Need additional wiring help for nest thermostat, please

[ctoles]

I am having trouble figuring out where to connect the blue wire and the orange wire from my thermostat to the new Nest thermostat.   The unit is a heat pump with both heat and cooling,  Does the Blue wire go to the Nest C input and the Orange wire go to the Nest OB* input?  photos below of current thermostat wiring.  Thank you.

existing thermostat wiring

[Irishjedi]

The blue is your Common wire. Put that in C on your thermostat. That will give constant power to the thermo. The orange looks to go into the OB.

[ctoles]

Thanks for your quick response.  I think I should have provided some additional information when i asked for wiring help, I want to make sure I wire the thermostat correctly. I have 2 heating/cooling zones in the house, one for upstairs and another for downstairs.  The upstairs unit is a combo heat/cool/emerg heat heat pump unit with a dedicated air handler for this unit.  The downstairs system is a gas furnace with an associated cool only heat pump unit and the downstairs has its own dedicated air handler.  I am only wiring the nest thermostat for the upstairs heat pump.  Considering this additional information, do I still not need the orange wire? It was connected to the 0 terminal with the old thermostat.

[Irishjedi]

I only have a heat too and I didn't use the orange. I only used the red, white, and blue.  Hope this helps.

[ctoles]

The "heat pump" that I am wiring the nest thermo for provides cooling and heat. Still not sure if I am supposed to wire the orange to the 0B* slot. Should I try without orange first and see if all works ok, or should I go ahead run the orange to the 0B* ?  Thanks for any insight anyone can provide.

[Markjosephp · Accepted solution]

Hi folks,

Chiming in. I'd be happy to take a look into this for you.

I appreciate your help, @Irishjedi.

@ctoles, thanks for posting and letting us know the details of your HVAC system. Based on the wiring diagram from your thermostat, it appears that you have a heat pump type.

You can follow the same wire set up to the Nest thermostat with C (blue), R (red), O/B (orange), W (white), G (green), and Y (yellow). But if you have a Nest Learning Thermostat, move the white wire to the W2/Aux terminal.

Have a look at this article and let us know if you need more help.

Best regards,

Mark

[ctoles]

Thanks mark Joseph and irishjedi. I wired as outlined above with orange in OB* slot and blue in C slot snd all things seems to be working fine so far. Thanks for all the help.

[Markjosephp]

Hi ctoles,

Awesome! I'm glad to hear that it's working with the wire set up.

It looks like we have come to a solution so I'm going to be locking this thread in 24 hours unless you have additional questions or concerns.

Best regards,

Mark