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jayryu
02-06-2016, 01:57 AM
It is a sandwich prep table.
Problem: not cool down under 50F

machinery detail; c/u 1/3 hp, R134a, compressor: AEA4440Y, air cooled. captube system
current condition : suction side 22.5 psi, 63.8F
after condenser 210psi, 87.5F
suction sh : 38.5F, liquid line subcool: 46.6F

condenser dT: 23.7F, condenser TD: 54.8F evaporator TD: 29F
compressor out temp: 188.7F


It is really annoying me. Please help, what is wrong?

Magoo
02-06-2016, 02:13 AM
confusing, post was small bar fridge that is a sandwich prep table.
Sounds similar to a sushi preparation cold bed slab.
More defined information would be helpfull.

jayryu
02-06-2016, 03:32 AM
It is a sandwich prep table + glass door merchandizer, whatever. Top portion is food stuff compartment and bottom is glass door fridge. Anyway problem is it is not working properly. I wonder evenif it is not overcharged, why subcooling is so high?. On top of the compressor is so hot, I couldn't stand 2 seconds to touch. Compressor is brand new.

mikeref
02-06-2016, 09:22 AM
High subcooling on your small commercial Capillary system is likely to be over charge BUT this won't be the only problem. Chances are your Cap tube or drier is partially blocked. Adding more refrigerant decreases condenser capacity and runs up the high side pressure, forcing refrigerant past the restriction.

Pull the charge. Vac and refill by weight. If suction pressure barely makes 5 to 10 PSI (with the same volume drier fitted as the original) You will have your answer.

jayryu
02-06-2016, 12:55 PM
Captube and drier are new ones. Blow tested with nitrogen and found strong draft thru captube. There seems no restriction exhists on capillary tube itself. Why subcool, condenser TD, compressor outlet temp are so high?
Is it possible there can be restriction in the system other than filter/drier and capillary tube?

Frigorista
02-06-2016, 01:59 PM
Hello. Have you think about the possibility of non-condensable gases? But if it is no restriction in the liquid line, the LP would be higher too. It seems like you have an obstruction. IŽd check carefully the liquid line and try to measure the temp. along this line.

jayryu
02-06-2016, 02:11 PM
Vacummed enoughly. There can be no incondensible. My thinking is there seems some restriction in high side. But removing drier and captube from possibility, there is only condenser. Is it possible in the middle of the condenser exhist some restriction?

jayryu
03-06-2016, 01:58 PM
With my measured value, I found weird thing. Condenser dT was 23.7F, but Gas temp before and after condenser was - condenser in : 188.7F, out: 87.5F. That means 101.2F differance. Gas has been cooled down 101.2F passing condenser only! Is it possible in physics? Then it seems some restriction in condenser coils. But I have tested with nitrogen and found very strong blowing out thru the condenser. Anyone have experience of such a thing?

chemi-cool
03-06-2016, 09:08 PM
This is a typical behaviour of some restriction, so there must be one but you can't find it,
The best tool now is thermal camera that can pinpoint it.

frank
03-06-2016, 09:21 PM
In the past I have found that R134a systems on captube control seem to floc the oil and cause blockage in the captube.

Only solution is to replace the captube or use an alternative working fluid.

Gary
03-06-2016, 10:06 PM
Remove refrigerant until the subcooling is 15F, then leave the system alone for at least an hour before taking new temperature and pressure readings.

RANGER1
03-06-2016, 10:21 PM
Remove refrigerant until the subcooling is 15F, then leave the system alone for at least an hour before taking new temperature and pressure readings.

Gary where have you been, good to see you back

Gary
03-06-2016, 11:15 PM
Had a heart attack a few years back. Since then just been mostly resting on my laurels.

RANGER1
03-06-2016, 11:20 PM
Had a heart attack a few years back. Since then just been mostly resting on my laurels.

A lot of posts over time asking about your whereabouts & books so your knowledge is very appreciated.

Gary
04-06-2016, 12:03 AM
Thanks. It's always nice to be appreciated. :)

Gary
04-06-2016, 02:36 AM
As for the books, my website host merged with another company and my website got trashed in the transition. I transferred what was left of it to a new host, but never got it working. Maybe it's an omen. Time to retire.

My son in law has talked about selling the books for me... but it has yet to happen. We'll see.

chemi-cool
04-06-2016, 11:39 AM
Good to see you Gary, take care of that old health.:)

Gary
04-06-2016, 04:49 PM
Thanks, chemi-cool.

