[rdunk]

Ponch is pretty much right on this, but..........................

This subject is discussed pretty regularly, so, knowing this is one of the items that at least is covered in the technical data furnished to us by Doubletree, with our MS, I decided to find it, and to let everyone else know where to find it.

This subject is covered in the Duo-Therm "Operating Instructions" for the "Comfort Control Center", which is the control box where we select heat or A/C, zones, and temp settings. My instructions consist of 8 numbered pages, and this subject is addressed on page 7, Item F. AUX. HEAT.

Now, for those who may not have this Dometic publication, here is a direct quote for what Item "F. AUX HEAT says................
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Quote. "When in the HEAT PUMP mode, if the outside ambient temperature is measured to be below 30 degrees F. and the vehicle is equipped with a furnace connected to the Comfort Control Center, the control will automatically select FURNACE operation and the HEAT PUMP will shut down.
IMPORTANT: If vehicle is not equipped with a furnace, no heat will be available below 30 degrees F. If vehicle is equipped with a furnace and it is connected to its own thermostat, it must be manually turned ON and OFF for operation.
When this happens (referring back to auto furnace turn on), the AUX HEAT and the HEAT PUMP indicators on the LCD will illuminate. Once the outside ambient temperature is measured above 38 degrees F, the control will return to the HEAT PUMP operation, and shut down the furnace if it is connected to the Comfort Control Center. If the furnace is not connected to the Comfort Control Center, the furnace thermostat must be manually turned off."

(Yes, it says 30 degrees furnace on, and 38 degrees furnace off)

That is it!!!
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Another item that also comes up regularly is "how to reset the Control Center". The instructions for doing that can be found in the Dometic/Duo-Therm Heat Pump Installation Instructions "Manual". In my instructions that is on page 10, item 2. "System Reset".

Quote:

a. Turn the ON/OFF switch to the "Off" position
b. Simultaneously depress and hold the MODE and ZONE push-buttons while turning the ON/OFF switch to "ON". FF should appear in the LCD display until the mode and zone buttons are released"
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Hopefully, this info will be of some assistance for those who have the heat pumps, and the Comfort Control Center.