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    NinaDC's Avatar
    NinaDC Posts: 3, Reputation: 1
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    #1

    Mar 2, 2009, 08:25 PM
    Wiring for Honeywell RTH7500 thermostat
    Hello,

    I am trying to install a new Honeywell RTH7500 thermostat to replace my Robertshaw 9200 thermostat.

    The Robertshaw 9200 had the following connections:

    One yellow wire that was connected to W and Y (the wire is long and was threaded underneath the screws in the W and Y connections);
    One white wire that went to the O connection;
    One green wire that went to the G connection;
    One red wire that went to the Rc connection (that had a jumper to the Rh connection)

    I wasn't sure what type of system I had but according to the Robertshaw 9200 installation manual, this was the connection for a heat pump system with cool active reversing valve.

    The manual for the new Honeywell thermostat has a diagram for heat pumps as follows:

    Yellow to Y
    White to O
    Green to G
    Red to R

    Notice no W (whereas the Robertshaw had the yellow wire connected underneath Y and W). I programmed the thermostat according to the heat pump directions in the manual. But when I turn on Cool, I get warm air!

    I called Honeywell and the technician had to put me on hold to ask someone who came back with "Y only goes to Y, you don't need to split the wire." :huh:

    But I still get warm air. Any help or insight would be appreciated -- I am at a loss.
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #2

    Mar 2, 2009, 08:33 PM

    Do you by chance have a zoned heat pump system.

    One heat pump and 2 thermostats?
    NinaDC's Avatar
    NinaDC Posts: 3, Reputation: 1
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    #3

    Mar 2, 2009, 08:42 PM
    No, it's not zoned as far as I can tell. I just have the one thermostat and a small condo.
    acetc's Avatar
    acetc Posts: 1,004, Reputation: 79
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    #4

    Mar 2, 2009, 08:59 PM

    Put the white wire on "w" if you don't have a "o",
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #5

    Mar 2, 2009, 09:20 PM

    Ahh! A condo.

    The Robertshaw stat has a separate O & B terminal. That is not normal: Manual here: http://www.icca.invensys.Tcom/manual...w/110-956b.pdf but that's not an issue with you.

    The Honeywell Here: http://customer.honeywell.com/techli.../69-2104ES.pdf

    On page 20, you set the state of the O/B terminal. You have a wire to O/B, not O. The parameter 190 should be 0 for and O terminal. 1 for a B terminal. If they are backwards then heat and cool are reversed.

    Parameter 0170 should probably be set to 2.

    If this is really a separate heat pump

    There are some systems that connect W and Y together. Those systems usually have the heat/cool modes set at the furnace.
    NinaDC's Avatar
    NinaDC Posts: 3, Reputation: 1
    New Member
    		  
    #6

    Mar 3, 2009, 08:32 PM
    Thanks keepitsimple! Turns out I had a loose wire, tightened it and then turned it on, making sure the settings on the screen were correct. Voilą! Cool air.
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
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    #7

    Mar 3, 2009, 08:52 PM
    Cool air? I can get waay tooo much of that by just opening a window...
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