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Thermostat direct control of a 24V damper?

For one HVAC unit, I want AC to go to all rooms whenever the AC runs, like normal. However, I only want heat to go to a subset of those rooms whenever the heat runs. I have a 24V motorized damper in place, so it can cut off air flow to the rooms that don't need to be heated. (Don't worry about airflow rates, the system's more complicated than that, I'm simplifying for the purpose of this question.) Because the requirements for zone control are based solely on heat vs AC, multiple thermostats are not required, and the sole thermostat does not need to know anything about zones, it just needs to work as it normally would for a non-zoned house.

This should be possible using the thermostat's heat request to directly control the damper, without a zone control board acting as the middleman. Any recommendations for wiring this up so that the damper gets the 24V power it needs whenever the heat is on? (Thanks!!!)


  • JStar
    JStar Member Posts: 2,752
    edited August 2015
    Does the furnce have a Humidifier terminal? That will only be energized in heating mode and can be used to control a relay or zone damper signal.
  • synosure
    synosure Member Posts: 6
    That is a beautiful, elegant idea. I hadn't thought of it, and I love it. I'll pull the multimeter out and climb in the attic to test the "HUM" lead this weekend. Thanks!
  • ratio
    ratio Member Posts: 3,173
    Perhaps more complicated that you are looking for, but the Viconics T900 series is made to do just that - including a duct sensor to tell it what the system is doing at that moment.

    N.B. Pick the correct model for the damper actuator, the 901 for spring return, 95x for floating control, or the 92x for modulating.