Wiring smart thermostat

[alex2929]

We do not have central air in our house. It is heated with hot water base board heat from a boiler. We have a traditional old fashioned honeywell thermostat currently n I am trying to wire up a Honeywell RTH9585WF thermostat. We have two wires going to our thermostat currently. Red and white. We do not have this 3rd “c” wire that the directions mention. They act like with our system it can be wired without by I’m confused exactly how. Can anyone help?

 

[Bert_]

C is just common. The digital stat wants it otherwise it just runs on the battery. With a c wire it gets power from the boiler. It's not needed if you put batteries in the stat. If you don't have the wire you just don't hook it up

 

[MikeF2316]

I have one of those thermostats. I have a C wire, and they are necessary on this thermostat as there is no battery. It's a WIFI stat, I guess they use too much power for any kind of battery life.

Your system needs to have 24 volt (AC) controls for this to work, and ideally you're going to need a 3rd wire. However this "wire saver" may work for you: THP9045A1098

 

[jbwilkins]

... It's a WIFI stat, I guess they use too much power for any kind of battery life.......

WiFi can be 'battery hungry'........

 

[ovilla]

You can also just use one of these kits to add a C wire to your thermostat.

24Volt Doorbell Transformer, C - Wire Adapter Thermostat, Compatible with Nest,Honeywell,and Ecobee Smart WiFi Thermostat, Nest Hello Ring Video Doorbell https://www.amazon.com/dp/B07RXL53K5/?tag=atomicindus08-20