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Nest thermostat wiring

otilioster
Community Member

My current system has both b and o wires, the nest thermostat has the o and b in one slot, how should I proceed? 

1 Recommended Answer

CoolingWizard
Platinum Product Expert
Platinum Product Expert

Just put the wire on B on the Nest C and the wire on O to the Nest O/B. 
Your wires will be Rc, G, Y1, O/B and perhaps AUX/W2. Can you upload a picture of your current thermostat showing the connected wire.

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.

View Recommended Answer in original post

4 REPLIES 4

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@otilioster , when you have a B terminal and an O terminal being used, you have a heat pump and the B terminal is used as power Common.  This is very true when the thermostat does not have a C terminal.  

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.

Thank you! So how would I wire it to the nest thermostat in this situation? Do I leave one of the wires disconnected?

CoolingWizard
Platinum Product Expert
Platinum Product Expert

Just put the wire on B on the Nest C and the wire on O to the Nest O/B. 
Your wires will be Rc, G, Y1, O/B and perhaps AUX/W2. Can you upload a picture of your current thermostat showing the connected wire.

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.