Nest Thermostat - no C wire, baseboard heat only

[spq_easy]

My house is a little older and does not have any fancy / central HVAC. I have three zones for baseboard forced hot water heat from an oil furnace. I installed two nest thermostats for the two main zones when we bought the house about 7 years ago and they have worked great. There is a small part of the basement that is finished and is on a third zone, but it had been shut off for years. After recently completing some repairs the heat finally works in that room again and the zone is back on!

So I bought the new Nest thermostat. I opted not to get a learning one for this zone as it doesn't need to make any fancy adaptations. Just a simple schedule. When I went to install it I discovered it uses batteries (NBD) and seems to require a 'C' wire? The system only has red and white, and my other Nest thermostats have never had an issue. I've checked the control panel on the furnace and it does not have a 'C' to run a wire from or connect the google power adapter.

Does this thermostat really require the third wire to only control the heat?

Do the current learning thermostats have the same issue?

It looks like an option is to buy and install a separate 24 VAC/20 VA transformer to hook into the system, but since I haven't had an issue with my other Next thermostats I'm wondering if that is really necessary?

file:///C:/Users/squinlan/Downloads/Nest_Power_Connector_Pro_Installation_Guide.pdf page 11

Thanks!

[spq_easy]

Sorry about the bad link, and I can't seem to edit my post. Here's the actual link: https://storage.googleapis.com/support-kms-prod/k5rpNEXV1F0aVYhr8jN1L2GAxhcAPDXhk39r

[GabrielaG]

Hi spq_easy,

Thanks for reaching out to the community. I'm sorry to hear that your Nest Thermostat is not working as expected and is needing a C wire to make the system work. I'm happy to help you right now.

Nest thermostats are designed to use very little power, and in many cases they can use your system’s heating and cooling wires to get enough consistent power. But sometimes, you may need to connect a common wire (C wire) or power accessory, like the Nest Power Connector, to make your system compatible. A C wire does not regulate heating or cooling, in contrast to other wires that are attached to your thermostat. It just gives your thermostat constant power.

You can refer to these articles to Learn about the common or C wire or the Nest Power Connector.

Feel free to keep us posted if you have more questions.

Regards,

Gabriela