Elec. heat v. Gas heat

A lot will depend on what you actually have. Is yours an AC unit with heat strips (assumed) or actually a Heat Pump? If it has heat strips, I doubt it will auto switch to furnace. If it’s a heat pump will depend on brand, how old, etc.

Mine has a Dometic heat pump and thermostat and it does as you state. When the outside temp falls below a set number, it will auto switch to the furnace. When it warms up outside, it will switch back.

Every MH I had before this one that had heat strips would NOT switch.

Probably the thermostat will control the function. Need to post the make and model number. Otherwise need to RTFM and check the available program options.

It must be an electric heat pump system, which is basically the air conditioner running in reverse. They are not very effective below 40 degrees. This is probably why it suppliments the heat with propane below that temperature.

Hi,

I think the OP only has a heat strip. That will function to well below freezing but will only do 1500 watts of heating. The Dometic thermostat doesn't switch to propane heating.

I added a second "dumb" thermostat which controls only the furnace. It is set to cut in if the temperature sags too much, or if the power goes off. This also allows me use the heat strip and the furnace at the same time.

If the OP has a heat pump, the control board may be sophisticated enough to switch over to the propane furnace if needed.

If someone has added a so called "cheap heat" system it will not automatically switch to propane should the power fail. Nor can you use the electric and the propane simultaneously.

So far, I have always had adequate power to heat 100% electrically. My peak load is about 7100 watts. I've boondocked at -37 C (-34 f) with two 15 amp shore power circuits. My RV is highly modified.

I can tell you how mine works. The gas vs. electric heat is controlled by the thermostat. When you turn on electric heat, the thermostat may or may not also turn on the gas furnace depending on the spread between the room temp and set temp, plus some other algorithmic behavior built into the thermostat. Heat pump vs. heat strip is controlled by a non-adjustable thermostat in the roof unit. Above the set temp the heat pump runs, below the set temp the heat strip runs. I personally don't like this automatic behavior based on what somebody else decided I want, and have added switches to the thermostat and roof unit so I can force it to do what I want it to do.

My AC has the heat strips, but I have never turned it on. 1500 watts in the center of ceiling, or plug a space heater into that circuit, and put that 1500 watts near the floor, and where I am.

The a/c is a 2019 15,000 btu Colman Mark with a heat pump.

LaTriker wrote:
The a/c is a 2019 15,000 btu Colman Mark with a heat pump.

When set to electric heat, it will not switch to gas heat at a certain outside temp. It will no longer exchange heat at about 40F as there is no longer heat for it to draw in. It will change over to gas heat when the inside temperature is 5 degrees less than the set (on the thermostat) temp, if you have propane in the tank.

Heat pump roof top units will only work to about +40 f otherwise thet freeze up as they do not have a defrost cycle. Most thermostats then switch to furnace heating then back to heat pump when the day warms.
If cost is a factor, calculate resistance heating at 5160btu/ kwh, 80 % of 91502/gal btu for propane, heat pump @ 8200btu/ kwh roughly depending on unit.
Given that in our market that propane fills are $3.50/ gallon and elec. is ,15/kw, then its equal with propane furnace heat output, no savings.
Market price for power, propane and temps. you are in are your search. It may be in some places better to heat with propane. Other places electric . heat pumps are generally best when they work.
Know the costs and how your system works.

We have two heat pumps with heat strips and two gas furnaces.
We enter the coach and it is cold. Turn on heat pumps. The gas furnaces kick in until it gets close to heat setting and the heat pumps then take over.If during the night it gets below about 40 degrees, I think or the heat pumps stop putting out enough heat the gas furnaces take over again.
If we desire we can select gas heat and it stays on gas or we can select zone one, the rear unit to be electric heat pump and zone 2 or front to be gas or vice versa. Our front unit is going to be replaced. it has bad valve. I have seen in a cold rain a lot of ice on the outside of the front heat pump, when left on electric. So I'm not sure about parameters on how they interact.