C wire with Honeywell V8043F?

sameguy

We have a boiler with 3 zones of hydronic heating in our house. Wife wanted smart thermostats so I got some inexpensive Amazon Smart Thermostats. Ther require a C wire for constant power. There is an extra wire at each thermostat, but at the Honeywell V8043F where they are connected the third wire is not connected to anything. I have looked at a wiring diagram for the Honeywell V8043F and see there are 2 wires that go to the low voltage transformer. Can I connect the 3rd wire to one of those for constant power?

Robert O'Brien

TR terminal

sameguy

Thank you sir, very much appreciated!

EdTheHeaterMan

The C wire is not the only important wire to connect to the proper terminal on the new thermostat. You must connect the R wire to the proper terminal on the thermostat also. With a 2 wire setup there is no problem reversing the wires. When a Common is required then the R from the thermostat MUST be connected to the R on the transformer.


In this picture, to make things easier, I would use the unused white wire to connect W on the thermostat to the terminal you indicated as #4. Then I would use the Red wire to connect the R on the thermostat to the terminal you indicated as #3 (as it currently is). I would then connect the disconnected Black wire to C on the thermostat and #5 on the zone valve.

sameguy

Edward, thank you for the clarification.