Original message
| SMB
 |  "Question for a top tech"
, posted Wed 2 May 18:03  
im working on a 75ton trane and im having some charging issues. The 2nd stage has a sight glass and seems to run fine. the first stage doesnt have a sight glass and superheat is fine, but the sub cooling is not right. The second stage runs great with a 10 degree subcooling and an 18 degree superheat 55lb suction 225 head pressure, suction line temp of 48 and a liquid line temp of 106.
the first stage has a 50 lb suction 260 head pressure suction line temp of 52 and liquid line temp of 80. if i didnt check subcooling u wouldnt think there was a problem.
my only theory is that the unit may have air in the system but i dont know how else to check the system. any help would be appreciated.thanks
andrew
|
|
Replies:
|
| kimmy
| "Re(1):Question for a top tech" , posted Sun 23 Sep 22:31
Too many questions, too many answers.
30+ years in the HVAC/R trade.
Started when equipment was repaired not replaced.
Still feel the same way.
|
| kimmy
| "Re(1):Question for a top tech" , posted Sun 23 Sep 22:29
What operation?
30+ years in the HVAC/R trade.
Started when equipment was repaired not replaced.
Still feel the same way.
|
| kimmy
| "Re(1):Question for a top tech" , posted Sun 23 Sep 22:28
What refridgerant?
30+ years in the HVAC/R trade.
Started when equipment was repaired not replaced.
Still feel the same way.
|
| chiller guy
| "Re(1):Question for a top tech" , posted Mon 7 May 09:19:
As I recall that unit has 2 Model "R" compressors. Both had unloaders but the 1st stage was not wired.
The 2nd stg is running unloaded while the 1st is fully loaded, thus the differences in pressures. However,the 1st stg pressures are a bit out of whack with the temps as you said. Air in the system is a real possibility,especially if the system has been opened. Another issue could be a liquid line restriction. How long have the driers been in the circuit? Is there a LL sol valve that could be sticking? Run you hand along the LL and feel for any sudden temp change at these devices. Your other option is to deinventory the circuit,evacuate,replace driers, and weigh in the correct charge. You decide how much of a problem you have. Keep us posted
All refrigerants are safe - All refrigerant are dangerous. The difference is YOU !!!
[this message was edited by chiller guy on Mon 7 May 09:23] |
| | SMB
| "Re(2):Question for a top tech" , posted Mon 7 May 17:49
well u guys were all right! after seeing that u all beleived there was a restriction i had no choice but to test ur theory. sure enough after pumping down the system and cutting out the liquidline drier it was partially restricted. after evacuating half the liquid line and suction (solenoid was leaking by) started up the system to find it still overcharged. reclaimed freon until i had a 200 head 50 suction 93 liquid line. running beautifuly with new drier, thanks for ur help.
|
| | shortys
| "Re(3):Question for a top tech" , posted Tue 8 May 19:22
Glad you got your chiller fixed. When a system is operating properly you should have around 10 degrees of subcooling on the liquid line. (Convert your head pressure to temperature and subtract 10 degrees).
"Best prices online on Carrier parts and IAQ products!" shortyshvac.com
|
| SMB
| "Re(1):Question for a top tech" , posted Sat 5 May 11:07
Trane M# SFHCC75 S#J8870398 2 semi hermetic comps the stage im working on also has an unloader if that helps
|
| shortys
| "Re(1):Question for a top tech" , posted Thu 3 May 21:53
It sounds like you have a bad TXV, restricted drier, or drier that came apart and lodged particles in the TXV. Air in the system impedes the ability to condense and usually results in high liquid line temperature.
"Best prices online on Carrier parts and IAQ products!" shortyshvac.com
|
| | SMB
| "Re(2):Question for a top tech" , posted Fri 4 May 07:14
Anytime ive had a restriction in the past it never acted like this. next time i work on the unit i will definately look into ur theory but i dont feel thats it.
|
| Chiller guy
| "Re(1):Question for a top tech" , posted Thu 3 May 19:01
The top guy just left and put me in charge.
What is the model number of the unit. Package unit or split system. How many TXVs?
It appears the only problem you are concerned with is the subcooling on one circuit. Otherwise everything is running fine? Are you sure you have good readings for that subcooling circuit?
All refrigerants are safe - All refrigerant are dangerous. The difference is YOU !!!
|
| | SMB
| "Re(2):Question for a top tech" , posted Thu 3 May 20:24
it didnt grab the model number but its a 1989 trane package unit. 1 txv per circuit and sure that im on the liquid line and my gauges are reasonabley accurate as well as my temperature reading device. otherwise everything else seems correct but the fact that im not getting any heat back on the liquid line with a fairly high head pressure concerns me. im kinda a perfectionist and dont just forget about something if i dont have the answer. thanks 2nd best top tech haha
|
| | chiller guy
| "Re(3):Question for a top tech" , posted Fri 4 May 19:47
You are really testing my memory going back to 89. How many compressors in this unit? Really need a model# if you want to persue this problem. I can check out the unit from my files with the Model#.I will try to help you but I need some info.
All refrigerants are safe - All refrigerant are dangerous. The difference is YOU !!!
|
| | evildberg
| "Re(4):Question for a top tech" , posted Sat 5 May 02:10
Sounds like an overcharge with a system restriction
Union Pipefitter (service) Minneapolis MN local 539
|
|
|
