Coleman 15K rooftop heat pump
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. ...
Forum Discussion
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.
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.
