I have a Goodman gmpn080-4 furnace and am installing a Skuttle 190-1 humidifier. Where do I wire the two wires from the humidistat to the furnace? I see a 24v HUM screw on the board, but not sure where to place the other wire.

  • Some pictures of what you're talking about would help your question – Machavity Jan 28 '18 at 18:20

Connecting one wire to HUM and the other to ground worked for us. I believe this is the solution for this furnace, as 'C' (Common) is usually recommended, but this model does not have a connection for that.


The other wire goes to what is called 'common', 'c' for short.

  • Thanks — this is the common advice found on the internet, and may help other searchers, but on my system there is no 'common' or 'c'. As we we're testing a few options we discovered that grounding the other wire appears to have been there solution. I suppose this is only applicable on units that include both the 24v HUM connection and no 'c' connection. – Aaron Silber Jan 28 '18 at 19:37

Couldn't you just check furnace wiring schematics for "C" common port? Just plug other wire (other than HUM to C area. Right?

Does a common "C" matter to voltage? Such as 24 volt to 24 volt common. Thx

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