Have HVAC Questions? Ask an HVAC Expert for Answers
Hello, Those pressures do not fit any known refrigerant.. we need to address that first. Tell me what refrigerant you are using, and if you vapor charged the system or liquid charged it.
I need to know what the air temperature around the condensing unit is when you get the 85 psig pressure reading. (no refrigerant reads that low on head pressure unless it is below 30F around the condenser when the reading is taken).
I am able to train you on all this if you wish.
Thanks, ***** ***** pressure for that system should be 118 psig, given the fact of a 36F box, the suction pressure should be considerably lower than 24 psig...into the 15 psig range.
I would expect these results with a grossly over sized evaporator and condensing unit... is this a new system that you have just installed?
Next I need you to tell me if the compressor body is cool or sweating.
We can go from there.
Hello, about 50 years ago when I was still new to the business we had an AC suction line, 7/8" kinked flat (completely kinked) suction was 55 psig, when we removed the kink suction was only 5 psig higher (r-22 60 psig),
The kink in your case would have had a minimal negative effect.
Due to the high suction pressure and low head pressure I suspect the compressor valves are going bad, do a pump down test on the system.
If the valves in the compressor are bad, it will not hold the vacuum when you turn the compressor off, and the suction pressure will rise to match the head pressure (compressor off) and... you will hear a gushing sound as hot gas leaks back through the
compressor valve plate into the suction that will then suddenly get very warm.
Here is a war story for you:
About 40 years ago I found a leak at a 1-1/8" tee in a suction line between two coils, it had never been soldered... it was a very old system (prior to R12, used that flammable refrigerant, forgot name)... it had been running that way, leak free for the previous 20 or 30 years... the ridge that a tube cutter makes on the outside of the tube acted as the seal.
Thanks, ***** ***** compressor only pumped down to 8 or 10 psig (and your gauges are properly set to zero when not connected) then the compressor suction valves are going bad (depending on the type of compressor)...all compressors should be able to pump down to 0 psig suction... the older piston types routinely pump down to 20 inches of mercury on the vacuum end of the low side gauge. (Scrolls will pump down to below zero psig,into a vacuum as well, but should not be pumped down below zero).
If the low side tube at the compressor warmed up noticeably after the pump down, that points to slightly leaking intermal compressor discharge valves as well.
The pressures you gave at the outset 24psig and 85 psig also point heavily to a compressor with leaking valves.
That is right, and you proved it with the new compressor.