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  1. #1
    Join Date
    Dec 2009
    Posts
    7

    G-Wire on a stat

    I'm assuming "G" on a thermostat is supposed to go to 24V AC when the heat kicks on, but it doesn't. When I'm at the thermostat and switch the fan on, then it reads 24V.
    Regardless, the blower still turns on when the heating or cooling kicks on. But if one of those are already going and I turn "fan on" from the stat, the HVAC kicks into overdrive.
    Any logical explanation for this?

    Anyone know a good link where I can learn a little more in depth about the electrical workings of a typical residential HVAC system, i.e, Y, W, C, R, G? I understand their purpose, kind of, but I'm interested in the logistics. No reason in particular - just perpetually curious. Please don't tell me to go to a book store.

    Thanks, Chris

  2. #2
    Join Date
    Apr 2008
    Location
    Pa.
    Posts
    1,148
    sounds normal to me. I assume you have fossil fuel heat? If you do hvac work you should know your low voltage. Sounds like a DIY er question. So i would call a pro if there is a problem.

  3. #3
    Join Date
    Jan 2008
    Posts
    2,128
    Lots of forums like this that give DIY advice. But not here.
    So you won't have to go to the library.
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  4. #4
    Join Date
    Jul 2005
    Posts
    5,576
    Quote Originally Posted by Chris75 View Post
    I'm assuming "G" on a thermostat is supposed to go to 24V AC when the heat kicks on, but it doesn't. When I'm at the thermostat and switch the fan on, then it reads 24V.
    Regardless, the blower still turns on when the heating or cooling kicks on. But if one of those are already going and I turn "fan on" from the stat, the HVAC kicks into overdrive.
    Any logical explanation for this?

    Anyone know a good link where I can learn a little more in depth about the electrical workings of a typical residential HVAC system, i.e, Y, W, C, R, G? I understand their purpose, kind of, but I'm interested in the logistics. No reason in particular - just perpetually curious. Please don't tell me to go to a book store.

    Thanks, Chris
    I don't see this as being a particularly DIYer question, so the short answer is that on fossil fuel systems, and on some electric air handlers, the furnace/air handler itself takes care of bringing the fan on in heat mode. This is information that is found in the instructions of virtually any Wal-mart or HD t-stat that a HO might purchase, so it isn't really a huge trade secret.

    As for a detailed explanation of the low voltage system you might want to do a simple Google search. DIY info or not, there's no point in anyone typing out 10,000 words on a subject that has already been written about thousands of times. HTH.

  5. #5
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,799
    Quote Originally Posted by Chris75 View Post
    Please don't tell me to go to a book store.

    Thanks, Chris
    Go to Amazon.
    Contractor locator map

    How-to-apply-for-Professional

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

  6. #6
    Join Date
    Nov 2006
    Location
    Oregon
    Posts
    853
    Quote Originally Posted by Chris75 View Post
    Anyone know a good link where I can learn a little more in depth about the electrical workings of a typical residential HVAC system, i.e, Y, W, C, R, G?
    Thanks, Chris
    Honeywell.com has some good documentation on thermostat operation.

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