#14 on a 20amp OCPD

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Joethecrow

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This question is in response to the failed RI inspection of cds9044. I understand it is the rule of the NEC, but I wanted a reason why #14 couldn't be accepted on the switch legs of a 20 amp circuit. The example I come up with off the top of my head is the chandelier in my own dining room. The fixture hangs from a chain and the wire running through the chain is #14. Is this basically not the same as using #14 from the switch. The other thing is, this same chandelier I'm thinking of has 6 bulbs in it. If they were 100 watt bulbs, the most amps this #14 would ever have on it would be 5 right? I know I'm probably all wrong in thinking this, but what am I missing. By the way I visit this forum everynight and I SO respect all of your knowledge. I learn something everyday! thanks for your thoughts.
Joe :):-?
 
The wire form the outlet box to the chandelier (factory wire) is considered a fixture wire and sized per Art 402 and is also covered by 240.(5)(B)(2).
The cable from the switch to the outlet box (and all wiring up to the fixture connection) is building wire and covered by 240.(D)(3)
 
According to my copy of McGraw Hills 2008 NEC Code Book a 20A breaker will not fully protect a 14 gauge conductor certain under fault conditions. 15A breaker is the maxium size.

Same for:
20A breaker - 12 gauge conductor
30A breaker - 10 gauge conductor
 
Joethecrow said:
This question is in response to the failed RI inspection of cds9044. I understand it is the rule of the NEC, but I wanted a reason why #14 couldn't be accepted on the switch legs of a 20 amp circuit. The example I come up with off the top of my head is the chandelier in my own dining room. The fixture hangs from a chain and the wire running through the chain is #14. Is this basically not the same as using #14 from the switch. The other thing is, this same chandelier I'm thinking of has 6 bulbs in it. If they were 100 watt bulbs, the most amps this #14 would ever have on it would be 5 right? I know I'm probably all wrong in thinking this, but what am I missing. By the way I visit this forum everynight and I SO respect all of your knowledge. I learn something everyday! thanks for your thoughts.
Joe :):-?
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What he did in that post was not at all like this. He simply oversized part of his 15 amp circuit. You can not have a 20 amp breaker on a lighting circuit with any #14 wire.
 
SG-1 said:
According to my copy of McGraw Hills 2008 NEC Code Book a 20A breaker will not fully protect a 14 gauge conductor certain under fault conditions. 15A breaker is the maxium size.

Same for:
20A breaker - 12 gauge conductor
30A breaker - 10 gauge conductor
Click to expand...

But I can use a 30 amp breaker with 14 for some applications.
 
iwire said:
But I can use a 30 amp breaker with 14 for some applications.
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unless you "interpret" it as 15 amp is max, "that will protect the #14 wire under certain fault conditions", which is correct.

If you put a 30 on it you probably have some other protection device in the circuit, ie. motor protection, unless you have a different idea?
 
iwire said:
I don't as 14 AWG is rated 20 amps.
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Bob, why do we say that ? It's the answer I would give, but, as we both know in most applications it's limited to 15 amps and it's 90? rating is 25.
If a test asked "what is the minimum size conductor you can use for a load of 25 amps", would the technically correct answer not be #14 ?
 
augie47 said:
Bob, why do we say that ? It's the answer I would give, but, as we both know in most applications it's limited to 15 amps and it's 90? rating is 25.
If a test asked "what is the minimum size conductor you can use for a load of 25 amps", would the technically correct answer not be #14 ?
Click to expand...

that question doesn't have enough info to answer it correctly.
 
Joethecrow said:
The fixture hangs from a chain and the wire running through the chain is #14. Is this basically not the same as using #14 from the switch.
Click to expand...
No it’s not. I realize you are not just looking for the “code” answer, but also for the physical reason they are different situations. My response is that the #14 hanging within the chain is mostly surrounded by air. That allows the wire to reject its heat more easily than a wire within a conduit can do. But I think the reason the NEC requires protection at 15 amps for a #14 wire that has an ampacity of 25 amps is simply that small wires are fragile.
Joethecrow said:
The other thing is, this same chandelier I'm thinking of has 6 bulbs in it. If they were 100 watt bulbs, the most amps this #14 would ever have on it would be 5 right?
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Yes, it would only have 5 amps. But that is not the whole story. It will also have the heat generated by a set of six 100 watt bulbs. Too much heat from bulbs can present more of a fire hazard than the heat generated within a #14 wire carrying 25 amps of current.
 
charlie b said:
.........But I think the reason the NEC requires protection at 15 amps for a #14 wire that has an ampacity of 25 amps is simply that small wires are fragile. ............
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The "small conductor" rule was introduced in the 1956 NEC when type RHH insulation was first listed.

The ampacity table at the time was Table 1 in Chapter 10, which had the following: "The current-carrying capacities for Type RHH conductors for sizes 14, 12 and 10 shall be the same as designated for Type RH conductors in this Table." This put 14, 12 and 10 at 15, 25 and 40 amps respectively.

In the 1959, the ampacity table was relocated and became Table 310-12. The ampacites were also changed for Type RH conductors, so this put 14, 12 and 10 at the ratings of 15, 20 and 30 amps we know today.
 
iwire said:
But I can use a 30 amp breaker with 14 for some applications.
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mivey said:
Yep. He walked right into that one.
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Fell face first is more like it.

What I actually meant to convey is that McGraw Hill states that for a 14 gauge conductor the maximum size breaker that provides adequate fault protection is a 15A. I did realize table 240.4(G) listed a multitude of exceptions.

I do not know what type of conductor McGraw Hill had in mind. Possibly a 60 degree conductor. I am curious what the temperature of a 14 gage conductor could acheive with a 40A breaker ahead of it during a fault that did not clear quickly, because the fault current is 45 or 50 amperes & cooks for 5 minutes or so...
 
SG-1 said:
I did realize table 240.4(G) listed a multitude of exceptions.
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Some people are of the the school that likes to ignore that 240.4 says "A though G" - I'm not one of them... Unless "specifically" covered in one of the codes listed in G - #14 is limited to 15A - the problem is there is nothing 'specific' to allow otherwise...
 
e57 said:
Some people are of the the school that likes to ignore that 240.4 says "A though G" - I'm not one of them... Unless "specifically" covered in one of the codes listed in G - #14 is limited to 15A - the problem is there is nothing 'specific' to allow otherwise...
Click to expand...

And some people cannot see the forest for the trees, IMO you are mistaken in your belief.
 
iwire said:
And some people cannot see the forest for the trees, IMO you are mistaken in your belief.
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Some people see lumber - And since it says exactly what it says, and nothing more can be implied by it - please find something "specifically" allowing otherwise...
 
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