Solved: Google thermostat (6 wires). Need help.

[klamont9]

We recently bought a 2nd home in FL, so I want to control my temp from afar.  The house has 2 thermostats and the first Nest was easy to install.  It had 4 wires and works perfectly.   I’ve also installed 2 at our main house with no issues.   Both were 4 wires.  

The second Thermostat in FL has 6 wires.  I took a pic beforehand, but still don’t know how to set it up.  I’d love some help!

W1 = White

BK = Black

G = Green

Y1 = Yellow

B/C = Blue

R/H = Red (it also has a jumper to R/C)

I don’t know what to do with the Black and Blue wires.  

Moderator edit: Subject updated for clarity and findability.

[jb76]

Hi - Here is how typically wiring is done for thermostats (your FL house probably has an AC/Furnace with this same control board layout):
W - Heating control

BK = Black (secondary filter/pump for HVAC)

G = Green (Fan control - to circulate unconditioned air in home)

Y1 = Yellow (AC/compressor control)

B/C = Blue (Typically used for aux. power to Nest thermostat - connected to 'C' on furnace/AC control board) - important to keep enough charge in Nest Thermostat (3.85 V or higher).

R/H = Red (it also has a jumper to R/C) - Furnace control and power back to Nest when furnace is turned on to provide charging to Nest.

J

[Mtnroads]

I'm scanning other posts because my question was never answered.

I just want to say that if I received this as an answer, it would be USELESS. A homeowner with a new thermostat needs to know what existing wires go into what Nest contacts. Knowing what controls a compressor or fan is useless.

[klamont9]

I ended up having a HVAC guy come out.  Turns out I didn’t need the Black - BK wire.  Now it works perfectly.   When I put BK to OB it would only cool.  

[jb76]

Hi - good to hear you and the HVAC tech. were able to identify the correct wiring to control your system. Typically this is done at the time a new/existing system is setup by a tech. that knows what your HVAC system consists of and type. 

J

[EdmondB]

Hi everyone, 

@klamont9, thanks for keeping us in the loop, and I'm happy to hear that this has been sorted out. BK wire is a dehumidification wire, and usually we advise our customers to talk to a Nest technician about setting it up with the 3rd generation Nest thermostat. If you need any help, let us know.

Cheers,
 Edmond