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  1. #1
    Join Date
    Jun 2019
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    Whole House Humidifier Wiring

    I went to HVAC school many years ago and finished it and did that for a little bit mostly troubleshooting having an electronics background before going there with being sent out for service calls, but ended up getting a job I could not pass up that I thought I would never get. So I am not sure if you would call me a "DIY" or not. A family member had their entire system replaced this summer due to age and wish I would have known due to who installed it I was there the other day correcting the mistakes after many calls were made to them getting dates they would come out to do correct them and then cancellations. I would say what the mistakes were and I am not some know it all, but this was common sense and I know if I said what I had to do the other day this thread would go on with laughter.

    Their house is very large and had a fan powered humidifier installed (some mistakes I corrected the other day) and it is of course wired to the "common" and the "HUM" on the control board. Of course it has the control mounted on the return to sense humidity so it does not over humidify the house and keeps it at the proper range, which I am sure you all know. Problem is and I am sure you know this too it will only turn on when their is a call for heat this way and it is losing ground keeping humidity where it should be as I found out today going over there again. So basically I wanted my family member up and running doing a start up on the furnace for safety and getting all this corrected for them.

    I would like the "Pro's" to chime in on this one if you don't mind because I let them know I did all this the other day today and got "it will not work with that furnace" with what I want to do. They went with an 80% furnace that has a DC Motor that runs all the time at I believe 30% to keep the air moving and it is set up that way running the blower all the time 24/7.

    Here is my plan... With it not keeping up with the house the way it is wired in since it has the DC Motor going all the time is to take the "HUM" wire and put it to the "G" on the blower motor terminal so it can run when it wants to keep humidity where it should be regardless of a call for heat or not. Then once the control on the return is satisfied it will always maintain that level.

    I also know I can add in a transformer too and wire it directly to that and let that be part of the control circuit with the control on the return and not use the terminal block on the furnace at all.

    I read a lot of posts on here and this is my first and want to put up another not related to this because I was told I was wrong on this one too...

  2. #2
    Join Date
    Mar 2015
    Medford, N.Y.
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    I need a good laugh( as you said), so please let us know what you did and how many of their mistakes you straighten out?
    By you being a "not a Pro" I kinda think you do qualify for a title as a DIY'er.
    Why would you settle for excuses from the install Co when your relative is so uncomfortable?
    What are you calling a "fan powered humidifier" ?
    What do you consider a good RH% range?
    Make,model of humidifier would help.
    How about the make,model of the 80% DC motor H&C system.
    How big is "a very large house" and how big of a house will this humidifier serve?

    By all means,please post your other Q's.

  3. #3
    Join Date
    Jan 2004
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    Is a very large house 4200 sq ft or 6200 sq ft?

    Is the humidifier piped into the hot or cold water line?
    Contractor locator map


    How many times must one fix something before it is fixed?

  4. #4
    Join Date
    Aug 2002
    Southold, NY
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    1st: you shouldn't be messing with it. The installing contractor can now void his warranty!
    2nd: How is wiring to G going to help. That will allow it to run in cooling as well!
    3rd: Your in over your head, A little knowledge is a dangerous thing! Get a different contractor to review the entire install and advise.

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