Reply Wed 30 Oct, 2013 10:54 am
30 amp double pole breaker with #10 wiring going to a wall switch by the water heater. I have 120 volt on the red wire coming into the water heater (to ground) and 120 volt on the black wire to ground. I have been told that this does not necessarily mean that I have 240 to the water heater, but the person was unable to tell me why. Can you?
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Reply Wed 30 Oct, 2013 01:06 pm
If they were in phase Dad the voltage difference is zero but then of course your heater wouldn't work
Reply Wed 30 Oct, 2013 01:41 pm
Well, the heater didn't work, that is what started all of this. What the problem ended up being is that one side of the double pole breaker went bad, but it did not trip the breaker. My confusion was/is that how am I getting 120 volts to each side, but not 240 to the element? In other words when I test the red and black separately, I was getting 120 volts each, but when I tested them together, I was not getting 240 volts.
Reply Wed 30 Oct, 2013 04:10 pm
Dad I'm just beginning to vaguely fathom your predicament. If one side of the breaker is open but the dryer still connected of course you'd see the same 120 v on both terminals. But you should consider the possibility it isn't really a malfunction. On some "modern" breakers it won't come back on unless you first switch it off then back on but very vigorously

I know, unbelievable, but try it. Easier than running out to buy new breaker that might act the same way
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Reply Wed 30 Oct, 2013 08:33 pm
You read 120V to ground on both wires because the phase leg that opened is still connected through the heater element to the phase leg that is still closed with the 120V. If you opened the switch at the heater so there was no load connected, you would only read 12oV to ground on the one energized phase and not the other.
Reply Thu 31 Oct, 2013 12:06 pm
Thanks Bah, exactly what I was trying to convey but through less elegant and direct language
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