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Old 02-19-2011, 02:54 PM   #1
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Bad breaker?


Hi;
My brother is having trouble with a breaker tripping when the vacuum is run.
His wife said it trips out occasionally when the vacuum is first switched on.

I went over there today, and have the following info:

The breaker in question is a Square D single pole tandem 15A.

I measured the current on the branch with my clamp-on ammeter, and found almost nothing until the vacuum is turned on.
The vacuum draws 12A, but the starting surge is at least 25A.
Unfortunately, we could not reproduce the problem while I was there, so I did the easiest thing I could think of; swap the wires from the two tandem breakers. If the problem persists, then we need to look at rewiring and upgrading to 20A. If not, then the breaker is probably faulty.

There is no more room left in the panel for another breaker, so we must stick with the tandem ones.

I have heard of instances where breakers become "weak" and trip out prematurely, especially on short surges like this.

Is there possibly a problem with tandem breakers in this situation? I wouldn't think so, since they are still rated at 15A, but I don't have all that much experience with breaker failures. For the most part, I find breakers to be extremely reliable devices.

Thanks for your advice

FW

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Old 02-19-2011, 03:47 PM   #2
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Bad breaker?


Is it possible that there were other devices on that circuit that were turned on with the vacuum and made it trip? Perhaps there was a space heater, iron, or other hefty appliance in another room that was operating while she tried to vacuum? If you can confirm that the vacuum alone was responsible for the breaker tripping, then the breaker is not functioning normally and should be replaced. A new 15A tandem breaker should be fine.

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Old 02-19-2011, 06:57 PM   #3
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Bad breaker?


vaccumes use a lot of power, typically no breaker should be loaded to over 80 %. 12 amps continuous on a 15 amp breaker is ok however the surge is probrably what is tripping your breaker. I would advise to run new wire and upgrade to 20 amp breaker.
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Old 02-19-2011, 07:34 PM   #4
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Bad breaker?


Yes, it is possible that there was something running at the time that neither my brother or his wife is aware of. If that is the case, then the breaker should continue to trip occasionally. Although my brother has a list of "everything" on every branch, I know by experience that it is possible to have swapped something from one receptacle to another after creating the list.

jadbad2004, I agree with you. The correct solution is to rewire the branch(es) and upgrade all wiring to #12 and the breaker to 20A.
I think that eventually that is what we or an electrician are going to have to do.
We would have to do quite a bit of work though, and probably not only on the two circuits that are on the tandem breakers. I have a feeling that there are things an inspector would not like, and we would have to fix everything before our work would pass inspection. I'm not complaining, but I would want it to be done right, and get the proper permit and inspection that are required.

FW
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Old 02-19-2011, 08:01 PM   #5
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Bad breaker?


There is no need to use a 20A circuit for a 12A vacuum. Circuit breakers are designed to carry their rated current indefinitely without tripping (though the electrical code requires that they not be loaded to more than 80% of their rating for continuous loads). A 12A load on a 15A breaker is perfectly acceptable, even as a continuous load. The starting surge should not trip it, either.
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Old 02-19-2011, 08:13 PM   #6
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Bad breaker?


Quote:
Originally Posted by mpoulton View Post
There is no need to use a 20A circuit for a 12A vacuum. Circuit breakers are designed to carry their rated current indefinitely without tripping (though the electrical code requires that they not be loaded to more than 80% of their rating for continuous loads). A 12A load on a 15A breaker is perfectly acceptable, even as a continuous load. The starting surge should not trip it, either.
that is assuming nothing else is on that cb
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Old 02-19-2011, 10:41 PM   #7
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Bad breaker?


A 12 amp fla vacuum on a 15 amp rated branch circuit should be just fine assuming your not vacuuming your neighbors living room with long extension cord and voltage drop is killing you. 80% load on a breaker is a common misconception by many people as mpoulton pointed out. Literally thousands of 12 amp vacuums operate on 15 amp general purpose branch circuits.

There may be something plugged into that branch circuit that cycles on and off like a space heater. It could be a 'weak breaker' but that is generally a long shot .. but certainly not impossible. There are in fact several reasons the breaker may be tripping .. further information and testing is required.

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