Heat pumps in freezing weather

[powderman]

Originally Posted by Arch Hoagland

We have to keep the rear bathroom vent fan going at night with a front window cracked slightly, otherwise we get a ton of water condensation on the windshield.

We will run a small electric heater set to low during the night...it was 44 degrees yesterday morning inside the coach when we got up without using the heater.

55 degrees this morning as I left the electric heater on. We use several blankets.

A good bit of that condensation is from breathing. If you just stop breathing the problem will go away.😂 Or just crack open a roof vent as hot air rises so it is more efficient than opening a window.

[nothermark]

Why not just buy a small DEhumidifier? If you get a humidistat you would find that you are running very high humidity levels for the outside temperatures. That guarantees condensation in a lot of other places you have not figured out yet. The best answer is to get the water out of the air before it condenses in a lot of places.

[palehorse89]

Originally Posted by unw1red

I agree with you. I am going to call Newmar on Monday and ask exactly the function and operating range so I am sure of my situation.

Let's also be clear that at 26 degrees, during the early morning hours, I would suspect that it could still be efficient for short periods of time.

Thanks for the feedback.

I would call the manufacture of the cooling/heating unit and ask them for a informed, direct answer, from the folks that make the unit.
Mine also heated very well in below freezing conditions on the way home from Florida in November while over nighting in Clarksburg, WV. I could see the frozen water from the unit going over the edge to the gutter. Nice and warm inside all night. Mine are 2000 year models also......still performing very well I might add.

[GaryKD]

My coach and every Newmar coach I have been in has heat pumps that have a defrost cycle. The documentation that came with the coach will explain this. One can tell when the heat pumps are in a defrost cycle because there is noise from the roof indicating they are running. However, there is no fan operation. The HVAC system will also shut down the heat pumps and switch to the propane furnace (or other appropriate furnace) when the preset parameters are met to do this. For my coach, the propane furnace will keep the utility bay at 85 degrees +!

The only Newmar coach I know of that has heat strips in the roof mounted HVAC unit is the Canyon Star. And only in the rear garage section of the coach. As best I remember, this is because the main furnace capability is not run to the rear garage area.

[Fleet]

So how do you set the controls to disable the furnace from coming on at 40 degrees?

[unw1red]

I have both zones set for HP. I can understand if you had it set for AUTO and it switched over. My caution is saving some propane, if it is indeed low, for stove use and not for heat.

What I hear some people saying is the furnace will engage and you cannot keep it from doing so unless you power the system down entirely. I can't see how that would be done without a clear warning of this operation.

[GaryKD]

Hi unw1red,
You are correct. I know of no way to not engage the furnace when the parameters are met. However, a call to Dometic might provide additional information.

Something to consider is an extend-a-stay connected to the coach propane system. One could carry a 20# propane bottle and connect it to the coach propane system. I have this setup and have used it many times. I'll use it again at the Tampa Super Show, NKK Rally.

[unw1red]

I just dug out the Dometic manuals. It says that no matter what you have selected as your heat source, the auxiliary heat (read FURNACE) will take over when the outside temperature falls below 30 degrees. The HP will take back over once the temperature rises above the 35 degree mark.

There is no way to override this setting.

[slowmachine]

FWIW, if your furnace is not connected to the Dometic thermostat, the heat pumps will run until the programmed logic in the controller board determines that it will not work at the ambient temperature. I think it took about 10 minutes to get there. The heat pumps then shut down, and an error message (something about furnace that I can't remember) is displayed on the thermostat.



Mike
2000 Holiday Rambler Endeavor 40PBD
Freghtliner XC, CAT 3126B

[Smosher]

One thing I have learned about the ceramic heaters is some of the digital new one if you loose power they won't automatic come back on. The ones that have the knob thermostat work. So if you store your motor home in storage make sure it will work if you have a disruption of power.
Steve Mosher
.

[tedgard01]

Originally Posted by Smosher

One thing I have learned about the ceramic heaters is some of the digital new one if you loose power they won't automatic come back on. The ones that have the knob thermostat work. So if you store your motor home in storage make sure it will work if you have a disruption of power.

Steve Mosher

.

My little Comfort Zone ceramic heaters are not digital, and therefore will come back on once power is supplied after an interruption. Regardless, I have my furnace set to 55 degrees, and keep the inverter on, so that in the event the heaters did get interrupted with a power loss, then the furnace (not the HP) would kick in.

Ted

[wa8yxm]

Different heat pumps different low temp cut off points. Some are indeed designed to work well below freezing.. So when someone says "no good below xx" you really need to RTFM for your unit to find out the cut off. if any.

Some of them do cut off at 32, or 35 or 40-something. But some go down to like 20.. Effiency drops as temps drop. but hey, that is to be expected.

One campground I stay at uses heat pumps for the office.. I've seen them iced over then at the end of the heat cycle it reverses briefly and defrosts.. Till it next calls for HOT.