topic Re: Is Nest REALLY ok without the 'c' wire? Honest answers! in Nest Thermostats

Is Nest REALLY ok without the 'c' wire? Honest answers!

Plans4Nigel — Wed, 23 Nov 2022 04:18:53 GMT

We have an old forced air gas furnace. Lennox from the 90s. Heat only - no AC. Current thermostat doesn't have a 'c' wire. There are extra unused wires in the wall - but I'll be damned if I know where they go because they don't seem to terminate at the furnace. I opened up the access panels last night. Definitely no easily identifiable control board. A bunch of zig zaging wire clusters attached to different things in the guts of the furnace.

Going through the compatibility process with a Google agent - they said its fine to run the Nest learning 3rd gen without the 'c' wire. Which I learned later is possible due to the power stealing feature that recharges the onboard battery. However, there seems to be a lot of internet chatter around how unadvisable it is to run it without a 'c' wire. With that said, some say in a simple heat only set up, it works just fine without.

I'm a handy guy, but looking into the belly of that furnace makes me weary to dive in. If it were a simple control board like I've seen in the dozens of 'hook up your own c wire' videos - I'd be game. But my situation seems more suited for the professionals.

So now I'm faced with either rolling the dice and getting a Nest and trying to run without the 'c', paying a steep price to have in professionally installed with the 'c' (assuming that's even possible with my aging furnace), or just foregoing a smart thermostat for the time being.

If any of you have thoughts, suggestions or positive experiences with a 'c'-less Nest set up - please share!

Re: Is Nest REALLY ok without the 'c' wire? Honest answers!

Markjosephp — Tue, 29 Nov 2022 22:26:00 GMT

Hello Plans4Nigel,

Depending on the usage, the power capability and age of a unit will determine if C wire is needed. In most cases, Nest Learning Thermostats or Nest Thermostat E can charge their built-in battery using the heating and/or cooling wires. But there are situations where they may need to connect the Nest Power Connector or a common or C wire to consistently deliver power to the thermostat. However, the Nest Thermostat (2020) often requires a C wire to work.

Here are some references to help you learn about the Nest Power Connector and a C wire:

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

Thanks,

Mark

Re: Is Nest REALLY ok without the 'c' wire? Honest answers!

Markjosephp — Fri, 02 Dec 2022 22:59:32 GMT

Hi there,

I wanted to see if you still needed help. Please let us know if you have any other questions or concerns.

Best,

Mark

Re: Is Nest REALLY ok without the 'c' wire? Honest answers!

Markjosephp — Sun, 04 Dec 2022 21:59:20 GMT

Hi Plans4Nigel,

I'm checking in to make sure that you've seen my response. Please let us know if you have any additional questions or concerns before we lock this thread in 24 hours.

Thanks,
Mark