Home>Discussions>ELECTRICAL & LIGHTING>how to tell stranded wire size. #6 or #8 ?? No markings. 50 amp
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Rpm90001
how to tell stranded wire size. #6 or #8 ?? No markings. 50 amp

Hello everyone,

I have a question on wire size on old wiring that I can not see any markings on.

My mother bought a house next to ours and it had the original built in electric stove ( mid 60s) oven and 4 burners. I removed the cabinet and stove that was direct wired and installed a flush mount receptical in the wall so I can buy a new stove.

Here is my issue.. When I shut the power off I noticed the range was on 2 30 amp breakers. I believe new stoves need 50 amp. I have a 50 amp breaker but need to confirm wire size. It very heavy stranded wire. How can I confirm what wire i have? I believe i have to have #6. I want to be 100% sure. The wire has the Gray/silver cloth sheath and if it was marked, I do not see anything now. 3 wire & ground. Thanks for any help

Geo

dj1
Re: how to tell stranded wire size. #6 or #8 ?? No markings. 50 amp

One way is to expose the wire (turn power off) and use a stripping hand tool with size markings to determine the wire gauge. Another way is to compare the wire to a chart you can download from the internet.

Rpm90001
Re: how to tell stranded wire size. #6 or #8 ?? No markings. 50 amp

Thanks, trying to find a gauge. The wire is stranded not solid. When the charts show a wire size I can't tell if its stranded. I going to take a piece to the store and just try to match it. It should be a clear difference between 6 and 8. I just never worked with 6 gauge to know the difference by looking at it.

Re: how to tell stranded wire size. #6 or #8 ?? No markings. 50 amp

#6 stranded is 0.184 inches in diameter, slightly smaller than a 3/16" drill bit (0.1875")
#8 is 0.146" , slightly smaller than a 5/32" drill bit (0.15625")

Grey sheath indicates it is SE or Romex so, if it's #8 can handle 40A and if #6 can carry 55A. The insulation on this wire can't carry as much current as wire such as THHN etc.

The formula for Amps=watts/voltage
Med size Range: A=8000/240=33.3A
Large Range: 12000 Watts = 50A

Check the nameplate on the new range, so you don't buy one too large for the existing wire.

Leave the jumper, on the new range in-place from the neutral to the ground, since you only have a three wire feed to her range.

Rpm90001
Re: how to tell stranded wire size. #6 or #8 ?? No markings. 50 amp

Thank you. I just got started again on this issue. Kitchen is done time to get the new stove. Here is what I have done. I went to HD and tried to match up the wire but have a few questions.

1) I got a piece of stranded #10 and #8.
2). Visually 10 looks to small and # 8 looks correct.
3) used my plastic drill gauge, stripped a section on all 3 pieces. #10 7/64. #8 9/64 My sample piece 9/64
4). Used micrometer, i got O.141 on my sample and the #8 hd sample. The # 10 was 0.112. Numbers may very slightly due to wire being stranded.

Now I have 2 questions. If my measurements are correct? Am I safe to assume I have 8 gauge and can swap the 30 breaker with a 40 and add a 40 amp stove?

And second, my sample wire only has 7 thicker strands to make up the wire. The sample piece #8 wire I got form HD has thinner strands but about twice as many strands, about 14. Is there a performance difference in the type of strands a wire has. Does this effect anything with my measurements?

Thank you for you help, I know I'm makings bigger deal about this than I should be. I just want to be100% sure.

The wire 3 wire with ground. Click picture below for bigger picture. There is some other pictures if you use the arrow when you open the picture

dj1
Re: how to tell stranded wire size. #6 or #8 ?? No markings. 50 amp

To answer you latest questions:

1. #8 wire will handle 40 amp.
2. #8 Solid wire or #8 stranded wire - they can carry the same.

Rpm90001
Re: how to tell stranded wire size. #6 or #8 ?? No markings. 50 amp

Thank you.

I understand #8 is 40 amp, and solid and stranded is the same. Is there a difference in the amount of strands inside the wire? Say..7 thick strands vs 14 strands if the od of the wire is the same? Thanks.

Geo

dj1
Re: how to tell stranded wire size. #6 or #8 ?? No markings. 50 amp
Rpm90001 wrote:

Thank you.

I understand #8 is 40 amp, nd solid and stranded is the same. Is there a difference in the amount of strands inside the wire? Say..7 thick strands vs 14 strands if the od of the wire is the same? Thanks.

Geo

No difference if there are 7 strands, 14 strands or 1 solid, as long as they are all #8.

Rpm90001
Re: how to tell stranded wire size. #6 or #8 ?? No markings. 50 amp

That's my problem. The wire is not marked. And was on a 30 amp breaker with the original built in stove. I need to confirm the wire run through the walls is # 8. 30 amp normally would be 10. My hope is that it was over sized wire for the 30 and I can replace it with a 40.

Geo

Mastercarpentry
Re: how to tell stranded wire size. #6 or #8 ?? No markings. 50 amp

The number of individual strands has nothing to do with the gauge size, and the gauge size is what sets the rated current-carrying capacity. If it still worries you, then find an electrician who can confirm the size for you. More than likely they can do this at a glance with a matching price.

Phil

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