Nest Compatibility with a Trane HVAC system

[gary527]

I am considering replacement of my Trane Nexia thermostat with a Nest.  The online compatibility checker did not have wire selections for BK or B/C which are connected currently.  Also, I have a jumper wire from RH to RC.  

Other wire connections are W2, W1, G, and Y1.  Is Nest compatible?  Thank you.

[AxelD]

Hi gary527,

Thanks for posting! I can definitely help you with this compatibility check. You're right, the Nest Thermostat doesn't have BK or B/C ports. Do you know what those wires are for? and Could you please share a photo of your wiring?.

Keep me posted. 

Regards,

Axel. 

[gary527]

It appears the BK connection is for 24V PWM operation of the blower for variable speed.  Per the manual, "this connection allows the thermostat to control the blower speeds."   The B/C terminal is the COMMON.  The Trane thermostat has RC and RH connections with a jumper.  This is the 24V feed from the furnace.  The jumper is necessary since the same air handler is being used for cooling (requires RC) and heating (requires RH) .

Unfortunately I apparently do not have permissions to upload images as I get a warning when I try.

[AxelD]

Hi gary527,

Thanks for replying! Perfect, I got it. In this case, based on all the information you provided, it looks like your thermostat might be compatible with the Nest Learning Thermostat according to the Compatibility Checker Tool. Please take note that you'll need two separate wires for RC and RH. You can't use a jumper wire in it.

Regards,

Axel. 

[gary527]

Axel...I appreciate your reply.  However, since Nest does not seem to have a connection for controlling blower speed (BK connection in this case) I believe Nest is NOT compatible with my current system.  If you see another solution to this, I would be interested.  Thank you.