Hi everyone,
I have a Ruud (Rheem) thermopump with a Ruud forced air furnace. The thermopump has a thermostat (outdoor of course) which shuts the thermopump when the outdoor temperature drops below 20F. Now for my question:
Since the outside temperature has dropped to about 32F here in the northeast, I noticed a change in the way my system works. Currently, the thermopump turns on and after 5 minutes or so, the furnace turns on for several minutes, then the furnace shuts off and the thermopump stays on until the indoor thermostat signals it to shut off. That's not how it used to function. Before, the furnace would never have turned on at all at these temperature. Of course, when it's 25F, it would eventually turn on to supplement, but now, even at 35 or 40F, it turns on as described above. My electricity costs have risen due to this >:( What can be causing this? ???
Please note that a couple of winters ago, the defrost board stopped working and I bought a new one (same part number) and switched it out. Defrost cycle now works of course, but the furnace issue started after I changed the board.
Any help would be appreciated.
Are there any jumpers or dip switches on the defrost board? Maybe they aren't adjusted the way the original board was. The replacement board could be a newer version and might be designed differently. Does the furnace always start and stop in 5 minutes after the heat pump starts? That would indicate it's by design and not an intermittent problem.
You could also try bypassing the outdoor thermostat to verify it's not somehow causing the problem. Bypassing the indoor thermostat can be a little trickier, unless you know how the reversing valve operates in your heat pump, but sometimes the process of elimination can be helpful.