Tool for sizing existing wire

Do they make a tool (like calipers) to identify existing wire. I have to go around to some buildings and make one line's of the existing gear, panels and wire. I know I am not going to be able to identify some of this wire, and I really don't want to guess. I would like to take a tool (like a caliper) and just measure the insulation. Any idea's, thought's or clues? I am sure there will be xhhn and thhn.
Thanks
Shawn
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
If you cannot read the wire type markings, your identification of the insulation type (and therefore relation of OD to conductor size) may be shaky. If you can read the wire type you should be able to read the size too.
Plastic calipers on bare wire would tell you very conclusively, although you would have to determine copper/tinned versus aluminum/plated by inspection.

Tapatalk!
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
If you cannot read the wire type markings, your identification of the insulation type (and therefore relation of OD to conductor size) may be shaky. If you can read the wire type you should be able to read the size too.
Plastic calipers on bare wire would tell you very conclusively, although you would have to determine copper/tinned versus aluminum/plated by inspection.

Tapatalk!
Why plastic calipers. ----

Cause there cheap?
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
Do they make a tool (like calipers) to identify existing wire. I have to go around to some buildings and make one line's of the existing gear, panels and wire. I know I am not going to be able to identify some of this wire, and I really don't want to guess. I would like to take a tool (like a caliper) and just measure the insulation. Any idea's, thought's or clues? I am sure there will be xhhn and thhn.
Thanks
Shawn
I have a gauge with several wire sizes on it. It is a round plate with holes. The corresponding AWG sizes are stamped on it at each hole. Can't remember the brand or where I got it. Maybe you could Google it.
You would have to have a free end to stick in the holes. You're job seems to require checking while connected so what I have probably wouldn't work for you.

Mine is buried in my van somewhere!:blink:
 
Yeah, the wire will be hot while I am working on it, and it won't be shut down. NFPA 70 will be followed and someone will be suited up. Basically a industrial client has a bunch of buildings and no one lines. They want someone to go around, investigate and make up a one line. I imagine some of the wire is going to be older and the markings non readable. So instead of my best guess, I was looking for a tool to measure the insulation of the wire and tell me what size wire it is. I have looked at the Burndy Wire Mike, but don't know if you have to measure the stripped wire. If you have to measure the wire, stripped, then it's not going to work. As I am not going to put a stainless steel caliper on a energized wire.
 

HackElectric

Senior Member
Location
NJ
Use a plastic caliper that has a locking feature. Then use the Burndy Mike to measure the plastic caliper.
 

J.P.

Senior Member
Location
United States
Maybe take some short sample pieces ranging from 3-750 and just hold them up close to the live conductors and gauge it that way?

Hopefully you can see the insulation type by the top of the lug by how thick it is. Most everything I see unless it's 30 years old is thhn.
 

Fulthrotl

~~Please excuse the mess. Sig under construction~~
Use a plastic caliper that has a locking feature. Then use the Burndy Mike to measure the plastic caliper.
http://www.quill.com/general-tools-dial-caliper/cbs/325492.html?cm_mmc=SEM_PLA_X_325492

use these, megger them before use to make sure they aren't conductive at all.
some plastics are.

get up next to the lug, there will be a little bit bare usually, etc.

and most of the wire will be similar.

so once you know one size od with the insulation present,
it'll get faster and easier to do.

i had to do single lines in a sewage treatment plant once.
this is what i used, with 1kv rubber gloves.
 
^^^^^^^^^^^^^^^^^I like it. I will just have to make sure the calipers I pick up is 100% plastic with no metal what so ever. Measure the bare conductor with the plastic caliper and compare it to the burndy wire mike.
Thanks
Shawn
 
Don't forget that solid, stranded and compact stranded wire of the same gauge will have different diameters.

From Wiki:

AWG gauges are also used to describe stranded wire. In this case, it describes a wire which is equal in cross-sectional area to the total of all the cross-sectional areas of the individual strands; the gaps between strands are not counted. When made with circular strands (see Circle packing), these gaps occupy about 10% of the wire area, thus requiring a wire about 5% thicker than equivalent solid wire.
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
I have a gauge with several wire sizes on it. It is a round plate with holes. The corresponding AWG sizes are stamped on it at each hole. Can't remember the brand or where I got it. Maybe you could Google it.
You would have to have a free end to stick in the holes. You're job seems to require checking while connected so what I have probably wouldn't work for you.

Mine is buried in my van somewhere!:blink:
That's what I have too.
 

electric_cal

Member
Location
California
Use a "Wire Mike". It is sold by Burndy Products. Catalog # RK194-2.
I have carried one in my kit for years.
If you use it on an energized circuit, just be very careful!!!! :thumbsup:
 
Back to the OP's subject.

He wants to be able to tell the AWG by measuring the diameter of the wire, insulation and all.

I don't think that's going to be possible as the insulation thickness will vary and so will the conductor diameter. Especially in old buildings. I have seen #6 with old shiny cloth insulation that you could barely get 3 of into a run of 3/4" EMT.

In summation, old R type will have thicker insulation than new THHN and new compact stranded conductors will be much smaller than circular stranded conductors.

I would never trust measuring the insulation to give an accurate indication of the AWG.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector
I agree that sizing the actual conductor (bare) is the only true way, but I have used calipers and Table 5 and found it to be fairly accurate.
 
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