I’m adding steam humidifiers to our two HVAC units, they currently run on 110v but will double the output on 220v which we need. I’ve pulled 8 gauge wire to the panel box and will terminate in a junction box, split and run 10 gauge to each unit (short runs, about 20ft each). Max amperage is 17A for each unit.

For the double breaker I have an older 30amp double which fits (electrician removed it to install 40s for elevator); I’m assuming that means it has 30A on each leg, and therefore this breaker will work and my wiring is sufficient. Yes? Thanks for any help or comments.

  • Are these continuous loads? Nov 15 at 2:40
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    I think we're going to need planned wiring diagram, nameplates, instuructions etc. You seem to be under the impression that you can throw any number of loads on a breaker as long as breaker > total loads, and it's not like that. Nov 15 at 3:16

1 Answer 1


For 240, both phases conduct all the amps, since they're in series with the load. So, no, two 17A 240V loads will not fit into two 30A breakers, since 34A won't fit into either one.

  • Thank you keshlam for a helpful answer. I appreciate it. (I had bought a 40a double that afternoon but found the 30a double when rooting through the parts drawer. Guess I’ll use the new one.
    – Miffedone
    Nov 15 at 17:15

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