Dometic CCC2 thermostat, decoupling HP and Furnace

[Hermes]

We have a 2016 International with dual AC/Heat Pumps. Zone 1 has the 13.5k btu unit and Zone 2 the 15k btu unit to which is associated the propane furnace.

I want to control whether I am to heat with the heat pump or the furnace by setting specific (different) temperature set-points for the heat pump and the furnace and selecting the furnace mode on the termostat.

Currently when I change a temperature set-point for the heat pump (for example lowering it so it won't kick in) it also lowers the set-point for the furnace! They are coupled - they are one and the same. In addition, even if I just want the furnace to start, if connected to shore power, the heat pump fan starts when I set the thermostat to FURN mode and the furnace starts.

Is there a way with the dip switches to decouple the Heat Pump from the Furnace? The furnace heats much faster than the heat pump, it is quieter than the heat pump and the heat comes from floor level and not the ceiling ducts which is more in tune with the physics of warm air (ceiling ducts are great when running in AC mode). In fact having the heat pump fan run while the furnace is running doesn't add anything, it pumps in ceiling air and pumps it back at ceiling level.

When connected to shore power in colder weather, I will leave the inside temp fall during the night (we prefer sleeping in cooler/cold conditions), then in the morning, fire up the furnace to bring the temperature up to a more civilized level, and then plug in an electric heater to maintain the temperature during the day if we are connected to shore power.

Anybody else experience this set-point linkage with the CCC2 Dometic thermostat? Thanks!

[Al and Missy]

This may or may not suit your needs but in my opinion, based on what I know about Dometic thermostats and AC units, the simplest way to do what you want is to install a separate thermostat for the furnace. The thermostat controls the furnace through the Zone 1 AC unit. Two wires come to the AC unit from the furnace. You could set the Dip switch for the furnace to OFF, disconnect those wires, and connect them to a separate thermostat. You can use your imagination as to how to wire it up - either use those wires or run new wires from the furnace to the new thermostat.


The thermostat would have to be a simple bi-metallic coil and switch or something like that. Residential thermostats operate from a 24VAC supply and send 24 VAC around to control things. The Airstream furnace is looking for a simple contact closure to turn it on.


https://www.rvupgradestore.com/Subur...-p/41-1068.htm

[Hermes]

Originally Posted by Al and Missy

The thermostat controls the furnace through the Zone 1 AC unit.

Thanks Al,

Did you mean Zone 2 in your reply? In my trailer, the furnace mode appears in Zone 2.

[Al and Missy]

The picture in the installation manual shows the furnace wiring going to the front AC unit. I assumed that is zone 1. Maybe it depends on where the wires are connected and how the DIP switches are set. I guess there is no difference between the two AC units so maybe the furnace DIPs are set to OFF in zone 1 and ON in zone 2 and the furnace wires go to Zone 2. Google "Dometic AC Unit Installation instructions" and see if you can find the manual. In my trailer, and several others, one furnace wire is solid blue and the other is blue with a white stripe IIRC. You could pull the inside shrouds and see which unit has the blue wires. On mine the 4 screws that hold up the shroud are visible when the filters are pulled.

[Hermes]

Originally Posted by Al and Missy

The picture in the installation manual shows the furnace wiring going to the front AC unit. I assumed that is zone 1.

Thanks, in my unit the front AC (15k btu) is identified as Zone 2, Zone 1 is the back of trailer 13.5k btu bedroom unit. It does seem counter intuitive...
Thanks for the info on the wiring!