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 Post subject: Wire Size
PostPosted: Thu Jan 02, 2014 12:37 pm 

Joined: Thu Jan 02, 2014 12:32 pm
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I have ran into several conductors that are old enough that the size can not be read on the insulation. How do you tell what size the wire is? I am unable to disconnect and actually measure it.


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PostPosted: Fri Jan 03, 2014 7:00 am 
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One method is to assume that the conductor is sized properly for the protective device it is connected to (or vice versa). Then knowing the length of the conductor, you can input one size up or down in the software and see how much of a difference it makes on the arc flash. This will of course not tell you if you are code compliant for protecting the conductor.

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PostPosted: Fri Jan 03, 2014 1:09 pm 

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That is what I am doing now, but with the age of the plants I am responsible for, assuming code compliance is a stretch.


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PostPosted: Fri Jan 03, 2014 1:47 pm 
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I understand that but just document your assumptions and I think for the most part even going up or down 2 sizes will not make significant difference.

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PostPosted: Mon Jan 06, 2014 7:07 am 
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Ryan McKee wrote:
That is what I am doing now, but with the age of the plants I am responsible for, assuming code compliance is a stretch.


Why do you think that?
What percentage of your identified conductors have been misapplied?


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PostPosted: Mon Jan 06, 2014 8:59 am 
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Another option is to purchase a set of non-metallic digital calipers and measure the conductor diameter. Then you look up the conductor diameter and make a logical assumption of the wire size. This will at least give you a pretty sound basis for your assumptions and you should be able to identify conductors that are not protected in accordance with the NEC. We did this for several old plants and the work goes pretty quickly. In our case, all of the measurements were made with the 40 cal. flash suit on due to the nature of the work and the location of the measurements. Some areas will be too dangerous to do this type of work, even with the 40 cal. suit.


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PostPosted: Mon Jan 06, 2014 2:30 pm 

Joined: Thu Jan 02, 2014 12:32 pm
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Thank you.
I understand a size up or down has the potential to make very little difference, but it goes against my perfectionism. I put in a request for some non-conductive calipers.
Again Thank You


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PostPosted: Mon Jan 06, 2014 3:40 pm 
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I can understand that but I don't like the risk with sticking something into a panel and then you risk the possibility of encountering a loose wire and possibility creating an arc flash.

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PostPosted: Mon Jan 06, 2014 5:19 pm 

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If you can de-energize the circuit, you could use a very handy device called a "Wire Mike". It is a "Burndy" product. Part # RK194-2. I have carried one in my tool pouch for years.


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PostPosted: Mon Jan 06, 2014 9:32 pm 
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Quote:
I have ran into several conductors that are old enough that the size can not be read on the insulation. How do you tell what size the wire is? I am unable to disconnect and actually measure it.


I would consider removing and replacing the conductors if the insulation is old and has deteorated.

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PostPosted: Tue Jan 07, 2014 6:10 am 
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WBD, I agree that you must be extremely careful when doing this type of investigation. We weren't checking small gauge wires that are more likely to come loose. These were large gauge conductors in switchgear with visibly well-crimped lugs. We were also very careful to measure the cables in a manner where we didn't have to disturb their positioning. That said, Steve makes an excellent point; deenergizing is your safest bet!


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