Recoilzn
04-06-2016, 07:48 PM
is it possible compressor is not sized correctly? What heat load is there? Whats the comp amp draw vs fla.

jayryu
04-06-2016, 10:58 PM
Hi, Gary.
I did as you said, this time I have renewed cap tube again and charging R134a according to subcooling. After exactly 1 hr later I've got follong figures.

suction : 9psi, 57.5F, just after filter/drier: 120psi, 83.8F
condenser in/out : 78.4/92.4f
box temp: 62f--> 55f(during 1 hour running)
sh : 53, sc : 14.2,
condenser dT : 14 , condenser TD: 19.6.

I feel box temp going down too slowly. I couldn't stay that store anymore and left.

Gary
05-06-2016, 01:15 AM
box temp: 16.6f --> 12.6f (during 1 hour running)


In your original post you said the box temp would not go below 50F. Now the box temp is 12.6F. Is the box a fridge or a freezer? What should the box temp be?

Gary
05-06-2016, 01:49 AM
When the box temp is high, the superheat will be high. This is especially true on cap tube systems. Charging to subcooling will get you close, but fine tuning the charge (by superheat) can only be done when the box is very close to its design shutoff temp. When fine tuning for superheat, do not allow the subcooling to rise much above the 15F limit. I have gone as high as 20F SC on some systems.

jayryu
05-06-2016, 02:47 AM
I am sorry it was my mistake. The temp unit was celsius. That meas from 62f -->55.

jayryu
05-06-2016, 02:50 AM
Thanks Gary,
I'll try fine tuning next monday. I hope it will work really with my heart.

Gary
07-06-2016, 01:12 PM
Given sufficient condenser airflow and normal subcooling, the condenser TD tells us about relative load. A light load will give us about 20F TD and a very heavy load will give us about 35F TD. The current TD is 19.6F, indicating light load. Given the warm box, we should be experiencing medium to heavy load. Increasing refrigerant flow/charge will increase the load.

The cap tube is borderline undersized/restrictive, but hopefully we can force a little more flow through it (by adding a little more refrigerant) without driving up the subcooling too much. Its a trade-off.

Brian_UK
07-06-2016, 03:03 PM
As others have said, it's good to read you again Gary.

Take good care of your health, we only get one shot.

Gary
07-06-2016, 03:04 PM
I have heard of people rough charging warm cap tube systems to 30F cond TD with good results. I haven't tested this, but if the condenser is clean and the airflow through both coils is sufficient, this would make sense. If this results in excessive subcooling, that would indicate a restriction (or undersized cap tube). Anyone tested this?

Gary
07-06-2016, 03:09 PM
Thanks, Brian_UK

jayryu
07-06-2016, 05:32 PM
Charged more gas and results are as follows.

suction : 14p, 54f just before captube : 145p, 88f
sh : 41, sc : 21, condenserTD: 29

box temp : 48 f , box temp doesn,t change almost at all, for 30 min. sometimes goes up or down 0.1 ~ 0.2f.

Gary
07-06-2016, 05:44 PM
You said the cap tube was new. Is that the manufacturers recommended cap tube?

Recoilzn
07-06-2016, 09:50 PM
if im not mistaken that compressors design evap temp is 45 deg.

Gary
07-06-2016, 11:05 PM
Compressor capacity diminishes as evap temp drops. A compressor that is rated at 1/3hp @ 45F would be rated lower at 35F, say 1/4hp.

Given a system that is rated at 1/3hp @ 35F, but with (in effect) a 1/4hp compressor, the compressor would be overloaded, the suction pressure would be high and the superheat would be low. Just the opposite of this system. This compressor is underloaded, not overloaded.

It is looking very much like a restricted or undersized cap tube. This being a new cap tube, I'm thinking undersized.

jayryu
07-06-2016, 11:06 PM
Regarding cap tube , it was not recommended by the manufacturer. I used supco #2 - 79" length for that application. I have field replaced captube for 1/3 hp unit about dozen times and there never has been failure of operation in my experience.
Weired thing is when I charge a captube system, I feel the temperature of hp gas on filter/drier and if I feel warm temperature on filter/drier, I stop charging. In this manner I have never failed on cap tube system. I don't trust the amount on label because it is almost always some error.
But this unit I couldn't feel the familiar warmth on the filter/drier ever.
That is the weired thing to my knowledge.

Gary
07-06-2016, 11:23 PM
If there is a restriction in the liquid line, there will be a temperature drop at the point of restriction. That might make the drier feel cooler.

jayryu
08-06-2016, 01:06 AM
I am going to replace whole condensing unit tomorrow.

Magoo
08-06-2016, 02:36 AM
Hi Gary.
good to see you back on the forum, take care.

Gary
08-06-2016, 11:16 AM
Thanks Magoo

Gary
10-06-2016, 12:58 PM
Shall we assume the problem has been resolved?

jayryu
11-06-2016, 05:02 PM
I have postponed to replace c/u due to the cost complained by owner. I have replaced refrigerant from R134a to R414b, and measured values as follows.

box temp : 42f
suction : 18p(23f), 46.2f, filter/drier: 165p(123.7f), 85f
condenser in air: 78.7
sh : 23.2, sc : 38.7
condenser TD : 45( seems too high)

box temp cycles 37 ~ 42f.

