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Feature or Problem?
Our Bus (1998 CC) is parked at the house and is hooked to a 50 AMP service. The three Dometic roof air units are set to COOL mode at 80 F ( Arizona) using the Comfort Center. Last night the tempertaure dropped to the mid 30’s. The fans on the roof units came on!! The Webasto is NOT turned on and there is no evidence that it tried to fire up.
So, is this a feature or a problem? The heat pumps do not work well below 40 degrees so it would not make sense for them to come on automatically at low temperature. What am I missing?
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5 Replies
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I am assuming your RTUs are controled by SMX controls. If so, my SMX controls must either be set for the RTUs OR auxilary heat but cannot simulataneously do both. Marathon has set my RTU’s to either cool or heat but only down to about 48 degrees outside temperature. Any colder and I must put each controller in the AUX mode and either use 110V baseboard heat or the 24V Webasto. I would guess if you get a swing in temperature that extreme you are in the same boat. Hope this helps.
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John,
Your Comfort Control (I assume you don’t have SMX) may have been set with each of the 3 zones to both AC and Heat. I don’t remember from my single thermostat Comfort Control if it has the capabilities of activating both heat and AC, but that could be what happened. As you mentioned, at 30 degree’s the heat pump function will fail and when it does, the fans will run.
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Tom,
I do not believe the Comfort Control Center can be set to more than one mode at a time for each roof unit. I know it is a stretch but, is it smart enough to switch to HEAT PUMP mode when the temperature is a lot less than the COOL setting? The screen still indicated that it was in COOL mode.
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John,
Your Comfort Control Center controls three zones and each zone can be set to it’s own mode (Fan, Cool, Furnace, Heat) independantly. A temperature setting must also be chosen. Fan speed can have up to three choices depending upon the mode selected.
If all three zones are set to Cool, fan set to auto, and the temperature is set to 78º, the roof airs should not come on until it is above 78º in that zone inside the coach.
The problems I can throw out to you are: your selected temperature may be too low, one of the zones may be set to Heat, the Comfort Control Center is not working correctly, a temperature probe is bad, or a control board on one of the roof airs is not working correctly. I experienced a bad control board on my bedroom roof air this summer and had all kinds of wierd stuff happen before it was correctly diagnosed. Replaced the roof air and all was solved.
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I have a 99 40′ CC with 3 roof A/C units and the comfor control center thermostat.
If I have my thermostat set to Furnace (the Webasto) and try to put one of the other zones on cool it will not work.
Secondly, I have 3 zones on A/C or Heat pump but only two on Furnance. To run the Webasto I use zone 1 the kitchen cabinets and front dash and zone 3 the bedroom, zone 2 does nothing when set to Furnance.
I think you can put any of the three zones in any combination of A/C or Heat Pump or Fan Only simoultaneously.
I have heard a lot of talk about the Heat Pumps not working down below certain temps. Mine will wokr down to freezing but when the temps get to 28 the units will cut off, fan and all. They stop working completly.
Set to cool at 80 degrees and fans comming on at 30 degrees is wild. Don’t know about this one.
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