-1

I have a problem similar to the one in this question. My R wire from the thermostat to the G terminal on boiler and the W wire from the thermostat to the Y terminal on the boiler. The picture is a bit confusing since the red and white from thermostat were connected to 2 black wires.

13

1 Answer 1

0

You'll need to run a 4 wire thermostat cable

The issue with your proposals so far is that unlike many setups, your boiler (and some other Weil-McLain boilers as well) puts various safety controls ahead of the intended thermostat connection point in a steam configuration (see page 8 of the control supplement), so the wire that's typically connected to R isn't actually constant power. To avoid thermostat derangement in the case of a safety cutout or worse yet, bypassing a critical safety control (such as your all-important low-water cutoff!!!), you'll need to pull a 4-wire cable instead of your existing 3-wire cable, then wire it as follows:

  • Nest Rc to boiler R
  • Nest C to boiler C
  • Nest Rh to boiler G
  • and Nest W to boiler Y

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.