I was hoping I could go out in the winter (50 deg) and turn on my heat pump so it could warm the rv over several days to 70ish. Found it will call for furnace when there is a 5 deg temp difference. I thought I might be able to wire in a toggle switch to disconnect the furnace wire but the rvcomfort folks tell me that if I do that the heat pump will kick off for 2 hours due to no furnace. Anyone know of any way around having to use my furnace and just let the heat pump bring the temp up?

I would try your switch and see what it does.

Once the furnace kicks in due to the 5 degree separation setting, the HP comes on line at the 5 degree mark. Once the RV is AT the set temp, the HP will KEEP it at the set temp without the furnace coming on again. Just use the furnace for that initial heat up. Doug

Without propane on, then the furnace will not run. The problem with a rooftop A/C is they do not have a defrost mode. IN home heat pumps, they turn over to the cooling mode and shut off the outdoor fan for about 4-8 minutes every hour or so. This defrosts any built up frost or ice on the coil, while slightly cooling the house. Rooftop A/C units have a single fan motor to turn both blower wheels, and thus can not stop one. They also do not have any sort of defrost circuit. You can manually thaw your heat pump by running the cool mode for say 4 minutes, but it probably will take 15 minutes to make up as much heat as you lost in the 4 cooling. I really wish they had a coil temperature sensor, that allowed them to run the heat pump mode until the return freon line was about 20F, indicating that the coil was covered in frost. Then shut off the compressor for at least 5 minutes, and keep running the outside fan. This will use air over 32F to defrost the coils (much like a walk in refrigerator does). If that sort of system where in use, then the heat pump would work well, even at 40F outside air temps. Yet that is not how they built most heat pumps for RV's.I work on a lot of PTAC heat pumps at my work in Portland OR. They used to have a simple 40F outside thermostat, and would revert to back up electric heat when it was under 40F outside, and change back to heat pump mode around 45F. But the latest version is digital control, with a temp sensor on the freon line, so it can run more often in the heat pump mode than the electric mode.It makes a huge difference - in heat pump mode it draws about 4 amps to make 9,000 Btu's at 208 volts. In electric mode, it is 12 amps and 8,000 But's. Fred.

Doug's solution seems the best way to go. the best heat pumps regardless of what they are installed on will only provide a 20* temp difference between cold air return and supply vent closest to the HP. Given your RV has about 280 sq. Ft. of space the HP might not be able to rise the temp you are looking for in many days of running. Is the savings in propane worth the expense of electricity? Follow Doug's advice.

RVcomfort gave you an over-simplified version of what really happens. The thermostat does not know if the furnace is running or not. When there is a 5-degree separation between the set temp and room temp, the thermostat "assumes" you want or need help from the furnace. If the heat pump by itself doesn't bring the room up to the set point over a time period, the thermostat "assumes" it's ineffective and that's when it gets locked out. There's an example of how it works in this document http://www.rvcomfort.com/rvp/pdf_documents/1976497.pdf.I have like you sometimes wanted to use only the heat pump to raise the temp more than 5 degrees and found the furnace kicking on to be a nuisance. I've considered the toggle switch you mentioned, haven't done it yet. I often set the thermostat to 4 degrees above the room temp and walk it up as the room temp rises. Just another example IMO of poor design, optimized for those who don't care to understand how things work at the expense of those who do. If "electric heat" isn't working I'm perfectly capable of noticing that and switching to "gas heat".

Coleman 15K rooftop heat pump | Good Sam Community

Wayne_Dohnal
Explorer
Jul 25, 2014
The 15k RVP heat pump ramps up the heat pretty slow, but once it gets "cooking" it throws out a lot of hot air. The specs are 12,700 btuh at 47 degrees, vs. 5,600 btuh for the heat strip, using about the same amount of electrical power.
dougrainer
Nomad
Jul 25, 2014
mlts22 wrote:
I've not gotten the point of a heat pump in a RV at all because of the single motor fan design. Why not just a regular A/C and a heat strip, although the best bang for the buck is a Cheap Heat system to supplement the RV furnace, and not bother with semi-workingheat solutions from a device designed to cool the environment.

RVP HP's for the last 3 or 4 years are a 2 motor system. 1 motor for the interior and 1 motor for the Condensor. Doug
dougrainer
Nomad
Jul 25, 2014
Wayne Dohnal wrote:
The 15k RVP heat pump ramps up the heat pretty slow, but once it gets "cooking" it throws out a lot of hot air. The specs are 12,700 btuh at 47 degrees, vs. 5,600 btuh for the heat strip, using about the same amount of electrical power.

I have NEVER seen a Heat Strip on a RVP HP. You can add one, but why???????? Same with Dometic. Some models you can add a Heat Strip to the HP, but WHY spend the money???? Doug
Pirate1
Explorer
Jul 25, 2014
mlts22 wrote:
I've not gotten the point of a heat pump in a RV at all because of the single motor fan design. Why not just a regular A/C and a heat strip, although the best bang for the buck is a Cheap Heat system to supplement the RV furnace, and not bother with semi-working heat solutions from a device designed to cool the environment.
Cheap Heat was my first choice but the way my plenum is set up, there was no way I could make it work in my RV.
Wayne_Dohnal
Explorer
Jul 26, 2014
dougrainer wrote:

I have NEVER seen a Heat Strip on a RVP HP. You can add one, but why???????? Same with Dometic. Some models you can add a Heat Strip to the HP, but WHY spend the money???? Doug
Simple answer, it was automatically included with the heat pump option on my rig. Kicked in for the first time a couple of months ago after 5 years of ownership.

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