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Thread: Help with wiring for Wifi Honeywell thermostat RTH6500WF

  1. #1
    Junior Member

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    Help with wiring for Wifi Honeywell thermostat RTH6500WF

    Hello everyone,

    I was wondering if someone could help me with the installation of the wifi thermostat from honeywell (RTH6500WF Wi-Fi Series). I am new to HVAC systems and I have connected new thermostats before, but this one requires a C wire for the power, however, the current thermostat I have does not have a C wire connected to it.

    Here is a picture of the old thermostat

    Click image for larger version. 

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    I was going to return the new thermostat due to incompatibility, however, I noticed there were 2 extra wires inside of the wall that were not being connected
    Here is an image of the wires I found behind the old thermostat.

    Click image for larger version. 

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    There are 4 wires coming from the black packet: a white one connected to W and a Red one connected to Rh. There is also a green and blue one not connected and unlabeled. I know the color does not necessarily represent the letter of the connector so I traced them all the way down to the basement, where the heating unit is located. Here is what I found

    Click image for larger version. 

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    Here is a picture of the inside of the unit in case it is needed.

    Click image for larger version. 

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    The are several things that confuse me:

    1.- there are 2 black packets coming from upstairs, with some wires inside of each black packet.
    2.- there is a yellow wire connected to W. upstairs at the old thermostat, that wire was white. Not sure where the yellow comes from
    3.- there is a white wire not connected to anything. I you look closely to the C connector, it looks like there was a wire connected to it at some point but then it broke (you can see the remaining tiny copper portion still attached)
    4.- Two red wires are going to the R connector, one coming from each black packet.

    I am not sure if I can still connect this Honeywell thermostat somehow or not. is there any wiring that is required? If not, I definitely need a new thermostat because on the old one, the button to increase the temperature does not work well. So is there a specific type of thermostat I need?
    Any advice would be greatly appreciated.

  2. #2
    Administrator

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    You need to find out where the other end of the wire is that connects to the old thermostat that has the red and white wires connected to it. There must be a location where this wire is join together to a different wire.


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