Question about Honeywell Electronic Programmable Heat/Cool Thermostat - CT3300A100 Heater

2 Answers

Old thermostat wiring doesnt match up with new thermostat

My old wiring was as follows: G, C, R, Y, O, W2 (with jumper to E) My new thermostat is a Honeywell RTH7600 and I have no clue how to wire this. I wired it the way that I though it would go, but the heat comes on when the a/c is supposed to be on and vice versa. I'm assuming that a couple of wires are backwards, but I dont know which ones.

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  • kdlucas Dec 06, 2008

    This T-stat is fully digital. So there are setting in which I can change for different systems such as heat pump w A/C, heat only, A/C only, etc. I have changed them, but the heat is still coming on when the air should be. I am more concerned with the original wiring not being the same for this T-stat versus the old one. On the new one there is a section labeled "Heat Pump" and one labeled "Conventional." If I use the heat pump labeling, then there is one wire left, W2. the W2 area on the T-stat is under Conventional.

  • kdlucas Dec 06, 2008

    It is all electric. I have an air handler inside and one outside unit. It is a heat pump

  • kdlucas Dec 06, 2008

    The wiring is just like the old T-stat except that the old one had the white wire going to W2 and E. 

    Old wiring:
    Orange - O
    Green - G
    Blue - C
    Red - R
    Yellow - Y
    White - W2 & E
    Orange - 0

    New wiring:
    Same, except that the diagram on the plate has an outer list of terminals and an inner list. The outer is "Heat Pump" and the inner is "Conventional" I have it wired on the heat pump list, but there is not a W2 on the heat pump list so i have the W2 wired on the conventional list.

  • kdlucas Dec 07, 2008

    I changed a few of the digital setting, being that this thing is totally digital. It seems to be fine and will blow cold and hot when supposed to. I left the white on the W2 side with a jumper to the E as it was on the old T-Stat. I appreciate all of the help and for being so quick.
    Thank you.



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Look at the instuction booklet (or on the T-stat board) for a switch for the reversing valve.

Some systems reversing valves are in cooling mode when energised, some are in cooling mode when NOT energised.
You are looking for the switch (Usually very tiny, or a different jumper setting) that will change the position of the reversing valve when calling for heat/AC.

This is not a switch like the typical "ON OFF AUTO, HEAT COOL EMG HT switches. It will be on the board itself or the back of the T-stat.

Posted on Dec 06, 2008

  • Danny Clark
    Danny Clark Dec 06, 2008

    Do you have a heat pump or a gas furnace? Is it an electric furnace?

    What wire is left over, what wires are you currently using on what terminals?

  • Danny Clark
    Danny Clark Dec 06, 2008

    Ahhh thats your problem, disconnect the white from the conventional side and let me know what terminals are on the HP side.


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After you selected function 170 and set it to 7, your next function to set is 190( this is for your heat pump changeover valve) If you wired "O" to your O/B terminal, set 190 to 0, then press DONE. This should correct the problem.

Posted on May 05, 2009


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Posted on Jan 02, 2017

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