Multiple people including me have complained that their Dometic AirCommand heat pump fan cycles on and off - about 9 seconds on and 60 seconds off - when not producing heat. This makes it very difficult to sleep.
There is a discussion on another forum where a product manager from Dometic chimed with with the explanation and the fix.
Heat Pump question now that cold season has arrived - Forest River Forums
Hi everyone, my name is Will Troyer and I am the Account manager for Dometic (Atwood) that handles this Forest River Facility. I inadvertently gave Kary the wrong part number below and I would like to clarify that it should be part number 15092 (Not 15080). The previous number I provided is for a Non-Ducted system and wont be the correct part for your 15K ducted Air Command.
I would also like to provide a little background to this subject.
This condition does not always present itself, but it could potentially happen for some people. It really depends on what the temperature is outside Vs what the set-point temp is in the coach.
The way the existing “heat pump mode” software was written was that the fan would shut off when the set-point was satisfied. With the Thermistor located in the air-box, and the air not blowing across it, the software will think that it needs to start again when the air cools off in the AC. Once the fan starts and pulls in the room air, it satisfies the thermistor again and the cycle starts over. This seems to present itself more often where the set-point temperature is easily (or quickly) achieved by the heat pump.
To fix this, we updated the software in the replacement control board so that when the heat pump set-point is satisfied, it will put the fan on its lowest setting so that air will continue to be pulled across the room thermistor. Once the room temp is calling for heat again, the compressor will engage and potentially raise the fan speed (depending on set-point Vs actual). This eliminates all of the “Short cycling” or Off/On nuisance issues, if they are having them. Also this is the same logic that is used on the "Cool" function in the software.
Hopefully this helps you all, and I will pass this post along to our Tech service group!
My motorhome was built in April 2019 and has this issue so hopefully this will be covered under warranty.
FWIW,
Ray
Linear Mode
