Heat pump operating range

A heat pump is basically an Air Conditioner working backwards. Once the temp gets below a certain point it quits helping , much like the AC doesnt do much when the outside temp gets above a certain temp.

The net from the above posts (including mine) is that your HP’s are not going to do it for you but you need to look at your manuals for your thermostat and heat pump to determine what is the right thing to do.

Some heat pumps don’t have heat strips. Mine don’t but as stated, turns on the furnace. Read your manual.

Running a roofair heatpump at 7 F is asking for trouble imo.

when a heat pump become ineffective at lower temps is switches to electric heat strips built into the system to make up for deference . So you will still have heat even if it it gets below 30 degrees.

Heat pumps efficiency drops like a rock below about 40 degrees F. In part, this is due to the propensity for the evaporator (outside!) to collect ice and freeze up. When it's warmer, condensation can drain off, but below 40, it just turns to ice and clogs up everything. Don't even try it at 7 degrees.

Those kind of temperatures require your propane furnace. Even if all you want to do is warm the coach up to 40 inside, that furnace is made for that stuff.

Your heat pumps will most likely turn themselves off way before the outside temp hits 7F. I know mine will quit somewhere north of 25f (manual say 30) and AUTOMATICALLY switch over to furnace, and switch back to HP when the outside temp reaches a workable temp (manual says 35). I have to believe yours is similar.