topic Re: Is C wire needed? in Nest Thermostats

Is C wire needed?

MrTee1063 — Sat, 22 Jan 2022 12:06:12 GMT

Installed my Nest 3rd Gen. thermostat a week ago. It's a two-wire heat-only system. It's working fine but I've read that over time my battery is going to run down because there is no C wire. Can I tell by the battery voltage or the power level in Mw if this is happening?

Re: Is C wire needed?

Houptee — Sat, 22 Jan 2022 19:19:31 GMT

It could cause problems depends on the heating system do you have a boiler with zone valves?

It steals power without the C wire and can make some heating system valves start to chatter when it draws power away.

Best thing to do is always connect a C wire just run a new thermostat cable with 5 conductors minimum so in future you have extra if new system is installed.

Re: Is C wire needed?

MelbaDT — Sat, 29 Jan 2022 08:22:05 GMT

Hey folks,

Thanks for your answer and for your recommendation, Houptee.

@MrTee1063, it is always best to have a C wire as it will provide constant power to your thermostat. Take a look at this link to learn more about the C wire: https://bit.ly/3nIztHl

Best,

Melba