Nest Thermostat Radiant Baseboard Heat with 3 wires

[BeoRob1]

I have a radiant baseboard heating system with White Rodgers 1311 zone valves for control. They have 3 wires used on the old thermostat, R, W, O/B. The O/B is the issue. It normally closes the zone valve when the room(s) reaches temperature. I have installed the Nest Power Connector to provide a “C” wire. When I configure the O/B in the app, it thinks it’s a second stage heat, which is not what I need. I need something in the thermostat to close the zone valve. 

[humbertogarcia]

Hi  BeoRob1,

Thanks a lot for posting in the community! I'd be absolutely glad to dive into why your Nest Power Connector isn't working as a zone valve closing for your White Rodgers 1311.

To get a really clear picture of your unique installation, I'll need a little more information. No worries, we'll definitely get to the bottom of this together! Could you tell me:

• What's the specific model of your thermostat? You can check How to tell which Nest thermostat you have
• Has the Nest Power Connector not worked as you expected since it was initially installed? You can check Nest Power Connector
• When did you install the thermostat?
• Did you check how the old thermostat was wired to that White Rodgers 1311 zone valve?

Once I have these details, I'll be happy to investigate why the Nest Power Connector seems to think the connection is for a second stage of heat instead of providing the expected function. Looking forward to hearing from you!

Regards,

Humberto

[BeoRob1]

Humberto, Thanks for your reply. I have, as I wrote in the title of this post, the Nest Thermostat. Not the “E”, not any “Gen” or any “Learning”. Just the Nest Thermostat. That’s it.

I have not fully installed it until I was sure it would work. I had it and the Nest Power Connector connected to the appropriate wires, just not attached to the wall.

The “issue” has not started since the install has not been completed based on the fact that it did not operate the boiler to begin with. What I have read with other smart thermostats is I need the ability to reverse the zone valve with the 3rd wire (O/B).

[humbertogarcia]

Hi BeoRob1,

Thank you for enforcing the description of your Nest Thermostat (2020) type and for the information provided about the test wiring. I find that the situation is a common challenge with radiant heat and those specific zone valves.

It sounds like you've correctly identified that the "O/B" wire on your old thermostat is meant to actively close your White Rodgers 1311 zone valve.

Let's consider the following: your Nest Thermostat (2020) uses its O/B terminal for very specific purposes, primarily for heat pumps (reversing valves) or sometimes for a second stage of heating or cooling.

Based on information in the help articles Nest termostat star terminal and Nest thermostat compatibility, the Nest Thermostat (2020) isn't designed to directly control a zone valve's closing signal via that O/B terminal. It doesn't have a setting to tell it, "This O/B wire means close the valve when the room is warm." That's why it's thinking it's a second stage of heat.

Because of this, directly connecting your zone valve's closing wire to the Nest Thermostat (2020)'s O/B terminal won't give you the control you need. You'd typically need to use an external relay to bridge that gap, but that adds complexity and usually requires professional help.

I know this might not be the easy answer you were hoping for, but I wanted to be upfront about the compatibility.

Regards,

Humberto

[BeoRob1]

Humberto,

Thank you for your honest reply. I was hoping to use the Nest Thermostats, but alas will not be able to. I truly appreciate your time.

[humbertogarcia]

Hi BeoRob1,

It's understandable that you're disappointed about not being able to use the Nest Thermostat for your specific setup, especially after hoping it would be a fit. I truly appreciate your understanding and your kind words.

Certain specialized systems like yours require a very particular kind of control that even the most versatile smart devices aren't natively designed for. It's a shame when this happens. I'm glad we could check it out together.

Please don't hesitate to reach out if you have any more questions about other smart home devices or need assistance with anything else.

Regards,

Humberto