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    kennysports's Avatar
    kennysports Posts: 5, Reputation: 1
    New Member
    		  
    #1

    Jul 17, 2008, 12:47 PM
    Changing thermostat
    I bought a honeywell ct8775c1005 thermostat model to replace an old 1970's thermostat. HOwever, there are three wires that connected the old one that controlled heating and air conditioning and the fan.


    I connected red wire to Rh and Rc... Green to G... and white wire to W. There's a slot for Y which is supposed to control COOLING, but I only have 3 wires.

    The digital temperature works and heat works when I turn on the Heat, but when I switched to COOL on the mainswitch in the basement after the winter, the temperature reading disappeared, and the AC does not turn on.

    The heating seems to work, but when I switch to COOL downstairs, the digital reading on the thermostats disappear. There are two thermostats I installed replacing the old ones. DO you think one of the thermomemters should have the White wire connected to Y to control Cool, while the other one should connect the White wire to W to control heat?

    Can the white wire be connected to BOTH the W and Y??
    wmproop's Avatar
    wmproop Posts: 3,749, Reputation: 91
    Ultra Member
    		  
    #2

    Jul 17, 2008, 02:54 PM
    Thinking you have the wrong (new tstat), ask for a tstat that is for a 3 wire system
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