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Using a thermostat to turn on/off a fan.

Post in 'DIY and General non-hearth advice' started by jtb51b, Nov 15, 2012.

  1. jtb51b

    jtb51b Feeling the Heat

    Joined:
    Dec 24, 2007
    Messages:
    327
    Loc:
    Birmingham AL
    I happen to have an extra, 7 day multi-setpoint programmable, WIFI thermostat. I would like to use it to turn on and off a level to level air-share fan that will pull colder air from up stairs to the hotter basement. I can control the fan portion of the thermostat individually as well as remotely so it would work out great. I just dont know what else I would need to make it happen... Would I need an old furnace control board to use the power supply and relays? Or since I already have the 24 volt supply covered is there another way? The airshare fan is a 110 volt unit, very low amperage.. This would in some ways kinda make my wood stove into a furnace, although it would still just be heating the basement but with thermostatically controlled forced air coming from floor to floor..

    Jason

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  2. FanMan

    FanMan Feeling the Heat

    Joined:
    Mar 4, 2012
    Messages:
    313
    Loc:
    CT stix & upstate NY
    You would need to look at the thermostat specifications and see what the fan contacts are rated at. Most likely they're only rated for low voltage, so you'd need a 24V relay with contacts rated at 110V and the amperage the fan pulls. Such things are readily available at Radio Shack or Digikey. You shouldn't need a furnace control board.

    A simpler solution (I realize you already have the thermostat, though) would be to use a line voltage thermostat. That's what I did for a similar setup, moving hot air from above the stove into an adjacent bedroom..
  3. seige101

    seige101 Minister of Fire

    Joined:
    Mar 25, 2008
    Messages:
    535
    Loc:
    Palmer, MA
    You need a simple relay. I highly recommend a RIB relay http://www.electrocontrolsupply.com/FUNTIONAL DEVICES_RIB2401B.html

    They only need 24vac to power the coil and, the contacts them selves are rated 20 amps.

    You could either use the t-stat to well run the fan like a t-stat or use the fan setting. You will need to use the 24vac transformer you have.

    If you want to go this route private message me i will help you with any questions or wiring diagrams
  4. ROVERT

    ROVERT Member

    Joined:
    Aug 7, 2012
    Messages:
    120
    The transformer and relay approach will definitely work. I'm using an attic fan thermostat to run the fan that moves hot air from the room my stove is in. It is a cheaper, simpler solution but may not work so well if you don't have a convenient place to hide the t stat.
  5. jtb51b

    jtb51b Feeling the Heat

    Joined:
    Dec 24, 2007
    Messages:
    327
    Loc:
    Birmingham AL
    I like the RIB.. I am definately going to be doing this soon. I have to order the fan. I may just go with a line voltage thermostat tho, because I may give the WIFI away. I am not sure exactly what I will do but knowing the availability of a 24volt/120 volt relay is very helpful! Thanks guys. I will keep you posted.

    Jason
  6. backpack09

    backpack09 Minister of Fire

    Joined:
    Sep 10, 2007
    Messages:
    551
    Loc:
    Whitman, Mass
    I use an old thermostat a couple of computer fans and a 12v dc transformer from an old cordless phone to cool the inside of my entertainment center... If that helps you with anything at all...

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