Nest Learning Thermostat

[Midknight]

I have two questions.

I have an oil burner with central AC, and two zones upstairs and downstairs. If I set the downstairs to either heat or cool will the upstairs Nest Learning thermostat also switch automatically?

The second question is my system does not have a Heat Pump but the old downstairs thermostat had both a B and an O wire connected to it as well as the control board. It was not a smart thermostat and had a switch that I switched to either heat, cool, or off. The downstairs was Zone 1 and it determined whether the system was off or in heat or cool. The same upstairs Zone 2 thermometer did not have a B or O wire connected.

So I ask does the Nest Learning thermometer need either the B or O wire? 

Both thermostats are connected to a DuroDyne SMZ 2 control board.

Thanks in advance

[Markjosephp]

Hello Midknight,

I'm sorry for the delayed response. I definitely wanted to stop by and see how I could help.

For your first question, Nest thermostats are not designed to communicate with each other, but they will automatically set your target temperatures. Once the system is on and both have the same target temperature, they will both turn on.

Lastly, to make sure the correct wiring configuration to your other Nest thermostat. Could you check the make and model of your HVAC equipment? Also, please send us a clear picture of your previous thermostat wiring diagram. This is to check the type of system you have.

Looking forward for your response.

Thanks,

Mark

[Jhonleanmel]

Hey folks, 

Thanks again for helping here, @Markjosephp. 
@Midknight, I hope you've got the answer you're looking for. If you're still in need of any assistance, feel free to let us know. 

Best,
Mel

[Jhonleanmel]

Hi everyone,

Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let me know.

Thanks,
Mel

[Midknight]

I have one more question about your B/O terminals on the thermostat. What are their functions, in other words, which terminals are connected when in the heat or the cool mode? If B connects to R in the heat mode and O connects to W in the cool mode then a diagram I found on the Durzone website for the SMZ SW panel solves mine as well as other people's problems with older thermostats that have the separate B and O terminals. Here is the link: http://www.durodyne.com/durozone/SMZwithWIFI%20ThermostatwithB-OTerminals.pdf

[Markjosephp · Accepted solution]

Hi Midknight,

Thanks for sharing the picture. That helps!

Some Heat pump systems has O/B terminals. For the O configuration, the heat pump defaults to heating. So, when your thermostat is in cooling mode, the OB wire stays energized. For the B configuration, the heat pump defaults to cooling. So, when your thermostat is in heating mode, the OB wire stays energized. 

If you have separate O and B wires, the B wire is usually to the C terminal alone for common wire, and the O wire is for the heat pump.

Feel free to let us know if you have more questions in mind.

Best regards,

Mark

[Markjosephp]

Hello Midknight,

I know it has been a while but I wanted to ensure that everything is covered here. Still need help?

Best regards,

Mark

[EmersonB]

Hi everyone,

@Midknight we haven’t heard any updates from you. I’ll go ahead and lock this thread in 24 hours. If you're still in need of assistance, feel free to start a new thread and we'll be happy to help.

I appreciate your response, @mark and @mel.

Regards,
Emerson