Wire size in the field

[Keri_WW]

Any tips on determining the size of wire in the field where the wire may not be marked, may be in a difficult location to read if it is marked, or where it could be hazardous to get too close to the wire?

I'm getting into a bit of field work where this is starting to become problematic, and it is crucial to know the correct wire size that is installed.

Thanks so much!
Keri

 

[petersonra]

Any tips on determining the size of wire in the field where the wire may not be marked, may be in a difficult location to read if it is marked, or where it could be hazardous to get too close to the wire?

I'm getting into a bit of field work where this is starting to become problematic, and it is crucial to know the correct wire size that is installed.

Thanks so much!
Keri

the code requires conductors be marked. if it is not marked it is probably not to code.

you could try a micrometer if you can tell what kind of insulation it is. the manufacturer of the wire will have a chart that tells you what the OD is of the different sizes of wire.

if it is too hazardous to look at you are probably out of luck.

 

[Ponchik]

As suggested by petrsonra or you can try a caliper and compare your readings with manufacturer.

 

[Keri_WW]

the code requires conductors be marked.

Any idea when this became a requirement in the NEC? I have some buildings ranging upwards of 25-50 years old. :happysad:

The micrometer is a good idea; however, aren't most micrometers metallic?

One of the problems I am running into is that the cables are likely marked by the manufacturer, but the part I can actually see is wrapped with color tape to differentiate the phase.

 

[petersonra]

Any idea when this became a requirement in the NEC? I have some buildings ranging upwards of 25-50 years old. :happysad:

The micrometer is a good idea; however, aren't most micrometers metallic?

One of the problems I am running into is that the cables are likely marked by the manufacturer, but the part I can actually see is wrapped with color tape to differentiate the phase.

What difference does it make if it is metallic? You are not allowed to examine energized equipment anyway. the power has to be off so whether it is metallic or not makes no difference.

I have no idea how long this has been in the code, but a long time anyway. maybe 1950 ish?

 

[GoldDigger]

What difference does it make if it is metallic? You are not allowed to examine energized equipment anyway. the power has to be off so whether it is metallic or not makes no difference.

+1, although the OP might worry about metal calipers damaging the insulation if it is bad enough shape.

But, for what it is worth, there are inexpensive vernier calipers that are entirely plastic. No plastic micrometers though.
And none of them suitable for use at the end of a hot stick.
If the wires are in plain view, from a safe(?) distance you might have some luck with an optical device that lets you approximate the size better than a naked eyeball would.
Anyway, the hard part would be figuring out what kind of insulation and how thick if there are no type markings on the wire.

 

[petersonra]

+1, although the OP might worry about metal calipers damaging the insulation if it is bad enough shape.

But, for what it is worth, there are inexpensive vernier calipers that are entirely plastic. No plastic micrometers though.
And none of them suitable for use at the end of a hot stick.
If the wires are in plain view, from a safe(?) distance you might have some luck with an optical device that lets you approximate the size better than a naked eyeball would.
Anyway, the hard part would be figuring out what kind of insulation and how thick if there are no type markings on the wire.

I actually have a pair of plastic calipers for my reloading bench. they work pretty good.

 

[JoeStillman]

Tear a small strip of paper. Wrap it around the wire so it laps over a little bit. Make a mark at the overlap. Measure between the marks and divide by pi (3.142). The result is the outside diameter.

Measuring with calipers directly is potentially less accurate if the cables are bent because they loose their round profile.

 

[JoeStillman]

the code requires conductors be marked. if it is not marked it is probably not to code.

I can't tell you how many times I have seen cables that were marked at the factory, but are no longer legible. The marking scrapes off when they're pulled through a pipe.