How does my hybrid heating system work?
Hi, I have a hybrid heating arrangement that’s about 3 years old including a heat pump system and a gas furnace system. I’m trying to learn more about how the two systems work together. This is all Armstrong Air equipment by the way. The indoor portion of the heat pump is stacked on top of the furnace portion. The heat pump manual mentions nothing about interfacing the heat pump with a furnace. Likewise the furnace manual mentions nothing about interfacing the furnace with a heat pump. The interface comprises a generic metal box with three relays that’s mounted on the side of the indoor portion of the heat pump. The relay box is controlled by a thermostat located inside the outdoor portion of the heat pump housing. When the outdoor temperature is above 50 degrees the heat pump heats the house. When the outdoor temperature is below 50 degrees the furnace heats the house.
What I’m really looking for here is more information on the relay box. All I have is a schematic. Who’s the manufacturer? What’s the model number? Is there a manual that goes with it?
I have included three picture links below. The first shows the overall system. The second shows the relay box. The third shows the schematic. There are no other identifying marks on the relay box.
What got me started on this quest is when I attempted to test my gas furnace before the winter heating season. I could see no way to override the outside thermostat. The thermostat is mounted inside the heat pump housing and is not easily accessible without taking stuff apart. Also, I have a home backup generator system that is not powerful enough to run the heat pump. I want the ability to be able to override the outside thermostat and use my furnace regardless of the outside temperature.
As you may see, I was able to decipher the schematics enough to add my own toggle switch to bypass the outside thermostat and give me the manual control I was looking for. Still, I’d like to have a system manual or some other documentation to backup what I think I already know. Any information on this relay setup would be much appreciated. Thanks!
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