Thermostat wiring compatibility

[PSF57]

The wiring on my old thermostat has a slot labeled (O/B)W with an orange wire attached. This is not an option on the screen online to check compatibility with "pick your wires."

https://store.google.com/intl/en_us/widget/compatibility/thermostat/

I read there:

"Some thermostats have 2 labels on each connector. To see which label you should use, check Nest Help."

Clicking on that link, I do not find a clear answer, so I can not use the compatibility checker.

Connected wires are R, with a jumper to Rc, (O/B)W, Y, G, C

Again, the (O/B)W wire is orange; there is a white wire taped off, not connected to anything.

Which Nest thermostats will work for us? Thanks!

[HVAC]

Sounds like you have a heat pump system. That orange wire would go onto nest O/B slot & configure your system for heat pump forced air & then choose option O for now under O/B set up. You might need to switch it to B later when you test your system and you get cool instead of heat or heat instead of cool. Hope that helps. Good luck. 

[Jenelyn_O]

Hi folks,

Thanks for reaching out. The O/B terminal is for a reversing valve and the W is for heating. If ever you have a heat pump system, the orange wire will be responsible for reversing the valve from cooling to heating. Even if you have a heat pump or a conventional system, it would be compatible with the Nest Thermostats. 

You can follow this guide for more information: the Nest Thermostats don't use any jumper wires.

• Y/Y1 - Cooling
• G - Fan
• C - Common 
• O/B / *OB - Heat pump
• R/RC/RH - Power

I appreciate your help, @HVAC.

Best,

Jenelyn

[PSF57]

Thanks for the answers thus far. My confusion remains, however, what to do with the one wire slot labeled “(O/B)/W”. The Nest guide has these separated.

[HVAC]

Just use the orange wire to go to o/b slot

no need to connect anything to W  & configure your nest to heat pump forced air & choose O option for now.  Good luck 

[Jenelyn_O]

Hi PSF57,

I'm sorry for the confusion. Most of the heat pump systems don't have a separate wire for their heating (W) and cooling (Y), as the OB wire will serve as your reversing valve. 

If you have a conventional system, your orange wire will go to the W terminal. However, if you have a heat pump system, you'll need to insert your orange wire to the OB terminal to function as your reversing valve. 

There's another way to identify what type of system you have. Could you please provide your system make and model? 

I appreciate the input, @HVAC.

Regards,

Jenelyn