I recently purchased a new Thermostat with Wi-Fi capabilites for use in one zone of a two zone baseboard hot water heating system.
I pulled the existing thermostat (stat) to look at the wiring and only two wires were connected to the old stat, namely a red and white wire. However, there was a thrird green wire that was wrapped around the existing wiring that was unused on both the stat end and also at the boiler.
I believe that the unused green wire can be used as a c wire in the exisiting setup. I located the transformer and there looks to be both a terminal with an R next to it and one with a C next to it.
I've added a couple pictures of the wiring at the boiler. It seems each white wire runs to the respective zone valves (zone 1 and zone 2) and then are joined together to return to the R terminal on the transformer. The red wire from the stat is connected to the C terminal on the transformer (2 red wires - one each respective zone/stat).
Is the correct place to connect the green wire at the C terminal of the transformer where the two red wires also connect?