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  1. #1

    two stats to one unit.

    I am seeking help on adding a second t-stat to a single stage furnace and A/C without adding zone dampers. Its an older system occupants wants the second stat to operate the system from upstairs.

  2. #2
    Join Date
    Feb 2012
    Location
    Toronto Canada
    Posts
    1,090
    Get them a wireless one that they can carry around with them or one that can be operated from a smartphone.

  3. #3
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,772

    A better option

    Connecting two thermostats to the same system will work but it is fraught with problems.

    Instead consider something designed for just what you're trying to do. The Honeywell Prestige can be outfitted with the Portable Comfort Control. That is a portable device that communicates with the thermostat and can be set as the active control instead of the thermostat.
    http://www.forwardthinking.honeywell...c_feature.html

    Or there's the Wireless Focus Pro
    http://www.forwardthinking.honeywell.com/products/wireless/focus_pro/focus_pro_feature.html

    Last edited by kdean1; 11-07-2012 at 04:40 PM. Reason: clarification

  4. #4
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,854
    very simple. add a 6 prong relay in the furnace.

    if you live in MD i make relay fail in heat.

    y goes to coil and one of the NO contacts
    w goes on the NC set of contacts

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  5. #5
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,772
    Quote Originally Posted by gravity View Post
    very simple. add a 6 prong relay in the furnace.

    if you live in MD i make relay fail in heat.

    y goes to coil and one of the NO contacts
    w goes on the NC set of contacts

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    I understand the diagram but I don't understand how this applies to two thermostats.

  6. #6
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,854
    this way they don't fight each other.

    EX; 1 is on heat, the other on cool.

    preferably i like to use the lower level stat to run heat and the top level to run cool. i dont hook up G to the heating stat.

    If you want both stats to run both heat and cool you would need to wire a isolation relay for G so it doesn't back-feed thru the other stat and turn on AC.

    Hope this helps.

  7. #7
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,772
    I think I see what you're saying. The diagram doesn't show input from both stats. I run into this sort of wiring mish-mash a lot and it takes a long time to decipher what is is supposed to do and determine if it is doing it properly. If a wiring diagram is not provided at the unit the poor guy who services it next will be lost.
    I would still choose a Honeywell stat and the PCC as this is precisely what they're made for.

  8. #8
    Join Date
    Nov 2009
    Location
    Bismarck ND
    Posts
    86
    Ive done them the way Gravity is speaking off it will work, but leave a wiring diagram for the next pour soul!http://www.grainger.com/Grainger/RIB...ed-Relay-5LE35

  9. #9
    Join Date
    Sep 2008
    Location
    VA
    Posts
    1,762
    Isn't the Y connection to the contacts redundant if you're not connecting G?
    "The only true wisdom is in knowing you know nothing" Socrates

  10. #10
    Join Date
    Dec 2007
    Posts
    4,698
    use the Prestige with the portable remote, it will be easier in the log run.

    I have it, use it and enjoy it.
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
    Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
    from an excerpt by Paul Jacob in Sun City, AZ

  11. #11
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,084
    The Honeywell remote makes the most sense. Or buy a cheap zone panel, skip the dampers.

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