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    tirrick's Avatar
    tirrick Posts: 1, Reputation: 1
    New Member
    		  
    #1

    Jun 28, 2008, 08:47 PM
    Replacing a Honeywell T8575D2003 with a Honeywell RTH8500. Having trouble with wires
    I'm replacing a Honeywell T8575D2003 with a Honeywell RTH8500. Didn't think there would be issues, manuals are all straight forward. However when I removed the T8575, the wiring set up did not match what the RTH8500 was expecting.

    The T8575 has 8 wires connected as follows

    < 1 50/60hz White
    24v < 2 Com Green
    3 Heat Yellow
    4 Cool Orange
    5 Sw/Op
    < 6 Com Brown
    Fan < 7 Low Red
    < 8 Med Blue
    < 9 High Black
    10
    11

    How does these wires match up to the contacts on the RTH8500? The RTH8500 uses the NEMA thermostat wiring guidelines TStatWiring

    Any help would be appreciated. Thanks
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #2

    Jun 28, 2008, 11:34 PM
    In many cases the original installers did not follow the standard wiring code. You might end up tracing all the wires back to where they go on the unit,see what color does what, and wiring accordingly.

    This could save you from having short circuits and damage to the syatem or new thermostat.


    The old one is a fan coil stat.

    http://customer.honeywell.com/techli.../95c-10897.pdf

    The new one is not but could probably made to work.

    http://customer.honeywell.com/techli.../69-1902EF.pdf
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