I have an A. O. Smith 40 gallon 4500W. Can I change the element to 3500W to run it on a double 20 with 12/2 wire?

  • As the answer says you can do it, it will take longer to heat up the water.
    – crip659
    May 28 at 9:54

1 Answer 1


I don't see any reason why not, depending on the length of your run.

I assume your run is in place, and you don't want to disturb it? Otherwise, I guess you'd just run #10 and keep the 4,500 watt element.

If your run is too long to pass 20 amps over #12, then it won't work. Consult length-of-run versus ampacity charts to be sure. But your 3,500 watt element should pull just 16 amps at 220 volts, so I imagine #12 is going to work for reasonable lengths.

  • Its only like 15 ft run
    – Mike
    May 28 at 3:28
  • Yes wire already run
    – Mike
    May 28 at 3:29
  • 1
    It is 240 not 220 how do i find lenth of run vrs amp
    – Mike
    May 28 at 3:33
  • 1
    Yeah, you have to be going at least 180' before voltage drop is going to matter on a 240V circuit. May 28 at 6:36

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