404a high pressure?

[Gary]

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]

can do,
thanks

[flyboy3b]

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]

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]

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]

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]

Any idea how many CFM that fan is rated at?

[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.

[m3ae2002]

what prefer for lubrication 404a mineral or synthetic oil systems

[m3ae2002]

lubrication system with 404a mineral or synthetic oil which prefer

[Lowrider]

shouting won't get you helped any sooner!

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

[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.

[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

[flyboy3b]

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]

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]

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]

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]

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

[joshman1]

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

[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

[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.

[nike123]

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

[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

[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

[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