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Old 01-12-2010, 05:56 PM   #1
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phantom breaker


We tried to replace a wall heater yesterday (240 volts on a 20 amp double breaker). It was supposed to be a very straight forward job but we ended up with an electrical problem with the wiring.

This is in common area of a condo complex. There are 7 meters in the basement. One breaker panel for common area. Then each unit has a panel inside the unit which we don't have convenient access to.

1. Initially: black to red at heater around 240.
2. Turn off breaker.
3. Black to ground 0. Red to ground 120.
4. OP attempted to replace with the hot red wire (mistake) and shorted wire to ground
5. Half a second spark. Red went to 0. No breaker flipped on common area panel.

Now the red is at 0. Breaker has 240 volts at the red and black coming out at the breaker on the panel. But that red did not turn off when we turned the breaker off while the black did!

One possibility is that the red comes out of one of the units and flipped some breaker in the unit adjacent to the heater. But then I have a black on one meter and a red on another! Is this possible?

What else could be the problem? We did not smell anything nor we saw any melted wires at either end where the red is visible. Could the red wire have melted somewhere in between the panel and the heater? Can a half a second spark cause this?

Thanks much!

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Old 01-12-2010, 06:54 PM   #2
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One possibility is that the red comes out of one of the units and flipped some breaker in the unit adjacent to the heater. But then I have a black on one meter and a red on another! Is this possible?
absolutely and that is exactly what it sounds like but, before you start checking all the unit panels, try manually turning off and back on (reset) each breaker in the common area panel and check for power at the heater. I have had breakers that tripped that did not look like they were tripped. If somebody grabbed the other leg from a breaker other than the 2 pole, you could still experience what you are.


so, is this a problem if one of the units is feeding the heater? absolutely. They are paying for 1/2 the power to run the heater plus, legally, you have to have the power from one panel.

how can you have this? the service to the building is the service to the building. It all comes from the same transformer and very likely comes in on the same service feeder and splits in house to the various meters.

essentially all you have is a bunch of panels fed with the same power. If you take one leg from one panel and the opposing leg from another panel, the power knows no difference.

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What else could be the problem? We did not smell anything nor we saw any melted wires at either end where the red is visible. Could the red wire have melted somewhere in between the panel and the heater? Can a half a second spark cause this?
it wouldn't melt a wire this quick but if there was a bad joint somewhere in the circuit, it could have burned it to the point it won't carry any power anymore.

You might have to physically track the circtuit from one end to the other if this is the problem.

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Last edited by nap; 01-12-2010 at 06:56 PM.
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Old 01-13-2010, 06:00 PM   #3
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thanks for reply. It was a breaker that did not look flipped but was. Resetting all the breakers fixed it. I then found the breaker. It is an unlabeled single pole 20 amp breaker for the red and a double pole for the black. My guess is that the double pole is shared with one of the other heaters but did not bother to verify (most buildings have 3 double pole breakers - one for each heater). At least its not coming from another unit.
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Old 01-13-2010, 07:22 PM   #4
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You should put the heater on a single double pole breaker to prevent this kind of confusion in the future.
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Old 01-13-2010, 07:29 PM   #5
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Originally Posted by mihamih View Post
thanks for reply. It was a breaker that did not look flipped but was. Resetting all the breakers fixed it. I then found the breaker. It is an unlabeled single pole 20 amp breaker for the red and a double pole for the black. My guess is that the double pole is shared with one of the other heaters but did not bother to verify (most buildings have 3 double pole breakers - one for each heater). At least its not coming from another unit.
you do need to have the two conductors that feed the one unit on a common trip breaker
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Old 01-13-2010, 07:38 PM   #6
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Originally Posted by Gigs View Post
You should put the heater on a single double pole breaker to prevent this kind of confusion in the future.
Single double pole breaker sounds confusing. Separate double pole breaker would be more appropriate language, IMO.

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