I have two thermostats running two different fans wired up like this:

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I'd like to replace the 2nd thermostat (on the right, in box #2) with a switch. I have done this and have the ability to turn Fan #2 always on, regardless of thermostat #1. I'd like the opposite, and am not sure how to wire it.

Desired operation:

  • Thermostat #1 controls both Fan #1 and Fan #2 at the same time.
  • If new switch (replacing Thermostat #2) is off, Fan #2 does not run.

Just replace A with B. In Box#1 disconnect the live wire to the switch for Fan#2, from the 120V source and connect it to the Fan#1 terminal.

If these "high voltage" thermostats are actually carrying the load current, not using a relay, make sure Thermostat 1 can handle the current for both fans.. Look at the labelling or documentation for the thermostat and for the fans to figure that out.

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