Wyze thermostat wiring to Trane system(BK wire)

Switching from my Trane thermostat to the wyze, and have 2 wires leftover because the labeling doesn’t match up with the wyze. . I have a dark blue(came from B/C) and a black wire(came from BK), those are the ones I’m trying to place. I assume the blue wire goes to the C spot because it came from B/C and the black goes to the O/B spot. Anyone know?

Or does the black wire just get capped and not used? Or maybe the * spot.

Welcome to the Wyze User Community Forum @Mlamp89!

I am most likely not going to be the one that is able to determine your specific wiring requirements. But, I know there is a user who watches the Wyze Home Thermostat category and is an expert at this kind of thing.

When they do take a look, it is going to be helpful for them to see a photo of your old thermostat wiring and the control board on the unit where the thermostat wires connect. It might also be helpful to post a photo of the new Wyze Thermostat wiring.

As a new user it is going to limit you to uploading single photos, but you should be able to reply again with another photo upload.

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Thank you for the reply. Here is the old wiring. I ended up capping the black wire from the bk spot and put the blue wire into C. So far things are working.

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Here is the wyze.

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Not an HVAC person, but 2 things:

  1. Speculation only, but I think the B/C is the Common. If that is the case then you would connect the Dark Blue to the C Port.

  2. Not sure what Trane System you have but if it is the one with the high efficiency with the ability to check the system from the A/C Compressor outside, then you need to be careful. My son has that type of unit and it requires the T-Stat that comes with it as it communicates between the Outside Compressor and the HVAC inside.

However, @speadie may be able to help here.

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Bk is a trane specific pwm driven wire. Its usage varies depending on which furnace you have, but usually it allows the thermostat to set fan speed. If your system works for you without it, then maybe you don’t need it. The wyze cannot drive it, so if you do end up noticing problems down the line, you will want to go back to a trane thermostat that uses that terminal.


Thanks @speadie. So far it’s heating, when it tested stage 2 I didn’t notice any heat but otherwise it’s working.

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