I just got a Honeywell RTH6500 thermostat and I don't think my existing boiler has a spot to hook up a C wire or to get me the 24v I need. Can anyone tell me if I can grab that voltage off of something here? enter image description hereenter image description hereenter image description here

If not, I want to use a separate 110VAC to 24VAC transformer to provide it.

  • It looks like those are pump relays. The 24 volts coming in to them is not going to be on all the time. Only when the pump is activated by the controller. You might be better off with a separate 24v transformer. – ArchonOSX Feb 11 '17 at 8:08
  • These appear to be pump relays which have an integral transformer. They sometimes don't expose the C wire and only give you the two wires that go to a passive thermostat. – Harper Feb 11 '17 at 16:44

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