How Many Thermostats for 3 Attic Exhaust Fans?

Discussion in 'HVAC Heating & Cooling' started by Briarius, Sep 3, 2008.

  1. Briarius

    Briarius New Member

    Jun 16, 2005
    Dallas, Texas
    Our house in the Dallas area has three powered exhaust fans in the attic: each fan is controlled by a nearby thermostat. There are plenty of soffit vents to feed air to the exhaust fans. The rotary resistor thermostats are impossible to synch so one fan may activate before another. It occured to me that when only one or two fans are active, they might be pulling air from the inactive fan opening versus from the soffit vents. (Eventually the summer heat is enough to activate all three fans.) Should I rewire the three attic fans to be jointly controlled from one centrally located attic thermostat, or am I making work for myself? Thanks in advance.
  2. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    It probably doesn't make a lot of difference where the makeup air comes from as long as it is exhausting the attic, but there is no reason one thermostat could not control all three.Possibly there is a common point where all three wires meet and where the thermostat could be connected.
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    The thermostatic control could be low voltage (controlling a relay) or line voltage. As long as it has enough contact capacity to trigger and run all of the fans, using one should be fine (as long as all areas of the attic are open to each other - if not, then individual controls might be best).

    Even controlling a relay, double check the contact capactity and the coil'll probably be okay, but no reason to burn it up.

    In a hot sunny location, I'd think about using a solar powered fan and save on the electrical costs. They do cost more, so you'd have to run the energy costs verses the life and purchase costs to see if it would pay off. is one I've seen.
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