2008, 11:56 PM
The increased heat load warms the refrigerant, increasing its pressure/temperature. The warm refrigerant (40F) is not going to frost anything.



again,, pardon my stupidity,, but right at the txv,, the heat load doesnt exist yet. does it?

Gary
15-01-2008, 12:01 AM
Actually, the refrigerant going through the TXV is warm liquid which quickly flashes off to bring its temperature down to the saturation temperature (40F). So at that point it is not yet down to 40F.

flyboy3b
15-01-2008, 12:25 AM
but that liquid was no warmer yesterday,, than it was a week ago. wouldnt the liquid line have to be hotter to increase the pressure on the low side of the txv to where it was yesterday??

flyboy3b
15-01-2008, 02:42 AM
heres the latest,,

suction line at bulb 58f
liquid line at receiver 93f
evap in 47f
evap out 39f
cond in 71f
cond out 85f
ambient 74f
pressures at 60 and 265 psig
superheat at 35f
subcooling at 17f
it seems like were losing ground here,, but ill check in the morning

flyboy3b
15-01-2008, 03:38 AM
actually,, thinking about it,, im not sure how long it had been running for when i took those temps. it may have just started before i looked at it.

Gary
15-01-2008, 05:41 AM
but that liquid was no warmer yesterday,, than it was a week ago. wouldnt the liquid line have to be hotter to increase the pressure on the low side of the txv to where it was yesterday??

The low side pressure/temperature is regulated by the temperature and volume of the air passing through the evaporator.

The low side temperature (and thus pressure) was warmer yesterday because the airflow entering the evaporator was warmer.

The warm liquid leaving the TXV must drop in temperature to match the low side temperature. It is not the cause of the low side temperature/pressure. The heat from the air is.

Gary
15-01-2008, 05:54 AM
heres the latest,,

suction line at bulb 58f
liquid line at receiver 93f
evap in 47f
evap out 39f
cond in 71f
cond out 85f
ambient 74f
pressures at 60 and 265 psig
superheat at 35f
subcooling at 17f
it seems like were losing ground here,, but ill check in the morning

I don't think we're losing ground at all. The superheat is higher, but we know that the TXV orifice is oversized which will cause it to hunt, especially when it first starts.

We can open it another 1/2 turn and see how that does.

Gary
15-01-2008, 06:46 PM
I would strongly recommend the insulated flexduct.


If you want to stick with the metal duct for the rigidity, you might seal it with duct tape and then insulate it with sheet Armaflex (closed cell foam).

An alternative would be several layers of Armaflex foam tape. Start at one end of the duct, spiral the tape around the duct, overlapping about halfway across the previous spiral, to the other end of the duct. Run the system for awhile. If the surface of the tape is cool to the touch, add another layer.

flyboy3b
15-01-2008, 08:32 PM
If you want to stick with the metal duct for the rigidity, you might seal it with duct tape and then insulate it with sheet Armaflex (closed cell foam).



as is said before,, once i know the system is gonna be ok,, i will redo a few parts,, including teh evaporator chamber. i figure to eliminate that duct and just suspend the coil and draw air through it.

here are the latest readings,,,
ambient 74f
box 41f
suction line at bulb 34f
liquid line at bulb 97f
evap air in 45f out 36f
cond air in 77f out 89f
superheat 18f
subcooling 15f
pressures at 55/275 psig

lol,, this thing is bouncing around so much. if i can get a few steady readings,, im close,, i think

Gary
15-01-2008, 11:10 PM
I would give it a layer of foam tape anyway, even if it's just temporary.

Gary
15-01-2008, 11:16 PM
In your pictures, it looks like the duct "insulation" is a towel. I'm wondering if it got damp enough the other day to nullify it's insulating effect, then dried out and started working again.

flyboy3b
16-01-2008, 03:44 AM
In your pictures, it looks like the duct "insulation" is a towel. I'm wondering if it got damp enough the other day to nullify it's insulating effect, then dried out and started working again.

there is insulation under that,, and no,, ive been trying to think of what happened when it warmed up,, but thats not it,,, everything was dry.

in my opinion,, in my vast experience,, i think the txv stuck open. it still provided enough resistance to keep the pressure under 100 psi, but not enough of a drop in pressure to provide cooling. all of the other factors seemed the same as any other day. it certainly got as warm,, if not warmer,, in the time we have been discussing that cooler. i can see no other significant differences that would cause that drastic of a change.

Gary
16-01-2008, 04:45 PM
there is insulation under that,, and no,, ive been trying to think of what happened when it warmed up,, but thats not it,,, everything was dry.

in my opinion,, in my vast experience,, i think the txv stuck open. it still provided enough resistance to keep the pressure under 100 psi, but not enough of a drop in pressure to provide cooling. all of the other factors seemed the same as any other day. it certainly got as warm,, if not warmer,, in the time we have been discussing that cooler. i can see no other significant differences that would cause that drastic of a change.

I have no idea what heated the return air, but that is what caused the problem.

A stuck open TXV would have given us very low superheat and flooded the compressor. That didn't happen.

flyboy3b
16-01-2008, 05:21 PM
this mornings readings are,,,

ambient 77f
box 43f
suction line at bulb 41f
liquid line at receiver 99f
cond air in 74f / out 90f
evap air in 52f / 41f
pressures at 60/275 psig
superheat 18f
subcooling 13f

well,, maybe itll happen again

Gary
16-01-2008, 09:58 PM
this mornings readings are,,,

ambient 77f
box 43f
suction line at bulb 41f
liquid line at receiver 99f
cond air in 74f / out 90f
evap air in 52f / 41f
pressures at 60/275 psig
superheat 18f
subcooling 13f

well,, maybe itll happen again

Actually, the numbers are looking a little better. Try another half turn out on the TXV.

