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Ecobee4 GeneralAire 1000 Wiring Help

GregMacManGregMacMan WisconsinMember
edited January 2 in ecobee


I’m hoping that someone can help me with a wiring question that I have on my GeneralAire Model 1000 flow through humidifier. I just recently installed an Ecobee4, which is working fine, and now I’m looking to hook up my GeneralAire humidifier. Previously the humidifier was hooked up using a 24v transformer, and its own digital GeneralAire E2 humidistat, and then used a current sensing relay to turn on when humidity was called for. So the humidifier was not wired directly to the furnace, which is a Carrier 58 VUA. The humidifier also has a fan that is powered by a 120v plug. This humidifier appears to be different from the other ones I’ve seen in other posts, in that it has the typical two yellow wires, but also has two red wires.

To the thermostat, I have a five pair cable running that can be used exclusively for the humidifier, so I can run a single wire or two wire setup if needed. I tried what I thought should work, which was nothing to each separate red wire, a single wire from the Ecobee4 ACC+ to one of the yellow wires on the humidifier, and then another wire from the furnace c terminal to the other yellow humidifier wire, and it doesn't work.

The thing that is confusing me is the red wires. In the prior standalone installation, I hooked up the yellow wires as instructed, and then tied the two red wires together and left it at that (which worked for years). I don't see anything in the documentation that tells me to do that with the red wires, so how I knew to do that is actually a mystery to me. I could just tie them back together and see what happens, but given the outside temps in WI right now, I’m reluctant to do that in case something goes wrong.

I’m attaching the GeneralAire page that shows the wiring options, a picture of what the wires currently look like, and a picture of how it used to be hooked up with the GeneralAire E2 humidistat. In the previous hookup picture, the red and white wires are coming from the current sensing relay, the yellow and blue are going to the E2 humidistat, and the 24v transformer power (not pictured) is going directly to the humidistat.

Any thoughts on what I might be doing wrong would be greatly appreciated.

As a secondary question and possible approach, I have 24 v power running from a plugin transformer up to the thermostat, which used to be used for the E2 humidistat. My question is, should I be using that as the source of power for the Ecobee4 and humidifier solenoid, vs the C wire from the furnace? Does it matter? I assume the only potential issue is the load on the furnace board correct?

Thanks in advance.


GeneralAire 1000 wiring page -

Not wired -

Previous standalone wiring -


  • kevinmcckevinmcc Macomb, ILMember
    edited January 3

    The instructions are awful from GeneralAire, but the I am going to assume the yellow wires are 120vac and not 24vac, so do NOT connect them to the Ecobee if they are 120vac. The 120vac will damage the Ecobee. Measure with a multimeter to verify.

    The red wires are 24vac power, they do no have any other function and the guide says do NOT connect them together or there will be damage to the humidifier, so confused as to why they are in the picture.

    If the yellow wires are 120vac, then the diagram you need to follow is 6B. You will need an isolation relay. Connect ACC+ to 24vac coil side of the relay and the other side of the coil to C on furnace. On the high voltage side of relay connect the yellow wires, one to normally open (NO) and one to the common (C). Configure the Ecobee accessory for single wire accessory.

    If the yellow wires are 24vac, you just connect one to ACC+ and the other to ACC-. Configure the Ecobee accessory for 2 wire accessory.

  • SneakXSneakX MontrealMember
    edited January 3

    In order to confirm if the wiring voltage is 24 or 120V (I agree it is really important to be sure of the source voltage), could you locate the current sensing module and find the model, GA50 would be 24VAC and GA51 120VAC.

    120VAC means following kevinmcc’s solution. 24VAC is different and easier, more like the old setup.

    Edit: according to the docs, the solenoid seems to be energized with 24VAC, which would confirm the signal source is compatible with ACC ports on the Ecobee. Still, do a double check. Don’t want you to blow your Ecobee unit...

    Then, and only AFTER 24V CONFIRMATION, do the following:

    ACC+ : yellow wire from the old humidistat (should be a Common wire)
    ACC- : to blue wire from the old humidistat (should be a 24VAC/hot wire going thru the current switch).

