120v electrical wiring

SVreX wrote: I was just looking for my NEC book and can't find it right now. I'll work on it tomorrow. Can you provide the reference you are referring to prohibiting 14 gauge in the walls on a 20A?

I go by the allowable ampacity tables in article 310, conductors for general wiring. Also, article 240-3.d which says 15 amps maximum for #14awg wire.

However, now that I look at it I see article 240-3.e has a tap conductor exception that leads to 210-19.d. There it talks about using an 18" long, #14 wire tap for light fixtures. From 210.19d there's a reference to article 410.67 where it talks about being able to use a tap that's longer than 18" but less than 6'.

Note that I'm looking at a 1999 edition of the NEC - it's all I have here at home, my newer books are at work so the specific article numbers may be slightly different in the newer versions.

So, it appears you're right - #14 wire can be used to a connect a light fixture to a 20 amp circuit, in some situations.

stuart in mn wrote: in some situations.

On that part, we most certainly agree!

I would also add that it is generally bad advice to tell someone they can use 14 gauge wiring with a 20A breaker, so I also agree with the rest of your input.

I'm just a rebel.

Wiring diagram looks right to me. I have done similar with the different wire sizes many times and had no problems.

I am concerned with the voltage when the GFI is tripped. I went and tested 2 similar circuits that I installed in my house. In both cases I only got .01 volts when the GFI was tripped.

I suggest trying another meter if you have one. If you get the same results with another meter I would get another GFI.

Hal wrote: Wiring diagram looks right to me. I have done similar with the different wire sizes many times and had no problems. I am concerned with the voltage when the GFI is tripped. I went and tested 2 similar circuits that I installed in my house. In both cases I only got .01 volts when the GFI was tripped. I suggest trying another meter if you have one. If you get the same results with another meter I would get another GFI.

Ok, thanks. I have an analog meter somewhere that I'll try.

As far as the 12ga to 14ga, I agree with the "fusing" part. Its not the greatest thing to do, but neither is anything else these builders did in 1937. Anything I do is an upgrade. When I cut the ceiling for the exhaust fan, three MC wires were in view. One was the old lead for the original light switch, and the other two were just stripped, soldered, and wrapped with fabric electrical tape.

But that poster is right... I now have 12ga wire feeding 14ga. If I (for instance) plug my pancake air compressor in that GFCI to do some nailing, I could be drawing 20amps. The breaker won't care, the 12/2 won't care, but that last leg of 14ga could overheat. I decided that if/when I sell the house, I'll just replace that breaker with a 15A so the new guy doesn't kill his family.

One of the fun parts I discovered was that a new panel with 100A service was installed and inspected in 2009, but three circuits have reversed polarity, and there is a 100A slave box in the kitchen that is supplied by a 40A breaker in the main box. Seriously people? I want whatever the inspector was having. The entire upstairs; outlets, lights, everything, (as well as all the first floor lights) is on ONE 20A breaker... but there is an entirely separate circuit made for one single outlet in the basement. I've ripped down the main wall that takes the conductors upstairs and I'm in the process of weeding them out, identifying them, and they will be separated if at all possible. After two months of tracing, following, and repairing what I could, I've determined that the only way to do it "right" is to rip out every single wall.

I'm tackling things one by one as I encounter them. I keep telling myself, "it hasn't burned down for 75 years."

Electrically speaking, this house is a MESS. Every electrical project I'm doing is a nightmare.

Pay no attention to wire size on a lighting fixture. The manufacturer goes by a different set of rules than the NEC in most cases. Actually so does the power company with the service drop cables. If the fixture has a UL stamp it is a-okay with the NEC even if it has 18 gauge wire(most do). I still stand by post stating that 14 gauge cable on a 20 amp circuit is dangerous regardless where in the circuit it is and illegal in maybe every state in the union. I know it is here in MA. But then again I am only a trained professional so don't listen to me. 15 amp rated outlets are allowed on 20 circuits here in MA, but that is another thing entirely.