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Old 08-31-2009, 01:19 PM   #1
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Oversized Breaker


Will be moving in to a new home in about a month, and just had an inspection done. One of the items noted was that there is an oversized breaker (20amp) in the main distribution panel, I believe that the wiring is still the standard 15amp type.

As a safety issue the inspector advised that we should replace it with a 15amp. I am wondering if this is something that an electrician should do, or if this is something that I can do myself.

I have only done minor electrical work in the past (ie replacing dimmers and outlets).


Last edited by djdragan; 08-31-2009 at 01:31 PM.
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Old 08-31-2009, 01:24 PM   #2
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Oversized Breaker


What Mfg breaker panel?
Is there any shut off ahead of the panel so that everything in the panel is dead?
A breaker is (usually) not that hard to change out

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Old 08-31-2009, 01:30 PM   #3
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Oversized Breaker


Hmmm, I don't know the manufacturer, and we likely won't have access to the house again until possession on the 25th of Sept. The inspectors report notes that the panel has a "Main Service Rating" of 100amps and "Panel Rating" 125amps.

I don't recall there being any other shutoff before the panel, only the main power shutoff on the panel itself.
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Old 08-31-2009, 01:31 PM   #4
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Oversized Breaker


That breaker may be there to hide some other problem. If it is #14 wire on a 20A breaker the wire insulation is probably crispy by now.

Some/most/few inspectors don't want to kill the deal so they may only tell you about very dangerous stuff for which they are likely to be sued.

Last edited by Yoyizit; 08-31-2009 at 01:36 PM.
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Old 08-31-2009, 01:35 PM   #5
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Problem? I hope not!

The inspector said it was probably put in as they were running some type of motor from that outlet. I do remember that there was a treadmill in the basement near that outlet that has the 20amp breaker. The house was empty when the inspection was done, so we couldn't confirm if that was the reason.
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Old 08-31-2009, 01:46 PM   #6
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Oversized Breaker


Quote:
Originally Posted by djdragan View Post
I do remember that there was a treadmill in the basement near that outlet that has the 20amp breaker.
Bingo! We have a winner!

#14 wire is .064" dia. [1/16th of an inch], #12 is .081" dia. [5/64ths]. You guys on the metric system?

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Old 08-31-2009, 01:50 PM   #7
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Originally Posted by Yoyizit View Post
Bingo! We have a winner!

#14 wire is .064" dia. [1/16th of an inch], #12 is .081" dia. [5/64ths].

So do you think there was damage done to the wiring by the previous owner just installing a 20amp breaker and not actually changing the wiring? How could I check this?

The inspector said that if were going to use that outlet to run a motor, then it wasn't necessary to change the breaker, but that it should be changed for everyday usage.
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Old 08-31-2009, 02:02 PM   #8
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Oversized Breaker


Quote:
Originally Posted by djdragan View Post
So do you think there was damage done to the wiring by the previous owner just installing a 20amp breaker and not actually changing the wiring? How could I check this?

The inspector said that if were going to use that outlet to run a motor, then it wasn't necessary to change the breaker, but that it should be changed for everyday usage.
I doubt the wire was damaged, but I'd inspect the insulation where it connects to the breaker and where it connects to the outlets.

It needs to be changed to 15A if it is 14awg romex wire.


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Old 08-31-2009, 02:53 PM   #9
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Quote:
Originally Posted by djdragan View Post
So do you think there was damage done to the wiring by the previous owner just installing a 20amp breaker and not actually changing the wiring?
1
How could I check this?
2

The inspector said that if were going to use that outlet to run a motor, then it wasn't necessary to change the breaker, but that it should be changed for everyday usage.
3
1
I think the life of the insulation has been shortened.
2
Dunno'. A megger?
3
Bless his heart. Having two degrees in elec. eng., IMHO and putting it politely, I think that is nonsense.

The chance of a house fire for any reason within one year is about 1/1000, about the same chance as me dying within three weeks.
I'm not an actuary but you could ask an insurance company what they would charge each year to insure this house, and then what they would charge each year to insure this house knowing that there is at least one wire in it with 'crispy' insulation.