Gary
18-01-2008, 04:42 PM
How is our wine cooler doing? Have we gotten the superheat down to 12F yet?

nike123
18-01-2008, 04:48 PM
Maybe his vine is properly cooled now and he enjoy his vine finally.:D
That is what I will do if that is my case.:D

flyboy3b
18-01-2008, 06:28 PM
How is our wine cooler doing? Have we gotten the superheat down to 12F yet?

sorry,, i just got busy. itll be a couple days before i can get back in there. but just from casual observations,, it seems to be doing ok.

knight rider
18-01-2008, 07:21 PM
hi flyboy , if its doing ok , PLEASE DONT TOUCH !!!

flyboy3b
18-01-2008, 08:15 PM
hi flyboy , if its doing ok , PLEASE DONT TOUCH !!!


lol,, advice well taken,, thanks

thermo prince
19-01-2008, 03:31 AM
Whoaaaaa ? U mean this saga may come to an end ?

NO ! pls keep on toying with it , Flyboy !! :D :D

You've now got the " tamperitis" bug of fiddling with tx valves.

All us avid readers around the globe need our daily fix of this thread :)

Try and screw it up again so we can keep this project going .... if Gary was charging u for advice, it would have to go on record as the most expensive wine cooler in history!!!!

yuk yuk :D :D

regards
T-P

flyboy3b
21-01-2008, 06:59 PM
hi honey,, im hoooome.
sorry guys,, ive been a little under the weather. anyhow,, these are the readings i took this morning,,,

ambient 74f
box 38f
cond air in 67f,, out 81f
evap air in 46f,, out 38f
liquid line at receiver 91f
suction line at bulb 40f
pressures at 50 and 255 psig
superheat 25f
subcooling 14f.

i opened the txv 2 turns and ill let it settle out and take the readings again in an hour or two.



Try and screw it up again so we can keep this project going ....

theres plenty of time for that T-P,,, i believe its a god given right for a man to make a fool of himself,, and i excersize that right often.

Gary
21-01-2008, 08:03 PM
I assume the suction line is insulated between the coil and the bulb... and the bulb heavily insulated?

flyboy3b
21-01-2008, 08:20 PM
i opened the txv 2 turns

let me rephrase that,, i opened the txv 2 quarter turns = 1/2 turn.

yes,, the valve and line are insulated

Gary
21-01-2008, 09:18 PM
ambient 74f
box 38f
cond air in 67f,, out 81f
evap air in 46f,, out 38f
liquid line at receiver 91f
suction line at bulb 40f
pressures at 50 and 255 psig
superheat 25f
subcooling 14f.


Our superheat seems unwilling to cooperate. Is the TXV still hunting?

Gary
21-01-2008, 09:27 PM
I wonder if the high side gauge is off a few psi, leading us to believe that the subcooling is higher than it actually is?

Connect the high side gauge to your refrigerant tank. The pressure should agree with the temperature of the tank.

flyboy3b
21-01-2008, 10:10 PM
I wonder if the high side gauge is off a few psi, leading us to believe that the subcooling is higher than it actually is?

Connect the high side gauge to your refrigerant tank. The pressure should agree with the temperature of the tank.

to be honest,, taking the suction line reading seems very fickle. sometimes i have to take the reading several times before i get a reading that seems right (i take the lowest reading).

no,, the suction line temp is very stable (within a couple degrees). here are the latest readings,,,

evap air in 46f (in reality this is probably lower)
evap air out 38f
cond air in 67f,, out 83f
suction at bulb 36f
liquid line at receiver 91f
pressure at 58 and 250 psig
superheat 14f
subcooling 14f

give me a little bit and ill check the accuracy of my gauges (does it matter if the bottle of 404a is like 10 degrees or would it be more accurate if i warmed the bottle up?)

Gary
21-01-2008, 10:38 PM
It would be better if the bottle were warmed up and stable. That way we can calibrate to a temp that is closer to what we use the gauge for.

Gary
21-01-2008, 10:49 PM
superheat 14f


That's much better. We are very close to our target of 12F.


to be honest,, taking the suction line reading seems very fickle. sometimes i have to take the reading several times before i get a reading that seems right (i take the lowest reading).

The low side pressure/temperature is hunting because the TXV orifice is "A" instead of "AA". The orifice is oversized.

You are right to use the lowest readings.

flyboy3b
21-01-2008, 11:20 PM
It would be better if the bottle were warmed up and stable. That way we can calibrate to a temp that is closer to what we use the gauge for.
i tried is with two gauges sets and the bottle of 404a was at about 35f. all 4 gauges were in the low to high 70sw psig. i have to remember to purge those gauges though, with the lossless fittings,, it doesnt seem to want to release the pressure as well.

ill check it again in a couple hours

Gary
21-01-2008, 11:41 PM
Measure the temperature on the side of the bottle near the bottom. This is the temp that should agree with the gauges... and lose the lossless fittings.

At 35F, the gauge pressure should be 76 psi.

flyboy3b
22-01-2008, 03:50 AM
and here is the last set for today,,,
evap air in 44f,, out 39f
cond air in 70f,, out 87f
liquid line at receiver 93f
suction line at bulb 37f
pressures at 60 and 250 psig
supheat 14f
subcooling 11f

sptyagi
01-09-2008, 05:18 AM
hi i am sptyagi from india . i have ref system with r23 and 404 a cascade system . same problem i also faced in r23 system after repairing the fitting and recharging. at last we analysised there was some air was trapped into the system during charging. i suggest to take out complete the gas and was the system with nitrogen then vaccume it properly and charge the fress gas. hope you will get good results.