I set up a two zone whole house dehumidifier system with 24v no/nc dampers, primary and secondary zones. the primary zone is controlled by a Aprilaire model 76 external control and the secondary zone is controlled by the dehumidifier itself, an Aprilaire 1870. The system is not connected to the hvac controls. I want to install a 110v auxiliary fan and I want the fan to turn on when the dampers energize. Can I use the 24v signal coming from the damper transformer to power a relay to energize a receptacle that the fan plugs into? I need the fan and dampers energized simultaneously. I have a white rodgers 90-113 fan control that fits in a 4x4 box. Can I use the 24V signal coming from the dampers? and how do I wire the white rodgers control to get 110v out?. I just need a automated on off switch. I don't want to fry the dehumidifier board or 76 controler.

Aprilaire support says I can use the 24vac going to the dampers for my 24vac IN at the white rodgers fan control. now I have 110v in and 24vac in, so all I have to do is figure out how to connect the wires to the fan control to get 110v out.

  • With the info provided a 24v relay could be used to control the 110v needed.
    – Ed Beal
    Feb 18, 2021 at 19:02
  • I agree, now I need to know what relay to use and exactly how to wire it. preferably a relay I can mount in a 4x4 box. Feb 18, 2021 at 20:01
  • The low voltage needs to be isolated from the line voltage in a 4x4. fed from the furnace circuit this is allowed for associated furnace electrical. break the hot and use the relay to connect. N.O. contact set when 24 v on relay the 120 will be available.
    – Ed Beal
    Feb 18, 2021 at 21:59
  • The furnace circuit is close by, yes I can use it. Feb 18, 2021 at 23:39
  • Thanks, you are making it simple. Feb 18, 2021 at 23:41


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