Heat Pump/Furnace

[mspowerman]

Our motorhome has a heat pump roof top unit with a separate gas furnace! Should the heat pump be running when we use gas furnace? The heat pump blows out cooler air.

[TominVegas]

Originally Posted by mspowerman

Our motorhome has a heat pump roof top unit with a separate gas furnace! Should the heat pump be running when we use gas furnace? The heat pump blows out cooler air.

Without knowing what unit and A/C brand you have it's tough to say. If you have the Dometic/Atwood that is in my Georgetown 5's and many of the 3 series , the manual states the following:

The unit will heat in the heat pump mode in ambient temperatures above approx. 45°F. The furnace will automatically engage at ambient temperatures below approx. 45°F.

There is also a furnace override button on the these thermostats that control the furnace that defaults to the furnace over the heat pumps.

However, I suppose that could vary. If you have two A/C units and only one furnace, it is possible I guess that the thermostat that does not control the furnace could still operate in heat pump mode while the other is in furnace mode. I'm not sure how they are wired but in my 2019 5 series, the front thermostat is the only one that runs the furnace. Some units have two furnaces though. The XL's have a different thermostat as well.

Again, it would depend on the model of the unit and even the model of the thermostat as well as could be caused a wiring, unit, or thermostat fault.

[mspowerman]

My motorhome is in storage so not sure if brand but I just have one heat pump with separate furnace. I have a push button control where you select heat pump or you can select furnace. But when you select furnace, heat pump comes on also! That may be normal but that is now how my old motorhome worked when it just had regular AC rooftop unit!

[DougW]

My 37RB works strangely as well, but it is different. When I put the front thermostat on elec heat it will run the heat pump and the gas furnace at the same time. If I set it to heat gas it will run the furnace only. The outside temp this morning was 60 deg when it did this. I would prefer to be able to run heat pump only so I don’t run the propane down since we are parked for the next few months. The rear heat electric setting runs the rear heat pump alone.

[nayther]

you may just have the heat pump fan running with the furnace. It is common for that if the fan is set to "auto", at least for mine without a heat pump, the theory is the overhead fan will circulate the heat better than the floor distribution alone. But if the heat pump is heating it will be noticeably cooler than the furnace. Just like in AC mode it will only heat the air about 20 degrees higher than ambient or space temp. as opposed to gas heat that is 120 plus

[A32Deuce]

Originally Posted by DougW

My 37RB works strangely as well, but it is different. When I put the front thermostat on elec heat it will run the heat pump and the gas furnace at the same time. If I set it to heat gas it will run the furnace only. The outside temp this morning was 60 deg when it did this. I would prefer to be able to run heat pump only so I don’t run the propane down since we are parked for the next few months. The rear heat electric setting runs the rear heat pump alone.

If you have a towd, get an Extend A Stay kit and use 20 lb bottles rather then your unit tank. Works like a charm.

[Rich5117]

On your thermostat make sure the fan is set to auto on the furnace setting. If the fan is set to any other speed it does not affect the furnace fan but will turn on the fan on the AC/ heat pump to circulate air as stated in a previous post.

[Bama Rambler]

Nayther and Rich are right, If the 'Fan' mode is set to anything other than "Auto" the A/C (Heat Pump) blower will run any time the furnace runs.