404a high pressure?

[flyboy3b]

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]

Dare we assume that the refrigerant enters the top of the coil and exits the bottom?

[flyboy3b]

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]

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.

[flyboy3b]

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]

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

[m3ae2002]

what prefer for lubrication 404a mineral or synthetic oil systems

[flyboy3b]

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.

[Gary]

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?

[flyboy3b]

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

[Gary]

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]

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/C...ion5Parker.pdf

the model # is C-A-SZ

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

[Gary]

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]

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]

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]

the new txv is coming in on monday,

thanks again gary

[Gary]

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]

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]

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

[flyboy3b]

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

[joshman1]

I think your system is not sized up properly, your condensing unit is struggling mate, good luck.

[tonyelian]

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]

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]

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.

[Gary]

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

[flyboy3b]

Did you guys/girls noticed, that this troubleshooting thread is longest in RE archive. First next to this has "only" 77 posts!

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.

i think i feel an invoice coming

[Gary]

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]

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]

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]

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]

Is the TXV still hunting?

[flyboy3b]

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]

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]

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]

actually,, its a radiator from a 65 rambler classic 550

[flyboy3b]

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

[Gary]

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]

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

[thermo prince]

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 !!

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

kind regards
T-P

[flyboy3b]

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 !!

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. . 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

[Gary]

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 !!

Why? because you have (kindly) divulged most of your knacks and techniques over the course of this 77+ post thread. . 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]

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.

[thermo prince]

It's all good - a very pleasant and polite thread which made rivetting reading! Better than primetime TV here even !

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]

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?

[knight rider]

IF I COULD I WOULD VOTE FOR GRAY USA PRESIDENT

and i am gone buy a set off his books ,

[Gary]

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

[flyboy3b]

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

its street language for homegrown pot

[Gary]

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]

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.

But in essence a really sound philosophy

[flyboy3b]

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.