I recently re-wired my water heater from 120v to 240v. I'm not sure why it was wired with 120v to begin with, but it was not providing enough volume of hot water. I looked up basic thermostat wiring diagram, and it appeared as if the thermostat was wired wrong, so I moved a wire.

Can anyone confirm that the wiring is correct? I've uploaded the before and after shots of the wiring change.

The third picture shows a jumper that I can't seem to see in any wiring diagrams I look at.


Before (was operating at 120v this way)


After (now supplied with 240v)

Should this jumper be left or removed:

Should this jumper be left in place or removed

Click for full size image

1 Answer 1


I just did a search for John Woods thermostat wiring and found the John Wood website.

Then I used it, and your pictures to create the modified picture below.

It looks to me like you have it wired right. Also, it looks like the original wiring was done so that both the upper and lower heating elements would be on at the same time. With it wired the way you have it now, the upper element should go off when it reaches its set temperature, and simultaneously turn on the lower element. I would check this with a voltmeter if I were you.

I AM NOT AN ELECTRICIAN: JUST A DO-IT-YOURSELFER OF ABOUT 50 YEARS. So, you might want to wait for a real electrician to respond.

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Click for larger view

  • Good edit Tester101. I wish I had thought of that.
    – getterdun
    Nov 22, 2013 at 18:23

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