Successful installation Aprilaire 550
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  1. #1
    Join Date
    Oct 2005
    Location
    Omaha, NE
    Posts
    309
    Thanks all for the advices recently on humidifier installation.
    I installed an Aprilaire Humidifier 550 this weekend.
    A useful link is here:

    http://www.myhvacparts.com/Full%20Hu...0Education.htm

    Most of the installation is straightforward. The only tricky part is the 120V wiring for the Humidifer Transformer:

    - The A50 relay (the previous contractor installaed it) was not functioning. from my reading and talking to installer, they hate the A50 relay.

    - I have 1991 Tempstar furnaces (x2), and it was a challenge to find the 120V to hook up the transformer. I wired the 120V circuit to a "switched" terminal, which means the transformer is powered only when the blower motor runs. In my case (for those familiar with Tempstar circuit board), I used a voltmeter and watched the furnace go through a cycle and probe to see which terminal turns on with the blower on. I found #1,#4, #5.

    #1 & #4 are "upstream" from the blower circuit (#5) so I removed the jumper wire from #1 and #4 and make new connection with a winged nut. (They adise not to wire directkly into the blower motor circuit and I am not sure why not because the transformer draws very little current anyway).

    I also took (alot of ) time to clean and vacuum the burners and heat exchangers... about a cup of black soot and tar removed. I used a 1/2" hose (clear type) attached to a vacuum machine to clean the furnace.

    ANYWAY WORKS GREAT!!!
    cn
    Omaha NE

  2. #2


    This is not a DIY site (link below), so please post accordingly.

    Thanks for your understanding.

    (we can't help DIY, due to site rules )

  3. #3
    Join Date
    Apr 2004
    Location
    Bartlett, IL
    Posts
    6,619
    Originally posted by cn
    Thanks all for the advices recently on humidifier installation.
    I installed an Aprilaire Humidifier 550 this weekend.
    A useful link is here:

    http://www.myhvacparts.com/Full%20Hu...0Education.htm

    Most of the installation is straightforward. The only tricky part is the 120V wiring for the Humidifer Transformer:

    - The A50 relay (the previous contractor installaed it) was not functioning. from my reading and talking to installer, they hate the A50 relay.

    - I have 1991 Tempstar furnaces (x2), and it was a challenge to find the 120V to hook up the transformer. I wired the 120V circuit to a "switched" terminal, which means the transformer is powered only when the blower motor runs. In my case (for those familiar with Tempstar circuit board), I used a voltmeter and watched the furnace go through a cycle and probe to see which terminal turns on with the blower on. I found #1,#4, #5.

    #1 & #4 are "upstream" from the blower circuit (#5) so I removed the jumper wire from #1 and #4 and make new connection with a winged nut. (They adise not to wire directkly into the blower motor circuit and I am not sure why not because the transformer draws very little current anyway).

    I also took (alot of ) time to clean and vacuum the burners and heat exchangers... about a cup of black soot and tar removed. I used a 1/2" hose (clear type) attached to a vacuum machine to clean the furnace.

    ANYWAY WORKS GREAT!!!
    cn
    Omaha NE
    Whoops, you just flubbed that one up by tying it into the blower, now it's gonna be producing back emf. It'll work for a while like that, but soon you'll be replacing that blower motor, hope they have em on sale.

  4. #4
    Originally posted by 2hot2coolme
    Whoops, you just flubbed that one up by tying it into the blower, now it's gonna be producing back emf. It'll work for a while like that, but soon you'll be replacing that blower motor, hope they have em on sale.
    That's not the only thing that going to lose it's smoke!

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