15 amp wire in 20 amp cir

[M. D.]

If I had to guess as to why 240.4 (D) is in the book I would say it is likely to be due to crappy conductor insulation and the advent of insulating homes colliding back in the day,.Just a guess.

 

[sguinn]

Anytime that I get a homeowner who wires their own house, one of the first things that I see is 14/2 switchlegs and 14/3 travelers with 12-2 feeding the circuit. I tell them it's a violation and then they ask why. That's usually when I ask them what edition of the NEC they own. . But actually, I have several ECs, when I first started inspecting that said "but the old inspectors let us do it that way". That's when I usually ask them what edition of the NEC they own. Then the usual reply is "well can I just put this circuit on a 15 amp breaker, that way I don't have to remove all this wire and pull new?" The code allows for this and I reluctantly agree unless it is for bathrooms. Here is my thoughts on this though, unless it's for a voltage drop etc. I feel that this is an unsafe practice because if the breaker wears out or malfunctions and an EC who didn't perform the install is called in, he will see the 12-2 tied onto a 15 amp breaker and then think someone made a mistake and then replace it with a 20 amp breaker.

 

[peter d]

I feel that this is an unsafe practice because if the breaker wears out or malfunctions and an EC who didn't perform the install is called in, he will see the 12-2 tied onto a 15 amp breaker and then think someone made a mistake and then replace it with a 20 amp breaker.

If an electrician decides to upsize a breaker without investigating the circuit first, he should consider finding another career. We shouldn't start making "what if's" to protect the unqualified and untrained.

 

[Jim W in Tampa]

If i so want i will run #10 home runs and branch off with #14.Long as i fuse at 15 you better pass it.As for what the next sparky does is not my problem .It is yours if he pulls a permit and your sharp enough to catch it.Till it happens there is no violation.On large commercial jobs i often must up size the hr

 

[480sparky]

Any electrician worth his/her salt will know that wire size and breaker ampacity is not hand-in-hand. Yes, you cannot use #14 on a 50a breaker, so a real electrician will correct that if they ever find it. On the other hand, a real electrician should be able to look in a panel and ask (and correctly answer!), "Now why is there #6 landed on this 20-amp breaker?"

Upsizing is so common in commercial and industrial, you routinely find 10s, 8s, 6s, even 4s on a 20-amp breaker. A couple years ago, I wired an entire 625-seat high school auditorium/stage/backstage & more and used only about 5000 feet of 12 THHN. Everything else was 10, and all the lighting you see here is wired with 8.

 

[peter d]

A couple years ago, I wired an entire 625-seat high school auditorium/stage/backstage & more and used only about 5000 feet of 12 THHN.

By yourself???

 

[Jim W in Tampa]

That had to be fun on a lift that high on tilted floor.

 

[480sparky]

That had to be fun on a lift that high on tilted floor.

No lifts were allowed.

 

[andinator]

Did you crap wings and fly?

 

[480sparky]

By yourself???

I wish! I had a crew of 6 regulars, and sometimes as many as 12.

Did you crap wings and fly?

Scaffold!

 

[tallguy]

I feel that this is an unsafe practice because if the breaker wears out or malfunctions and an EC who didn't perform the install is called in, he will see the 12-2 tied onto a 15 amp breaker and then think someone made a mistake and then replace it with a 20 amp breaker.

I'm with peter_d for sure. That would be negligent... maybe not criminally so, but come on... Heck, when I see #12 on a 20A CB where the age of the panel and the home differ by more than 20 years I figure it is quite likely that there is some #14 in the circuit. Maybe I'm cynical?