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Would you call it a defect if you saw a 12 AWG wire on a 30 AMP breaker?

I guess most would.

How about a 40 AMP breaker?

How about a 50 Amp breaker?

Would you believe a 60 AMP breaker?

Yes these are all possible. And safe. And code compliant.

If you doubt this read Article 440 of The NEC.

 
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8 Comments on 12 AWG on a 30 AMP breaker?

APR
01
2007

Best thing to do is always read the manufacturers data plate on the A/C compressor before looking into the electrical panel.  That way you'll always know the breaker size required.  The nameplate will look something like this:

 

The Minimum Circuit Ampacity figure will indicate the wire gauge required, in the above it would require 10 gauge. It will also list the Maximum Overcurrent Protection device. This means that your panel breaker cannot be of a greater value than what's listed. This is regardless of the ampacity of the branch circuit.

This is a great topic Mike and one that can be very misleading since sizing circuits for electric moters is a bit different than residential branch circuits.  Perhaps this link will explain the sizing in more detail for anyone wanting to know a bit more.
5:32pm • #1
Hmmm, for some reason the above post didn't attach my name to it.  Oh well, It's DJ Skelding from Safeguard Inspection Services just in case ya'll wanted to know.
5:37pm • #2
APR
05
2007
1 Featured Post
I see 12 gauge wire multi tapped onto the main lugs. NO BREAKER. Supplies the garage power. "It's been that way for years and never had a problem" Ever hear that before on your inspection??? What an answer.
12:34pm • #3
MAY
15
2007
 Sometimes it may be ok, but its best to flag it and recommend further evaluation by an electrician.
11:06am • #4
OCT
14
2008

The national electric code (NEC) specifies that 12 guage wire has a maximum rating of 25 amps, so 1  12AWG connected to a 40 amp breaker violates code and should be fixed as it could potentially cause a fire in that circuit. Especially as the insulation ages, and becomes less fire retardant. That is also based on the wire being copper and not aluminum. There is a 15% penalty in power ratings for aluminum wire.

Yes, it is common for do-it-yourselfers to hook 12awg into any size breaker, depending on what they find cheapest when they do the job. It still violates code and definately should be addressed at the earliest convenience.
Jerome Daniher
10:42am • #5

Jerome Daniher

"The national electric code (NEC) specifies that 12 guage wire has a maximum rating of 25 amps, so 1  12AWG connected to a 40 amp breaker violates code and should be fixed as it could potentially cause a fire in that circuit. Especially as the insulation ages, and becomes less fire retardant. That is also based on the wire being copper and not aluminum. There is a 15% penalty in power ratings for aluminum wire.

Yes, it is common for do-it-yourselfers to hook 12awg into any size breaker, depending on what they find cheapest when they do the job. It still violates code and definately should be addressed at the earliest convenience."

Let us take your points one by one.

•1)      "The national electric code (NEC)"

•·          90.1(C) Intention. This code is not intended as a design specification or as an instruction manual for untrained persons.

•2)      "specifies that 12 guage wire has a maximum rating of 25 amps."

•·         Which table in 310.15 are you using?

•·          In some places that value is as high as 30 AMPS. Or 35, 40,60,68,78 and others.

•·         Other Articles will list the maximum amps and loads.

•3)      "so 1  12AWG connected to a 40 amp breaker violates code and should be fixed as it could potentially cause a fire in that circuit"

•·         Please cite a code reference.

•·         I listed Article 440 of the NEC © as an example of an exception.

•4)      ".Especially as the insulation ages, and becomes less fire retardant. That is also based on the wire being copper and not aluminum. There is a 15% penalty in power ratings for aluminum wire."

•·         This may be true but how does a Home Inspector determine this?

•5)      " Yes, it is common for do-it-yourselfers to hook 12awg into any size breaker, depending on what they find cheapest when they do the job. It still violates code and definately should be addressed at the earliest convenience."

•·          We can not protect people from being stupid.

My post/blog was to show why ALL information should questioned.

People like yourself harm real estate deals because you want to pretend that you are an expert.

Yes this is harsh but false information costs everyone money.

Example a Home Inspector says the electric has a problem. The electrician says no problem. Now you have to call in an expert like me to set the record straight.

Realtors ® surround yourselves with experts.
8:26pm • #6
NOV
26
2008

OK, So the code and the Bible have different interpretations by different people.  Mostly those who like to argue. 

Let me just take # 5 for example.  The law suite states "the defendant knew or should have known".  People expect to be protected fro their own stupidity.

No one has noted what load is on the circuit, motor, convince, kitchen, work shop.  I do my best to error on the side of caution.

If the client wants an electrical code inspector to do their home inspection they should hire one but then who is going to do the roof, plumbing, furnace and foundation?
10:47am • #7
FEB
13
2009

I like to manage my Clients' expectations by telling them that "I am a generalist, not an expert in anything. What that means to you is that I know something about everything and everything about nothing." That always gets a chuckle, helps break the ice, and lets them know what I can and cannot do, what I do and don't do, and, when it comes to personal safety and property damage, what I will and will not do.
6:14pm • #8

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Inspector Mike Parks

Circleville, OH

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Residential Building Inspectors

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As a Residential Building Official and a Electrical Safety Inspector I receive information on home related issues before the public is made aware of these changes and will share them here as they develop.While I am based out of Columbus Ohio I can help you in other areas of Ohio.



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