I have a 2-stage furnace and I want to connect the 24VAC from the humidifier to the thermostat connections on the control board. Since the control board has W1 and W2 connectors, which one should I use in conjunction with the C so the humidifier operates when the blower runs?

Electrical wiring schematic

  • Can you post the wiring diagram for your furnace, as well as photos of the control board? Aug 27 '18 at 22:51
  • Wiring schematic posted. I can send a PDF version (couldn't figure how to post) if needed. Aug 28 '18 at 18:07
  • Can you post a link to a PDF version of the manual -- or just the make/model number for that matter -- in a comment? Aug 28 '18 at 22:49
  • Model # FG7TA Finding the manual online is a challenge. Aug 28 '18 at 23:42
  • Make is Westinghouse Aug 28 '18 at 23:43

W1 should work

If you want the humidifier running whenever the heat's running, then using the W1 and C terminals on the thermostat connection should indeed work.

...but, I'd make sure there's a humidistat on this

However, I would make sure there's a humidistat controlling the humidifier (it can simply be in series between W1 and the humidifier, provided it's an open-on-rise/close-on-fall type) as well, as too much humidity is a rather effective way to slow-kill a house.

  • Thank You - and, yes, there is a humidistat controlling the process. Sep 1 '18 at 13:50
  • 1
    @RichardBenz -- we say "thank you" around here by upvoting and accepting folks' answers :) Sep 1 '18 at 13:53

The fact that you have a 2 stage furnace is less important in regards to your humidifier then if you have a 2 stage thermostat. The W1 are W2 terminals on the furnace are input only. They wait for a 24v signal. So if you have a single stage thermostat connected to W1 the furnace will kick in to 2nd stage after a pre-determined amount of time. Connecting to W1 would apply here. With a 2 stage thermostat the W1 contact is usually maintained during a call for second stage heat by the thermostat, so connecting to W1 still applies here. Sometimes I've run into a 2 stage with only a W2 connection at the furnace. Making it an expensive single stage furnace. In that odd case connecting it to W2 is the appropriate action. Or you could just wire the transformer into the HUM terminal.

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