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Controlling a 110V fan from Ecobee

jeabrahamjeabraham Member

I have a switch for a bathroom exhaust fan installed next to my thermostat. I'd like to use the bathroom fan as a home exhaust fan, using the "free cooling" smart feature of the Ecobee to automatically turn on the fan when the outdoor air is cooler than the inside and it's hot inside.

What's the best way to control a 110V accessory from the ecobee? I think I could buy a 24V/110V relay, and wire the 24V side between Acc+ and C on the thermostat. Then the fan would be wired into the 110V side of the relay.

What relay should I buy for in-wall installation? Is there anything I'm missing here?

(The way it's wired in now, when you flip the switch it also activates the furnace fan, as it's a double-pole double-throw switch. I don't think I'd try to replicate this, I'd let the ecobee decide whether to turn on the furnace fan with the ventilator fan.)



  • jeabrahamjeabraham Member

    Some of these 24vdc relays could maybe work? What do you think? http://www.nteinc.com/relay_web/pdf/R14.pdf

  • EFTCEFTC CanadaMember

    It is probably easier to get a Wifi enabled switch and then use IFTTT to control it that way.

  • kevinmcckevinmcc Macomb, ILMember

    @EFTC said:
    It is probably easier to get a Wifi enabled switch and then use IFTTT to control it that way.

    Why wouldn't you use Ecobee? Ecobee has built in function for that purpose. IFTTT is not all that wonderful, way too slow and why I have abandon their service for Ecobee API.

  • jeabrahamjeabraham Member

    @EFTC said:
    It is probably easier to get a Wifi enabled switch and then use IFTTT to control it that way.

    I might do that, at least for now, only because I don't have an ecobee here yet. I found I can use apilio.io to add logic to IFTTT, so I could set it up so that the fan won't come on until the outside is cooler than the inside and the inside is warmer than some setpoint.

    My radiothermostat.com device has a URL that lets me get the temperature, I'd have to write a little program that polls it and posts the indoor temperature to IFTTT.

    The 5part combination of the radio thermostat, local polling service, apilio.io, ifttt and the smart switch worries me though. One part will fail sooner or later. A hardware relay would mean I only have one sophisticated online thing to worry about -- the ecobee.

  • LarrylLixLarrylLix Northern Southwestern OntarioMember

    Try to avoid cloud services for HVAC completely. Not a good idea.

    You need to go to an HVAC supply supply store and get a standard isolation relay. They run on 24vac input andcan switch fan motor loads, reliably. The thing about these standard reays is they are completely quiet running on a heating element, but that creates a time delay of a few seconds to a minute or more. They are cheap..maybe $12-$30 and designed for the job.

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