Thanks especially to Gary.

Gary
12-06-2016, 02:11 PM
Seems extreme to me... and still looks restricted.

Peter Mackay
08-07-2016, 01:24 AM
We have had capillary restriction problems with R134a. This is a restriction caused by a off white deposit in the capillary exit. We use solid core filter, nitrogen when welding, vacuum overnight to recorded sub 100 microns yet the problem persists. Usually when charged everything is fine initially. We have been investigating this for some time and have found using a larger bore capillary helped but not 100%. Discharging R134a liquid straight from the bottle via a 0.8 capillary onto a sheet of paper, sees a mound of white goo appear which afterwards evaporates leaving the paper oiled but no moisture or other deposits!! . We have changed refrigerant suppliers and the same result. We have suspected that there may be a problem with the process of recycling R134a because this issue did not occur during the 90's when we were stopped from using R12. Would be interesting if others have similar issues with R134a on small bore capillary systems. Cheers

Peter Mackay
08-07-2016, 01:32 AM
Compressor discharge temp is extreme. Suspect your compressor has a damaged discharge valve. Try closing off suction, run down and see if it holds a vacuum.

hookster
08-07-2016, 06:33 AM
In the past I have found that R134a systems on captube control seem to floc the oil and cause blockage in the captube.

Only solution is to replace the captube or use an alternative working fluid.

Nice observation which is a visual of Franks post,

xxargs
08-07-2016, 09:14 AM
Discharging R134a liquid straight from the bottle via a 0.8 capillary onto a sheet of paper, sees a mound of white goo appear which afterwards evaporates leaving the paper oiled but no moisture or other deposits!! . We have changed refrigerant suppliers and the same result.

in my eye seems picture show massive ice build-up from air make from cool liquid R134a.


If your environment have high humidity (near 70 - 100% Rh) you can see this high level of build-up of ice (try to check using same amount and same time of liquid from cool/freezer spray (with R134a) for electronic fault search and see if build-up same amount of ice from air)

R134a itself can hold up to 1600 ppm moisture before drop of water start to shown in liquid R134a, but in mostly case if you slowly let out liquid trough small valve to free air same way as using freezer spray valve with R134a and bleed out slowly, you notice tendency to restrict and ice plugging in valve if R134a have humidity above 400 ppm moisture

If have high moisture contents in equipment, ice can make and build up extra restriction i capillary tube in point below 0 degree Celcius.

Peter Mackay
08-07-2016, 08:19 PM
QUOTE: in my eye seems picture show massive ice build-up from air make from cool liquid R134a.

Thanks for your response but this gook is as it spits out the end of the capillary and in a low humidity area. This is straight from the R134a bottle via capillary. Liquid refrigerant is exiting and evaporating then little spits of this stuff comes out like a paste! Eventually it can form a mound like in the picture. We sliced open the exit end of the capillary and start of evaporator tubing of effected systems and found a build up of dry off white gook. Another symptom is that effected systems switched off for a few days will then operate normally but with the problem re-occurring a few days later. And more prevalent with lower temp systems, all pointing to moisture but is this moisture in the R134a when supplied? I have contacted our supplier but no response... yet!

Peter Mackay
09-07-2016, 08:00 AM
I have postponed to replace c/u due to the cost complained by owner. I have replaced refrigerant from R134a to R414b, and measured values as follows.

box temp : 42f
suction : 18p(23f), 46.2f, filter/drier: 165p(123.7f), 85f
condenser in air: 78.7
sh : 23.2, sc : 38.7
condenser TD : 45( seems too high)

box temp cycles 37 ~ 42f.

Thanks especially to Gary.


Discharge temp is far to high. Replace the compressor. It has either a faulty / broken valve or leaking head gasket.

jayryu
21-07-2016, 06:09 PM
Finally I found the culprit.
During the past, I have replaced condensing unit but only resulting slight improvement.
I have found outside air sucking into evaporator inlet side. That outside air is actually condenser dischaged air.
After blocking the sucking air to evaporator, box temperature comes down fast and c/u stops at set temp.
Thanks to every person for help.

Recoilzn
22-07-2016, 06:13 AM
Finally I found the culprit.
During the past, I have replaced condensing unit but only resulting slight improvement.
I have found outside air sucking into evaporator inlet side. That outside air is actually condenser dischaged air.
After blocking the sucking air to evaporator, box temperature comes down fast and c/u stops at set temp.
Thanks to every person for help.

customer must have been bleak