Old house-what gauge wire?

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Old 12-01-13, 07:53 AM
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Old house-what gauge wire?

Hello,

I have a house that was built in 1931. I need to splice in at a junction box, but I can't figure out if the old wiring is 14 or 12 gauge. It has a cloth outside and some kind of brittle coating over the wire. There is 12/2 run to it right now, but I'm not sure that's the right thing. I've attached a pic. Thank you!

Tom
 
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Old 12-01-13, 07:59 AM
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The cloth wire appears to be 14 gauge. More importantly, what is the amperage rating of the breaker/fuse that protects the circuit? If it is 15 amp, you're OK. If it's 20 amp, you need to replace the cloth covered wire with 12 gauge to its destination/origin.
 
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Old 12-01-13, 08:17 AM
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I have a house that was built in 1931. I need to splice in at a junction box, but I can't figure out if the old wiring is 14 or 12 gauge. It has a cloth outside and some kind of brittle coating over the wire. There is 12/2 run to it right now, but I'm not sure that's the right thing.
What are you doing? Just keep in mind that you cannot extend an existing ungrounded circuit.
 
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Old 12-01-13, 08:23 AM
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Hi Chandler. There is a mix of breakers in the box, some 20 but most 15 amps. The previous owner has both 12/2 and 14/2 running from the box and then tying into the old wire. I'm not comfortable with this. The pic shows 12/2 running from a 20 amp to the old wire, which then carries on into the house.
Thanks!
Tom
 
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Old 12-01-13, 08:35 AM
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Just keep in mind that you cannot extend an existing ungrounded circuit
Hi Joe. The old wire powers the garage, attic, two bedrooms, main bathroom, and basement (I am currently running new wire to the bathroom and bedrooms). However, there are two issue I am dealing with here 1) Is the 12/2 running from a 20 amp too much for the old wire running into the rest of the house and should it be 14/2 on a 15 amp? 2) I am trying to get power to a 3 way switch, and the third wire entering the box (on the right) is the power I need to tie into to get it working. I am trying to determine gauge so I know whether to spice in 12/2 or 14/2 for the 3 way.

Thanks!
Tom
 
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Old 12-01-13, 08:46 AM
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As said check the breaker. If you have the possibility of a mix of #14 and #12 change the breaker to 15a if it is 20a. As said it isn't code compliant to tie new wire to it for a circuit if the existing wire doesn't have a ground.
 
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Old 12-01-13, 09:19 AM
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Thanks Ray. That changes my schedule! I have what I have in regard to tying into ungrounded wire, but I'll switch out the #12 for #14 and bump the breaker down to 15a. There is one other new wire to old tie-in that I've inherited that powers the main portion of the house, and I'll swap that out as well.

I don't think I can afford an electrician to change out the old stuff, so short of what I'm doing, any other things I can do to make the situation safer? I'd appreciate your thoughts.

Tom
 
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Old 12-01-13, 10:00 AM
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You can check the wire gauge with a pair of wire strippers or against a known size piece.
 
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Old 12-01-13, 10:30 AM
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Just to add. The reason we are telling you to downgrade your breakers is if you are protecting the circuit with a 20 amp breaker, leading with 12 gauge wiring, then your 14 gauge becomes your fuse, and it most likely won't trip the 20 amp breaker when it overheats and possibly causes damage. Just for info.
 
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Old 12-01-13, 05:10 PM
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Thanks Chandler, I understand why you are saying that and I appreciate it. I don't particularly want another job (got plenty) but it's worth doing right when it comes to electrical...even if it's a bit of a pain in the butt.

You can check the wire gauge with a pair of wire strippers or against a known size piece.
I appreciate the wire stripper tip, but it seems that the old #14 wire I'm pulling out seems thicker than the new stuff. Is it just me smoking crack or is there a difference?

Thanks Again,
Tom
 
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Old 12-01-13, 05:28 PM
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The wire gauge standard has been the same for as long as I know. The insulation thickness and composition has changed though.
 
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Old 12-01-13, 05:46 PM
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Thanks pcboss, that must be it!
 
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Old 12-01-13, 05:58 PM
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Check the actual conductor, not the insulation.
 
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Old 12-01-13, 07:41 PM
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Yeah, I had an inspector call me out on a bathroom wiring job once. He was 45' away from a bathroom telling me I had to install 12 gauge in the bathroom. This was before they went to colored sheathing. I had to actually take him to the bathroom with my Kleins and strip a wire for him to prove it.
 
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Old 12-02-13, 07:38 AM
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Is the 12/2 running from a 20 amp too much for the old wire running into the rest of the house and should it be 14/2 on a 15 amp?
Just so you know, it isn't a code violation to feed existing 14-2 with new 12-2 w/G NM cable as long as the circuit is protected with a 15 amp breaker, but it isn't a good practice. If you do this, it would be very easy for someone in the future to think the whole circuit was suitable to be upgraded to a 20 amp breaker.
 
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Old 12-03-13, 09:07 AM
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The deed has been done! To be on the safe side I switched out the #12 for #14 and popped in a 15a breaker in place of the 20.

Thanks everyone for your help and advice.

Tom
 
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Old 12-03-13, 11:01 AM
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Thanks for letting us know how it was resolved.
 
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