In the link below, event B is having a wire with "crispy" insulation, event A is the house fire.
See An example in
http://en.wikipedia.org/wiki/Conditional_probability

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Old 08-31-2009, 03:01 PM   #10
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Oversized Breaker


If the load on the wire did not exceed 15a then I'd say you are OK
Possibly the treadmill starting power caused the 15a to trip
So they installed a 20a

Is this run dedicated to just that outlet?
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Old 08-31-2009, 03:25 PM   #11
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[quote=Scuba_Dave;321866]If the load on the wire did not exceed 15a then I'd say you are OK
Possibly the treadmill starting power caused the 15a to trip
So they installed a 20a

Is this run dedicated to just that outlet?[/quote]

Yes I believe that this breaker runs only to the one outlet.

Also, pardon my ignorance, but what is a megger?

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Old 08-31-2009, 03:47 PM   #12
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http://www.google.com/search?client=...UTF-8&oe=UTF-8

I don't have one so I don't know how a Megger responds to insulation with cracks in it, or insulation that has had the moisture driven out of it.
This issue may be "down in the noise" for insurance companies, depending on how many houses are in this condition and still don't catch fire.
The NEC is conservative but 20A will give you almost twice the conductor heating as 15A will.

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Old 08-31-2009, 04:39 PM   #13
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Oversized Breaker


Once you get into your house, turn that circuit off and figure out what it does. It could feed a motor load that needs a little extra jam for startup, i doubt a treadmill would cause this.

If it goes to a speciality item(i.e. your AC) ask before changeing the breaker it may be bigger for a reason and yes it is possible to have smaller rated wire then what the breaker is rated for(#14 wire on a 20A breaker)

If it goes to a plug check to see what size of wire is used, if it is #14 you will have to switch the breaker to a 15A, if #12 wire is used you can either change the breaker or change the plugs on that circuit to the 20A tslot plugs.
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Old 08-31-2009, 09:22 PM   #14
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Oversized Breaker


It's true that a breaker can be oversized (within limits) for a motor circuit, but the only time a receptacle can be fed with a larger breaker is in the case of more than one 15 amp receptacle fed with a 20 amp circuit. One duplex is more than one receptacle.

For example, in no case can a 15 amp single receptacle ever be connected to a 20 amp breaker, but a 15 amp duplex can.

Another example; a 1HP motor operating at 115 volts can be connected with #14 or larger wire. The maximum breaker size is 40 amp. That's right; #14 wire connected to a 40 amp breaker is completely code compliant, provided the motor is hard-wired.

Please note; with few other exceptions, the only time it's permitted to oversize breakers is with motors, A/C units, and welders. With just about everything else, the breaker size must match the wire size, though the wire can be larger.

A megger is a test instrument that supplies a high voltage at low current for the purpose of determining the condition of the insulation of the conductors. In the case of the OP, all loads must be disconnected from the circuit, and 1000 volts would be applied to the circuit. 3 tests would be conducted, hot to neutral, hot to ground, and neutral to ground. If there were any fault in the insulation, the megger would show low resistance. If the insulation is good, the resistance reading would be very high.

The reason such a high voltage is used is because normal power would never get that high, so if it can stand 1000 volts, it can certainly stand 120 volts. If there is a fault, a megger produces such low current that there's no chance of a fire or explosion.

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Old 09-01-2009, 12:04 PM   #15
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Quote:
Originally Posted by micromind View Post
It's true that a breaker can be oversized (within limits) for a motor circuit, but the only time a receptacle can be fed with a larger breaker is in the case of more than one 15 amp receptacle fed with a 20 amp circuit. One duplex is more than one receptacle.

For example, in no case can a 15 amp single receptacle ever be connected to a 20 amp breaker, but a 15 amp duplex can.
So just to get this if the receptacle is a duplex (I'm almost certain that it is), then the wiring should be ok? I will check it when we get in the house.

I'm gussing the breaker should still be changed back to 15amp as well as the receptacle (if it is a 20amp).

Is the changing of the breaker something I should be attempting myself, or would it be better to have an electrician do it? I don't recall seeing a shutoff ahead of the panel as Scuba_Dave had asked, but I will chack when we get posession. Is it unsafe to attempt this without shutting of the power ahead of the panel itself?

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