diljan
06-09-2012, 07:45 AM
I've been working on a small walk in freezer this week. System had a 404 condensing unit coupled to an old R12 evap which still had an R12 TXV:). Has been running like this for two years but recently lost some gas.
I replaced the TXV and pressure tested to 2200kpa. Found several small leaks on the condensing unit. After repairing those I again pressure tested and noticed the pressure dropping steadily. About 400kpa in an hour. Shutting off the liquid and suction valves revealed that the pressure drop was on the low side. I suspected the old evap. checked thouroughly with an ultrasonic leak detector, bubble solution and an electronic leak detector with a refrigerant trace. I could not find any leaks. Checked several times but could not locate anything. Pressure still dropping from 2200. Decided then to replace the evap as well as pipework to fix oil return problems.
After installing the new evap./pipwork and pressure testing i got the same steady pressure drop. Checked everything again and still found nothing. Only a pressure drop.
So, here is my question. Could the low side pressure drop be due to the fact that the freezer room and evap were around -15degC. Outside temp was about 15deg. Would the low temp in the freezer coil cause the nitrogen pressure to drop? Or do I have some bizarre leak that I have not yet found? Is this a common problem when testing freezers. My background is AC and I have not had this problem before.
Would appreciate any advice here.
Dale.
I replaced the TXV and pressure tested to 2200kpa. Found several small leaks on the condensing unit. After repairing those I again pressure tested and noticed the pressure dropping steadily. About 400kpa in an hour. Shutting off the liquid and suction valves revealed that the pressure drop was on the low side. I suspected the old evap. checked thouroughly with an ultrasonic leak detector, bubble solution and an electronic leak detector with a refrigerant trace. I could not find any leaks. Checked several times but could not locate anything. Pressure still dropping from 2200. Decided then to replace the evap as well as pipework to fix oil return problems.
After installing the new evap./pipwork and pressure testing i got the same steady pressure drop. Checked everything again and still found nothing. Only a pressure drop.
So, here is my question. Could the low side pressure drop be due to the fact that the freezer room and evap were around -15degC. Outside temp was about 15deg. Would the low temp in the freezer coil cause the nitrogen pressure to drop? Or do I have some bizarre leak that I have not yet found? Is this a common problem when testing freezers. My background is AC and I have not had this problem before.
Would appreciate any advice here.
Dale.