Conductor missing strands

Smart $

Esteemed Member
Location
Ohio
I have an alum 600 Kcmil conductor (USE-2, 385A) that during installation had 2 strands of the 61 cut. I am trying to figure out the new ampacity of this conductor.
Where, why, how were they cut? If on the very end, is the conductor too short to just remove that portion and still make the connection? More details will help.

IMO the remedy is to just splice with compression connector and insulate as necessary.

Welcome :thumbsup:
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
I have an alum 600 Kcmil conductor (USE-2, 385A) that during installation had 2 strands of the 61 cut. I am trying to figure out the new ampacity of this conductor.
Well, let's see:
How about zero, since it has been modified illegally? :)

Often stranded conductors are modified by cutting back a couple of strands to get them into a lug or compression fitting that is not sized for that wire. Definitely not a good thing, and an inspector who notices it will probably fail it.

If somehow two strands were broken, under the insulation, in the middle of a long run of wire, the immediate effect would be negligible because the broken strands will be able to transfer current to the adjacent strands to bridge the gap. A slightly hotter spot in the wire, but little else.
If the two strands broke off because of careless stripping, I would also look for other strands that were nicked and might end up breaking.

Purely technically and theoretically, the conductor would have 59/61 of its original current carrying capability, but would not have a rated ampacity under the code since it would no longer be a recognized wire size of type.

As far as code compliance goes, just splice it!
 
I have an alum 600 Kcmil conductor (USE-2, 385A) that during installation had 2 strands of the 61 cut. I am trying to figure out the new ampacity of this conductor.
The conductor is going into a properly sized lug, @ the end of a 400 ft U/G run, the strand is cut. it is in the bottom lug of a DC combiner box w little room to spare As the inspector I want to be reasonable, so I am getting opinions before I make the contractor dig a up the run and possibly damage more conductors in the trench
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
If you are in a position to be kind to the contractor, the effect will really be minimal.
If the conductor has been oversized to reduce VD, the remaining ampacity will still be fine and the effect on VD will not even be detectable.
If this is part of a PV installation, it is very possible that the long DC run is oversized.
Are you confident that there are no additional cut strands that have been buried in the middle of the termination
?


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Smart $

Esteemed Member
Location
Ohio
...

Purely technically and theoretically, the conductor would have 59/61 of its original current carrying capability, but would not have a rated ampacity under the code since it would no longer be a recognized wire size of type.
Purely technically and theoretically, the conductor would have ampacity greater than 59/61 because ampacity per cmil ratio goes up as conductor size goes down. :happyyes:

As far as code compliance goes, just splice it!
Is there actually a Code requirement to be compliant with would be the first question. The conductor was likely upsized for voltage drop, so the minimum size required for terminal temperature coordination may still be well below 600kcmil minus two strands.

The conductor is going into a properly sized lug, @ the end of a 400 ft U/G run, the strand is cut. it is in the bottom lug of a DC combiner box w little room to spare As the inspector I want to be reasonable, so I am getting opinions before I make the contractor dig a up the run and possibly damage more conductors in the trench
To be technically correct, the NEC does not have any explicit and direct requirements for conductor ampacity in an enclosure.

If the conductor was upsized for voltage drop, missing two strands at the termination will not make a bit of difference. If you're going to lose sleep over passing it, have the contractor terminate the conductor with a size-reducing compression connector (sometimes called a pin terminal).
 
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steve66

Senior Member
For a termination, I would consider both the surface area of the connection, and the ability of the wire to wick heat away from the termination (which would run slightly hotter than the wire due to the additional resistance at the contact.)

I'm going to go out on a limb and and say the surface area probably won't change at all for only 2 strands missing. It would slightly reduce the wires ability to carry heat away, but only by 2/61's (at the most).

That's only 3%. If it were my call, I wouldn't worry about it.

As other have said, if the electrician intentionally cuts off enough to make it fit in a lug that's too small, I would consider that to be a different situation.
 
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