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    blue62topaz's Avatar
    blue62topaz Posts: 6, Reputation: 1
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    #1

    Dec 14, 2008, 09:58 AM
    Replace old thermostat without labels
    Hi. I am trying to install a new programmable thermostat from one that is not labeled. When I remove the outer cover, I see two (2) red wires, (2) black wires, one (1) white wire and one (1) tan-ish color. There is no green, yellow, blue, etc. I have replaced a few of these thermostats before, but they were all color coded. Please help me determine which wires from the older connects with the newer model wires. Thanks much! :confused:
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
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    #2

    Dec 14, 2008, 10:01 AM

    Need more info. What are the terminal designations on the old t-stat? Don't disconnect anything yet...
    blue62topaz's Avatar
    blue62topaz Posts: 6, Reputation: 1
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    #3

    Dec 14, 2008, 10:39 AM
    I don't recognize terminals or what they are. (My bad :o) All I see are wires coming through one hole from the back of the thermostat. I haven't disconnected anything yet. I attached a photo. Hopefully it is clear enough for you to recognize the connections.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #4

    Dec 14, 2008, 11:10 AM
    What kind of system?
    blue62topaz's Avatar
    blue62topaz Posts: 6, Reputation: 1
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    #5

    Dec 14, 2008, 01:49 PM

    It says Lenox, spelled with one 'n'.
    blue62topaz's Avatar
    blue62topaz Posts: 6, Reputation: 1
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    #6

    Dec 14, 2008, 01:52 PM
    Oops. It IS Lennox with two 'n'.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #7

    Dec 14, 2008, 02:06 PM
    Complete and exact model of furnace
    Complete and exact model of old thermostat

    Post both
    blue62topaz's Avatar
    blue62topaz Posts: 6, Reputation: 1
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    #8

    Dec 14, 2008, 02:35 PM

    Furnace: Lennox HP18-411U-3P
    T-stat: Lennox 72F1101
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #9

    Dec 14, 2008, 02:48 PM
    Quote Originally Posted by blue62topaz View Post
    Furnace: Lennox HP18-411U-3P
    T-stat: Lennox 72F1101

    From what I can tell that unit is about a 1984 vintage heat pump. Bad news is that someone wired it with non color code wiring which you already new. I can provide you with a universal wiring change over diagram and you will have to identify every wire you remove with the terminal it came off so as to use this universal change over diagram to transpose the old designated wires to the new thermostat terminals. Other option is to sound out each wire and see exactly where it goes on the air handler to find out exactly what it is used for. The next option is to have a professional do a on site srevice call to replace the thermostat. Sorry but under these circumstances this is all I can do.


    Look under lennox 16,18,19 series
    Attached Images
  1. File Type: pdf heat pump wiring.pdf (13.3 KB, 157 views)
    2. blue62topaz's Avatar
    blue62topaz Posts: 6, Reputation: 1
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    #10

    Dec 14, 2008, 02:57 PM

    Thanks a million for your help. I will have a professional install it just for safety.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #11

    Dec 14, 2008, 03:03 PM
    That is a smart idea. This way if they burn up the new thermostat they will have to get you a new one.
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