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Old 09-16-2013, 08:39 AM   #1
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Wire Gauge vs Breaker Size


Currently running a couple of shop lights in the garage and have a question.

From my limited knowledge a 15 amp breaker pairs with 14 ga. wire. I am using 14 ga since I have a 50 ft roll available.

I understand the point is that the breaker trips prior to wire overheating which could occur if a 20 amp breaker was used. I DID replace the existing 20 amp with a 15 amp. A well spent $8.00 from a safety point of view.

Here is what I don't understand. In the shop lights the wire seems to be maybe 16 or 18 gauge?

Isn't this a problem as the wire would overheat before the 15 amp breaker trips?

Is it just a matter of NEC providing maximum protection to a point. Clearly a lower amp breaker such as 10 would be better, wouldn't it?

Just wondering.

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Old 09-16-2013, 08:53 AM   #2
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Wire Gauge vs Breaker Size


Quote:
Originally Posted by drjay9051 View Post
Here is what I don't understand.
In the (UL approved) shop lights...
The NEC is concerned with the wiring in buildings... not fixtures.

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Old 09-16-2013, 09:00 AM   #3
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Wire Gauge vs Breaker Size


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Originally Posted by TarheelTerp View Post
The NEC is concerned with the wiring in buildings... not fixtures.
Understood. So this begs the question: Is the NEC overkill as the wire gauge in lights (UL approved) is clearly "inferior" as far as carrying a given current. Is this just a matter of 2 "governing bodies' not on the same page. I don't see how a fixture is UL approved if it is not safe? So again is the NEC just overly cautious? I am not suggesting circumventing the NEC but suppose I did not spend the $8 for my new 15 amp breaker. Seems like the wiring in the lights would be a problem not the 14 gauge romex?

Is this just one of those things we should accept at face value and not question?
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Old 09-16-2013, 09:44 AM   #4
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Wire Gauge vs Breaker Size


a lamp fixture cant draw 15 amp, it is a fixed load of maybe 1-2 amp maximum, thats why the use smaller wire. in case of short-circuit a 18 gage wire is able to trip a 15 amp breaker. also in chassis wiring (conductor in free air) a 18 gage could handle 10-15 amp easily
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Old 09-16-2013, 11:04 AM   #5
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Wire Gauge vs Breaker Size


Fixtures are pre-wired assemblies and are UL approved. Sometimes the wires insulation is superior and thus the smaller wire. There is no concern
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Old 09-16-2013, 11:25 AM   #6
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Wire Gauge vs Breaker Size


Fixture wires are covered in the NEC with the minimum size being 18 gauge. The 18 gauge wire is only carrying the current of one light but the 14 romex is carrying the current of all the lights.

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