Original message
| jamesb69
 |  "walk-in cooler"
, posted Sat 2 Sep 14:08  
I've been working on a wallk-in cooler and going crazy. any help would be nice. it was down when i got to it, i got stuck with it. it is doing something i have never seen. the txv is shutting off the refridgerant and it's shutting off on low pressure. it is a new txv, it will run for a while and then when it gets close to temp the txv shuts completely and won't release the gas to come back on. sometimes it will run for awhile, sometimes it runs for just a few minutes. it's a one ton copeland comp. it has 409a in it, the txv is for r-12 would that make a difference. is 409a a sub for r12? the sensing bulb is in the correct place. it will pump down to a vacuum if the low press. switch is jumped out and will will stay that way until the pressure slowly creeps back up to reset the switch, but goes right back down again. everything has been replaced out of desperation(pressure switch, txv twice, liquid line solenoid valve, filter driers) what could be causing this??
James
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Replies:
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| Chiller Guy
| "Re(1):walk-in cooler" , posted Tue 5 Sep 08:20
R-409 is one of the replacements for R-12 so the TXV should be OK.
For what it is worth, I have been through this situation many years ago. The problem then, WET system (moisture). As the temp at yhe TXV dropped the moisture would freeze and plug the valve and shutdown on LP swt. As the box (and valve) warmed up the ice would melt and everything would work fine for a while.
Since you tried everything else look for the common denominator (refrigerant). Try deinventoring the system, pull a good vac, replace the drier (and maybe the charge) and recharge the system. Since you inhereted the system you do not know what practices were used in the past and R-409 can use a synthetic oil which likes water. So a litte water in the oil, in the tubing, a poor evacuation, etc. can add up.
Let us know how you make out!
All refrigerants are safe - All refrigerant are dangerous. The difference is YOU !!!
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| | jamesb69
| "walk-in cooler" , posted Tue 5 Sep 11:01
thanks for the info, it sounds like you are correct. i'm currently pumping it down for 24hrs and will charge it tomorrow and see what happens. after every part has been changed it has to be moisture. i hope. i will let you know what happens.
James
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| bama 101
| "Re(1):walk-in cooler" , posted Sat 2 Sep 17:42
what controls the liquid line valve?
is it a wall or box thermostat? --t-stat cuts off L Line solenoid and it pumps down.and looks like a bad txv
or are they using cut in and cutout? (i doubt it)
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| | jamesb69
| "Re(2):walk-in cooler" , posted Tue 5 Sep 07:31
t-stat is in control of liquid line solenoid, when it closes unit pumps down to shut off on low suction and cuts back in on pressure rise, i replaced solenoid valve and coil to be sure, i also replaced txv. i guess i will replace it again?!? i know it's the txv closing all the way, but i don't understand why. can you use r12 txv with 409a? i'm about to change the whole evaporator unit. t-stat is wall mounted with probe inside cooler. when this happens the solenoid valve is open so i know its not the problem.
James
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| | jamesb69
| "Re(3):walk-in cooler" , posted Thu 7 Sep 13:49
success, the cooler is working like it should. it was moisture all along. after i pulled it down for 24hr and recharged with fresh gas, it ran perfect and has maintained temp ever since. thanks chillerguy for the help, this site is the greatest thing since sliced bread.
James
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| | chiller guy
| "Re(4):walk-in cooler" , posted Thu 7 Sep 19:24
Glad I could help. Just remember,"even a blind squirrel finds an acorn once in a while".
All refrigerants are safe - All refrigerant are dangerous. The difference is YOU !!!
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| | beginner
| "Re(4):walk-in cooler" , posted Thu 7 Sep 18:06
I use 409A for R12 units and it just works fine. Good to hear that you found the culprit (moisture).
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| | HVAC
| "Re(5):walk-in cooler" , posted Fri 8 Sep 09:42
It does sound like you have a little air in the system. You also said that you just got this call and it was down. You might want to check the size of the TXV on that coil. Been on some freezer where someone must have put a valve on that they had on the truck. Does the box ever reach the temp you need?
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| | jamesb69
| "Re(6):walk-in cooler" , posted Fri 8 Sep 13:37
it is the right txv, and as of today it's running 2days straight with no problems, we run it at 40degs. it's used for drug samples.
James
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