Heat pump and cold weather
Asked Feb 20, 2007, 01:06 PM
I have a couple of questions about a heat pump. I guess I need to do a little explaining first.
I have an American Standard air exchanger heat pump with electrical resistance backup. The system has the original mechanical thermostat with separate contacts for the compressor and for the resistance heat. It also has an outdoor anticipator thermistor in the outside compressor.
The indoor thermostat on my heat pump is always set on seventy degrees.
When the outdoor temp falls much below thirty degrees, the heat pump's efficiency falls off and it will not heat my house. The compressor and the fan then run all the time.
When the indoor temp falls about five degrees, the resistance heat kicks in and raises the indoor temp by a couple of degrees and then kicks out again. The compressor and the fan still run all the time.
The only way to make the compressor and fan cycle properly when the outdoor temp is below about thirty degrees is to manually switch the system to emergency heat.
Don't heat pump systems have a method of having the heat pump sense the outdoor temp and automatically bring in the emergency heat without the whole system running constantly when the temp is too low for the heat pump to properly function?
I have studied the diagram of the thermostat and it's wiring, and I have looked the thermostat itself over. It appears that the outdoor anticipator is supposed to reduce the temp difference between the compressor contacts and the resistance contacts in the thermostat. Evidently, not every heat pump has this outdoor anticipator. There are no adjustments that I can see. I have searched the Internet and have found no details of exactly how the outdoor anticipator is supposed to work. I suppose that doesn't matter if I can fix this any other way.
I have looked at the specs of several of the newer digital programmable thermostats. I have found none that will make use of any outdoor anticipator. None of these thermostats offer anything that would seem to deal with this.
Isn't there any way to prevent the system from running all the time like this when the outdoor temp is too cold?