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ecobee3 - 600M Humidifier - Multiple Zones

HCrewHCrew MNMember
edited February 2015 in ecobee

I have recently purchased an ecobee3 thermostat to replace one of my existing thermostats to see how well it will work in my home. I would like to use the ecobee3 to control my humidifier, but I am not sure if I can do what I want.

I have a dual zone system setup with a zone controller, two thermostats and a single humidifier control in the cold air return at the furnace. Below is a wiring diagram that outlines the current setup:


I have six wires running between the furnace and each thermostat. After reading many posts, I believe all I need to do is purchase a 6AZU2 relay and wire it between the ACC+ terminal on the ecobee3 and the C terminal on the furnace. Below is wiring diagram of the proposed setup:


Can I attach the ACC+ from both thermostats to the single relay and have it activate whenever either zone calls for the humidifier to run or would it be better to install two relays with the outputs connected in parallel?


I hope this is enough information, but if I am missing anything, please let me know.

Thank you in advance,



  • HCrewHCrew MNMember

    After trying different combinations, I was finally able to get everything working correctly. I had to attach the C wire running from the fan relay back to the C terminal on the zone controller for each zone instead of directly to the furnace.

  • arctick20arctick20 Member
    edited November 2015

    Hey Brian - I have a similar setup and am trying to accomplish the same thing. I have a HZ322 panel with 2 thermostats and 1 humidifier. My humidifier is a honeywell he240.

    Could you explain your fix to me - or if it is not too much trouble update your awesome schematics you made so it shows your final wiring layout...



  • kevinmcckevinmcc Macomb, ILMember
    edited November 2015

    Looking at Brian's 3rd diagram, the Furnace C should be tied to the same C as the Zone Controller.

    I would connect ACC+ to the 600M and run a wire from ACC- to the 600M's 24AC hot. Then the 600M would also connect to the neutral. The relay is not needed.

    If you have enough power available from your Furnace 24AC coil you can use the ecobee3 1-wire configuration that automatically connects Rc to ACC-. You would then just connect the ACC+ to the 600M and the 600M to C.

    See pages 32 and 33 in the install guide.

  • HCrewHCrew MNMember
    edited November 2015

    Hi Kevin,

    I updated the wiring diagram with the changes that I made. I had to run the other side the of the relay back to the coordinating C terminal for each zone. If you look at the connector on the zone controller, there are two holes for each terminal and I was able to add the wire to the 2nd hole.


    Here are a couple of pictures of my completed setup:



    Hope this helps, but if you have additional questions, please let me know.


  • kevinmcckevinmcc Macomb, ILMember

    Do you really need the relay though? If you run two wires to ACC+ and ACC- you can use the relay of the Ecobee to turn the 600M on and off using the extra transformer.

  • Thanks for the update Brian - our setup is similar except my zone 1 is a nest thermostat and zone 2 is the ecobee3...

    On a side note - what do you use to make those schematics??

    Thanks again!!

  • HCrewHCrew MNMember
    edited November 2015

    It is quite possible to wire the system without the relays, but I only had a one extra wire between my zone controller and the thermostats. It was too difficult to add wires since my house is completely finished and it wasn't worth the extra time or cost to do so when the relays are an inexpensive option that works well.

    When my house was built, the HVAC company installed basic digital Honeywell thermostats and the builder wanted way too much money for their solution. I was originally going to use the Z-Wave enabled Honeywell thermostats, but upon reading about smart WiFi based thermostats I ran across the ecobee3. I installed one on the main level to see how well it would work in my home and eventually I replaced the lower level thermostat. I am quite pleased with these and they work great for my home.

    The wiring diagram was created using Microsoft Visio and exported to jpg so that I could share it on the forum.


  • arctick20arctick20 Member
    edited November 2015

    Just wanted to update that I have finished off my install of the humidifier and multi-zone setup and it works perfectly!! Nest on main floor, ecobee3 on second floor with 3 remote sensors and honeywell he240 for humidifier.

    My furnace panel had a humidifier output so I wired the transformer to the panel and the transformer will only get power when the furnace is heating/fan is on. I removed the pressure switch altogether. Used a mini ball valve t to feed the humidifier.

  • 20ftsnowman20ftsnowman michiganMember

    I was able to hook up a similar system (2 ecobee3's connected to a honeywell HZ-311 zone controller. I also had six wires running to each thermostat. I connected the 5 wires per the standard method and the sixth wire to the ACC+ . At the zone controller I connected both ACC+ wires (one from each ecobee3) to one of the leads of the humidifier's solenoid. The other solenoid lead I connected to the C terminal for each thermostat in the zone controller. I had to splice this solenoid wire of course so that i could connect it to both C terminals. I powered up the furnace and then went through the reconfigure equipment menu at each ecobee and everything is working well.

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