Drew
29-03-2014, 12:30 AM
Another strange one........
Had a job yesterday where on a cold room normally running at -5c sst on 134a, for a 2c room we had a suction running at 0c with an acceptable superheat of 7c. The room was at 4c so suction seemed high. The sight glass was also showing short and hp was down but it was cold ambient with no hp fan control. I assumed the compressor was not pumping correctly so pumped it into a vacuum and watched it hold a 20 inch vac for half an hour . All ok. I then noticed oil on suction rotalock , tightened and topped up 134a. Suction still at 0c with similar superheat, clear sight glass. I then opened texv a turn which brought the suction up to 5c and noticed system flood back? Then shut down valve which lowered suction to -5c? Super heat up to 10c. During this all I thought I had heard a 'tick' coming from the condensing unit and so am not sure whether me shutting the valve or the tick noise lowered the suction. Could I have freed up a stuck suction valve which would have shown my effeciency test to be ok by still holding a vacuum, but still be inefficient? Or could my valve be playing up? An expansion valve shouldn't influence my evap pressure unless it's flooding back or starving and in this case I seemed to have two different evap pressures with acceptable super heat. One pressure however to high and the other correct. I'm confused with the fact that a texv shouldn't influence my evap pressure or a compressor that had all the signs of not pumping properly , but an effeciency test proved it to be ok and then it suddenly started pumping and suction dropped?
what a way to end the week.
any ideas!
Had a job yesterday where on a cold room normally running at -5c sst on 134a, for a 2c room we had a suction running at 0c with an acceptable superheat of 7c. The room was at 4c so suction seemed high. The sight glass was also showing short and hp was down but it was cold ambient with no hp fan control. I assumed the compressor was not pumping correctly so pumped it into a vacuum and watched it hold a 20 inch vac for half an hour . All ok. I then noticed oil on suction rotalock , tightened and topped up 134a. Suction still at 0c with similar superheat, clear sight glass. I then opened texv a turn which brought the suction up to 5c and noticed system flood back? Then shut down valve which lowered suction to -5c? Super heat up to 10c. During this all I thought I had heard a 'tick' coming from the condensing unit and so am not sure whether me shutting the valve or the tick noise lowered the suction. Could I have freed up a stuck suction valve which would have shown my effeciency test to be ok by still holding a vacuum, but still be inefficient? Or could my valve be playing up? An expansion valve shouldn't influence my evap pressure unless it's flooding back or starving and in this case I seemed to have two different evap pressures with acceptable super heat. One pressure however to high and the other correct. I'm confused with the fact that a texv shouldn't influence my evap pressure or a compressor that had all the signs of not pumping properly , but an effeciency test proved it to be ok and then it suddenly started pumping and suction dropped?
what a way to end the week.
any ideas!