    Set as a 2 wires accessory. Better to check with a multimeter if the yellow/blue wires id are correct before plugging back the thermostat.

    https://support.ecobee.com/hc/en-us/article_attachments/115012369948/ecobee4_Installation_Manual.pdf (page 73)

    It will act like a dry contact switch, as 24VAC is already provided by the humidifier.

    The red wires are to be left aside because of the external power source used in your setup. Better to isolate each red wires seperately.

    Finally there is no need to use the external power source for your Ecobee, you better leave it as is, powered from the furnace.

    Good luck

  • GregMacManGregMacMan WisconsinMember

    Thank you both for your help. I agree that the GerneralAire directions are dreadful. Its odd to me that manufacturers like GeneralAire and AprilAire are not including diagrams to hookup WiFi thermostats like the Ecobee and Nest. As for why I tied the red wires together, I'm not sure, but I must have read it somewhere and it ran for years without issue, so it must have been okay.

    So the power sensing relay is labeled as model A50/24volt. While digging for the relay, I also found a very helpful sticker that must have been attached to the wires before I installed it that says - Caution! Do not connect power to these wires! Red wires: Contain 24 Vac for electronic humidistat only. Yellow wires: Use for humidistat contacts only.

    So based on this then my next step would be to use the two wire setup as you explained above, using both the ACC+ and ACC- and leave the reds alone, but tied off separately. Correct?


  • SneakXSneakX MontrealMember


    Like I said previously I would double check to locate the live 24VAC wire between the yellow and the blue ones. I am not sure if it really matters but the Ecobee docs indicate to connect the live one to the ACC- terminal. My guess would be the blue one but only probing the wires would confirm that.

  • GregMacManGregMacMan WisconsinMember

    Sounds good. I will test with my multimeter just to be safe. I will let you know the results. Thank you very much for your help.


  • GregMacManGregMacMan WisconsinMember

    @SneakX said:

    Like I said previously I would double check to locate the live 24 VAC wire between the yellow and the blue ones. I am not sure if it really matters but the Ecobee docs indicate to connect the live one to the ACC- terminal. My guess would be the blue one but only probing the wires would confirm that.

    So I did the hookup, ACC- and ACC+, to the humidifier yellows, tied off the reds separately, and told the Ecobee I had a two wire setup, and unfortunately, it didn't work.

    With a multimeter, I then tested for voltage at the humidifier when the Ecobee was calling for humidity and I get zero voltage. I assume that when the Ecobee calls for humidity, I should be getting 24 VAC at the humidifier correct?

    Just to make sure it wasn't the wire itself, I took the Ecobee off and then hooked up 24 VAC to the wires and tested it at the humidifier and the voltage was good, so it's not the wires.

    Any ideas? Is there something I'm missing at the Ecobee4?


  • SneakXSneakX MontrealMember
    edited January 5

    This setup implies that the humidifier provides the 24V from one of the yellow wire. The Ecobee ACC-/+ acts as a relay switch in two wire mode, it does not inject voltage. If not (I thought it would) you need an external power source to be inserted in the circuit

  • GregMacManGregMacMan WisconsinMember

    @SneakX I do have the 24 VAC plugin power supply that was used in the old setup, so I can use that. I'm not sure how that would be wired into the setup though.

    Adding external power makes sense, this sticker makes me nervous though. Think they mean 120 wall voltage?

  • SneakXSneakX MontrealMember
    edited January 6

    It means it is a 24VAC source that could be provided by the humidifier to any electronic humidistat.

    Like this (second diagram from the top) : https://www.generalaireparts.com/manuals/general-e2-humidistat-owners-manual.pdf

  • SneakXSneakX MontrealMember
    edited January 6

    You could integrate the power source at the blue/white wire nut

    The circuit could be like this : yellow wire - ACC+ - ACC- blue wire - 24VAC - COMMON - white wire - red wire - yellow wire

    But... I really have some doubt about the usefulness of 24VAC. It’s really hard to get a clear idea from the awful docs. Is the solenoid connected on that circuit or not ?

    Other thing I forgot to ask, are you sure the current sensing relay is functional ? Jumping the yellow wires could give you a hint.

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