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Wire size change same circuit


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I thought that if a circuit originates as a 12 awg then the entire circuit must be at least 12 awg.

Today I saw a new build where the electrician ran 12 awg to the GFCI at the panel and from that box he fed the exterior GFCI's through a 14awg.

The circuit was properly protected at 15 amps.

When I went to the NEC, I couldn't find anything to support my previous beliefs that one cannot reduce wire size.

If there is something in the NEC, would someone point me in the right direction?

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Long ago I knew an electric engineer who had worked at Oak Ridge during the slide rule era. He boasted that in a little home he built for him and his wife he had sized down conductors that way with such effect that the poco sent someone to investigate why his meter turned so slowly.

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I realize that in this case the circuit is protected, but I don't think it's improbable that in the future someone may replace the breaker with a 20 amp because the weed whacker keeps popping the 15 amp breaker.

In the past, I've up-sized breakers to the wire size in the panel. It's not likely anyone would ever trace the circuit to the lowest common denominator.

It's like starting with 3 inch pipe at the toilet and reducing the pipe to 2 inch pipe at the discharge.

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I thought that if a circuit originates as a 12 awg then the entire circuit must be at least 12 awg.

Today I saw a new build where the electrician ran 12 awg to the GFCI at the panel and from that box he fed the exterior GFCI's through a 14awg.

The circuit was properly protected at 15 amps.

When I went to the NEC, I couldn't find anything to support my previous beliefs that one cannot reduce wire size.

If there is something in the NEC, would someone point me in the right direction?

Unless the house is HUGE, making these runs very long, like 150'+, then all it is is a waste of money on the larger wire.
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It seems fairly likely to me that, in the future, if someone needed to replace the breaker, they would go with a 20 based on the wire size in the panel, without checking to see that all devices on the circuit were 12-gauge wire. In hundreds of remodels I don't think I've ever seen a circuit with two wire sizes.

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I'm agreeing with the folks who don't see a problem here. The NEC only requires that the smallest conductor of the circuit meet the minimum size based on the breaker. It considers what is there, not what some future worker might assume.

I've done several re-wiring jobs where we have replaced 12 or 14 gauge wire with home runs of 10 to reduce voltage drop. The first outlet on the circuit will have 10 coming from the panel, and 12 or 14 going to the other outlets in the room.

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Thanks Pete, but to be honest, you missed the question entirely.

How so.

OK, no, there is no prohibition to going up or down in wire size as long as the breaker is sized for the smaller wire. This point was already made so I did not make it earlier for fear of being redundant. I was just making an observation.

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Thanks Pete, but to be honest, you missed the question entirely.

How so.

OK, no, there is no prohibition to going up or down in wire size as long as the breaker is sized for the smaller wire. This point was already made so I did not make it earlier for fear of being redundant. I was just making an observation.

It seems counter-intuitive that it's allowed to start circuits with a large gauge and finish them with a smaller gauge when it's so likely that all the wiring will be concealed. I was trying to get a better answer from you to help me wrap my brain around the situation.

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I realize that in this case the circuit is protected, but I don't think it's improbable that in the future someone may replace the breaker with a 20 amp because the weed whacker keeps popping the 15 amp breaker.

In the past, I've up-sized breakers to the wire size in the panel. It's not likely anyone would ever trace the circuit to the lowest common denominator.

It's like starting with 3 inch pipe at the toilet and reducing the pipe to 2 inch pipe at the discharge.

Even though it's apparently not prohibited by written rule, I totally agree with your concern.

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I would have no issue if the circuit originated with a 14 and then went to 12.

Doug or Jim?

If it originates with 14 Im ok with it as its pretty obvious to somebody working inside the panel as to what size the breaker needs to be.

Its when they start with a larger wire and down size it in a junction box someplace down line that worries me.

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I originally told the electrician I was almost certain that the scenario was not allowed, but that I'd check. I called him today and told him he was right and I was wrong. The guy just started laughing- he thought it was hilarious. When he stopped, he told me that even though he knew he was right, he never thought I'd admit I was wrong so he sent guy back to change the wire from the panel to the receptacle.

Apparently he's used to BIs being full of crap and sticking to it.

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