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Need help installing two thermostats when only one needs a power extender!

Krieger0311Krieger0311 VirginiaMember


I'd like to start by saying I don't know much about HVAC (although a LOT more than I did before purchasing my ecobee). My home has 2 Heat pumps outside, an air handler (I think?) in the attic, and a furnace in the basement. I have a thermostat in my living room on the main floor, and in a bedroom on the top floor. I purchased two ecobee 4's- and have been using the one in the living room for months without much issue. However, the one upstairs does not have a c wire- forcing me to use the dreaded power extender.

My question is- where the heck do I install the extender? I looked at the air handler- there is no control board with labeled wires like there is on the furnace. There are colored wires, but they do not go into a control board with screws that I can easily remove/reattach to the extender. I took apart 3 different panels/coverings inside the air handler- which was about all that was visible, and never had a control board with labeled wires.

So now I am thinking maybe the extender needs to go to the control board on the furnace in the basement...? If so, will this not interfere with the other ecobee in my living room that is not using an extender? How do I identify which is which?

I noticed the furnace has a C, G, W, R, Y, and TWIN terminal- all of which have two wires connected except TWIN and G coming from two different "bundles" of wires. Obviously only one of these "bundles" has a G wire-which my upstairs Ecobee has connected- so does that mean the other bundle my other thermostat?

Let me know if I'm way off. I know thermostats aren't the only devices that use the control boards but I have no humidifier or any other equipment that I know of that would use it. Obviously it would help tremendously if I at least knew where the power extender should go for the second thermostat and then can probably figure out the rest.


  • kevinmcckevinmcc Macomb, ILMember
    edited December 2017

    You install PEK at the furnace. Do you have the make and model? The install guide will have the color code for the wires or help us locate the control board.

    Heat pump would cause you to have extra wires on C, W, R, and Y, but you would also have extra wire on O or B, and not on G. The other set could go to another thermostat, but with two systems I would suspect them to be entirely separate.

  • Krieger0311Krieger0311 VirginiaMember
    edited January 3

    Thanks for the reply! The label is an American Standard Freedom 90- but the manual I found online for that does not seem to match up with my unit very well- nor does the model number so I am not sure what the deal is there. My control board only has CGRWY and TWIN, no O, or B.

    Here is an image of the board in my furnace, as well as the wiring diagram on the door. I can get clearer pictures if they are of any help. Thanks for your time!


  • SneakXSneakX MontrealMember


    Does the bundle of wires without the green one goes to your upstair’s thermostat ? If yes the weird thing is that a blue wire connected to C is supposed to go upthere. Could it be inside the wall hidden ? Or maybe this cable goes elsewhere...

  • kevinmcckevinmcc Macomb, ILMember
    edited January 4

    The new mystery is what are the Orange, Brown, and Black wires going between the heat pump and thermostat. How are they wired at the current thermostat? Have picture?

    Green is from thermostat wire. The heat pump will not have a G, so the other green is not connected.

    You do not need PEK, Blue is C.

  • SneakXSneakX MontrealMember

    We would need to get pictures of both thermostats backplane, the furnace wiring is quite confusing. How the heck the heat pumps (or could they only be for cooling purpose ?) are connected in that setup is also an interesting question.

  • Krieger0311Krieger0311 VirginiaMember

    Well- you guys have made me feel better about being confused, that's for sure. SneakX- to answer your first question- I have no clue where either bundles of wires go. I just bought the house in June and this is the first time I've messed with the HVAC besides changing filters. As far as the orange, brown, and black wires- On my downstairs thermostat, that I converted to an Ecobee, I was told the black and brown wires weren't needed and to tape them off- which is what I did. They were originally plugged into my S1 and S2 slots on my old thermostat. The upstairs one has them as well but they are already taped off. I should also have added that I have gas heat in addition to the two heat pumps if that helps clear up any confusion around the wiring.

    Kevinmcc- So the blue "B" wire on my old thermostat is the same as a "C" wire? I guess that makes sense since I have two blue wires on the "C" terminal on the furnace. My downstairs thermostat had the blue wire connected to "C", but my upstairs has the blue wire connected to "B". I think the O/B on the ecobee confused me.

    I have attached some pictures below- but since we are here I'd like to make sure my first ecobee is connected properly- which it seems to be since it has been working fine for the last 6 months. So, I have attached pictures of my downstairs thermostat BEFORE and AFTER ecobee install to ensure I connected things correctly, and my upstairs thermostat that we are trying to connect the second ecobee to.

    Can anyone confirm the downstairs wiring looks good, and that the B wire is in fact the C wire for my upstairs thermostat and everything else just gets attached to the corresponding letter on the ecboee?

    On my old downstairs thermostat, I removed the jumper on the E/AUX terminals and the RC/R terminals, taped off the brown and black S1/S2 wires, connected the W2/Aux wire to W1 on the ecobee, and connected the orange wire that was connected to W and O/B on myold thermostat to my ecobee O/B terminal (this one confused me but that is what I was told to do). All of this can be seen in the below pictures if anyone is up for comparing them to ensure proper installation.

    Thank you all for all of your time!!

    Upstairs thermostat being converted to ecobee: https://drive.google.com/open?id=1vYFdC7ZVU2F_N88xXhSqmxMHItDUZTFZ

    Downstaits thermostat pre ecobee: https://drive.google.com/open?id=1BtCPOUkiFXgV7g7XNb3l8gMh4UISUMZJ

    Downstairs thermostat post ecobee: https://drive.google.com/open?id=11Ya7Dq2Po_fH0o9Y4eciPUvMyOZevxsU

  • SneakXSneakX MontrealMember

    From the pictures it seems your upstairs tstat is not going down to the furnace, (at least according to the cable color, white right ?). Maybe the second black cable at the furnace is going to the first heat pump (that explains why the O/B wire is not connected at the control board but seems to go elsewhere)

    Meaning your upstairs tstat would be connected only to the second heat pump ?

    In that case you have every cables needed to get it working, yes B = C, not O/B (confusing I know)

    O/B is the reversing valve of the heat pump.

    You are getting closer !

  • kevinmcckevinmcc Macomb, ILMember

    Black and Brown are for temp sensor, no need to connect.

    Blue is your C wire.

    Should be simple hookup if you got the other one working fine, they are wired the same.

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