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Hydro air thermostat settings

stehman Member Posts: 2
I have a propane fueled Viessmann hydroair system with several air handlers. One of the air handlers is having issues. When the fan is set on auto and the thermostat is calling for heat, the fan is not starting. If the fan is set to on then the air coming out of the duct is warm. I was using a Nest thermostat but tried a basic Honeywell today and it is doing the same thing.
1. Can you use a Nest with hydro air. If so, are there any particular settings that would be different than a forced hot air system?
2. Any ideas as to why the fan is not coming on in the auto mode?


  • njtommy
    njtommy Member Posts: 1,105
    How is the unit wired? Is W wired to a strap on aquastat to bring on the fan or is G the only thing able to bring the fan on.

    Some pictures or explanation of how your system is wired would help.
  • HydroAirJoe
    HydroAirJoe Member Posts: 27
    Is you equipment designed to turn on the fan when there is a call for heat ? Is the Fan in that airhandler controlled by an aquastat?
    Need more info.