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Williebago's avatar
Williebago
Explorer
Nov 20, 2019

Why no continuous furnace fan option?

I am on my second 35 foot gasoline powered Class A coach and both have two roof mounted Dometic heat pumps and a separate gas furnace, one an Atwood and the other a Suburban. The heat pumps have high/low/auto fan positions, but the furnace only has an auto position. Why is this?

My stick and brick house furnace has a continuous fan setting. It would be nice when it was really cold to have this option so the furnace could supply some warm air to protect the water tanks and piping in the basement, whether driving or parked and plugged in.
Class A

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  • Johno02's avatar
    Johno02
    Explorer
    Nov 20, 2019
    Understand your problem exactly, and the other reasons are all correct. We use two small Vornado fans, one on the doghouse in front, and one in the back bedroom blowing to the front. We have found that these make a lot of difference in keeping temps more even all over the coach. And it's a cheap solution.
  • Sam_Spade's avatar
    Sam_Spade
    Explorer
    Nov 20, 2019
    Williebago wrote:
    but the furnace only has an auto position. Why is this?


    Under what conditions are you likely to use the gas furnace ?
    When you don't have access to shore power and don't want to run the generator all night, maybe ??

    The gas furnace is there mostly for use when on battery power only.
    Running the fan continuously would accomplish little to nothing BUT would sap the batteries rather quickly.

    It is designed that way on purpose.
  • dougrainer's avatar
    dougrainer
    Nomad
    Nov 20, 2019
    RV furnaces are designed to operate with a specific RPM. That is so the safety controls will function as designed. IF you had a continuous fan mode, that means the safety controls would have to be bypassed. COST is a factor. Home systems cost a lot more and the control systems cost a lot more. When you have that level of cost, the Home systems are designed to have continuous fan operation. Roof top RV AC/HP units do not have RPM needed safety systems. So, they can have whole RV fan operation. COST is the reason. Doug
  • rockylarson's avatar
    rockylarson
    Explorer
    Nov 20, 2019
    The air flow from the fan moves the sail switch that tells the furnace that it is ok to release propane and start the igniter.
    Not an expert but that is my simple understanding. Somehow I don't think having that safety feature open or not functioning is not advisable.
  • Argosy24's avatar
    Argosy24
    Explorer
    Nov 20, 2019
    A combination of the relatively small mass of the motor home cooling quickly, batteries dying even quicker, and a motor that isn't rated for continuous duty?
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Nov 20, 2019
    THe fan burns 12 volt battery power. not 120 volt Mains power (though the converter does convert it) .. Frankly I do not know why no full time fan.

    I do turn one AC on fan only for air circulation from time to time.
  • rk911's avatar
    rk911
    Explorer
    Nov 20, 2019
    we leave the fan on 24/7 at our home, too. don’t know but my guess is that our homes hold the heat better and longer than in our RVs. they cool down a lot faster and a running fan would just blow cold air.

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