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offgridtod's avatar
offgridtod
Explorer
Feb 25, 2018

Getting Dometic Heater to run without an AC unit on roof

We have a 2014 5th wheel where the AC units were removed due to a fire in the master bedroom. We are in the process of remodeling and the main technical issues is getting the central furnace to run. We got the thermostat in the kitchen to power up but the furnace does not power on. Apparently there AC unit has a relay or something that controls the call for heat.

If anyone knows (we are in Coastal Oregon, AC is simply never needed) but heat is key. Can we bypass the AC and run the heater directly from the thermostat.

There is a four wire plug at the ceiling - Red, White/Red - connected they power up the thermostat. A black and an Orange wire remain. Suggestion to get furnace to power up?
  • offgridtod's avatar
    offgridtod
    Explorer
    Feb 26, 2018
    Wild Card wrote:
    Supply 12v DC to the blue wire and ground to the white.


    Please clarify, I don't have a blue wire or white.
  • BFL13's avatar
    BFL13
    Explorer II
    Feb 26, 2018
    If you have a "heat only" furnace and a new thermostat, the stat manual will explain how to wire it up. I have a new Honeywell RTH111 digital stat that was confusing, but tech support and some guys on here got me straight. With that one, you take the two furnace wires and put one on W and one on R-- doesn't matter which ones, and good to go. The manual does have advice about heat pump connections too.
  • MrWizard's avatar
    MrWizard
    Moderator
    Feb 25, 2018
    its probable the oem unit was a 'heat pump'
    it was the primary heating source, and the furnance was secondary and came on if/when the heat pump could not provide the needed amount of heat

    the fire probably destroyed the wiring, but if you can find the thermostat control wires and connect the correct wire back together, the furnace should work

    OR just run new 'stat' wires

    do some reasearch find out what 'heat pump' is normal for that RV
    visit an owners group and ask questions about the heat pump operation and wiring
    look up the MFG specs and wiring diagrams for the heat pump
  • agesilaus's avatar
    agesilaus
    Explorer III
    Feb 25, 2018
    What I would do is this: go to Amazon and find a thermostat. I linked to that one since people mention in the comments that they use it on their RV. Get the manual online and see if you can figure out how to wire it.

    Look at others listed there until you find one you think will work.

    I am not a HVAC tech nor an electrician so keep that in mind.

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