Old Rheem - High Pressure Trips in Cooling When Overnight ODT < Setpoint
As discussed in other threads, I've had recent issues with 1999 model Rheem HP condenser tripping high pressure switch in cooling mode. It appeared to be corrected when I switched back to a MERV 8 filter and sealed a 17cfm return leak, which may have allowed hot, moist air to enter the air handler from the attic.
Not so corrected! The overnight temps here in Central Florida have finally started dipping below 75*, but still need cooling to maintain comfort due to high overnight humidity. I have not switched my "manual" tstat to heating, and probably won't, unless it gets really cold in January as it did 2 years ago.
It seems if I keep the tstat at 75* during the day, then turn it down late in the evening to 72* or so, to keep it just below the overnight ODT, it keeps running like a charm, day and night. But, if i forget to lower the tstat, or don't do it until really, really late (like last night), the high pressure switch will trip if the overnight ODT is below the setpoint.
I'll likely call my home warranty company sooner or later, if I get really tired of going out to push the red button when i forget to lower the tstat setpoint. In the meantime, does anybody have a clue as to what may be causing the high pressure switch to trip in cooling under the conditions described? I'd like to give the home warranty tech some suggestions as to what he can check, being as he likely won't be able to duplicate the conditions during daylight hours.