350 MCM cable

[funseebee]

Is it against the NEC to cutoff strands of 350MCM to fit into a lug with max of 300MCM?:-?

 

[templdl]

YES!!!! Get the correct lugs!

 

[petersonra]

The answer is the code probably does not specifically prohibit this.

However, it is a violation of the instructions that come with the lugs as to the range of wire it can accept.

So, unless a lug came with instructions that said you could do this, the answer is no.

In the real world it is not unheard of for electricians to do this rather than go buy the right lug.

My guess is that in most cases it won't hurt anything, but its not right nor would it meet code.

 

[McDowellb]

If you cut the strands off its no longer 350 mcm. Why not buy the correct size lug or pin adapters.

 

[Bob NH]

I found a case in my son's house where some strands were trimmed from an AWG 3 THW used for the neutral for a 100 Amp feeder to a subpanel. The hole in the neutral bar of the service panel wasn't big enough to accept the #3.

 

[sandsnow]

I was once told the "correct" way to do this.

Fan out the strands and cut off the center ones, then fold outer strands back in.

Reason given: Electricity flows on the outside skin of the conductor.

Submitted for your enjoyment

 

[Minuteman]

I was once told the "correct" way to do this.

Fan out the strands and cut off the center ones, then fold outer strands back in.

Reason given: Electricity flows on the outside skin of the conductor.

Submitted for your enjoyment

Now we know the "correct" way to do it wrong.

 

[templdl]

The manufacturer supplies terminals that they have concluded will fit the common application. More often than not one assumes that a breaker will be supplied with terminals that will fit your application and we take it for granted when they do.
But there are times when ....."gotcha." Either one didn't know what cable was being supplied of failed to review the specifications for the breaker to determine what the standard terminals were and if they complied with the application, if there were terminal options. It is not all that uncommon for terminals to be replaced with ones that a suitable for the application.
A 400a frame breaker first comes to mind that may be supplied with line (2)3/0-250kcmil cu assuming a 400a trip unit. Then apply a trip unit that is suitable for a 350kcmil cable.
And when a 400a breaker is again suppied with (2)3/0-250kcmil cu terminals and (1) 500kcmil cu /ph has been pulled.

 

[sandsnow]

Now we know the "correct" way to do it wrong.

Kind of like a double negative so that would make it OK!?!?!?

 

[sandsnow]

The manufacturer supplies terminals that they have concluded will fit the common application. More often than not one assumes that a breaker will be supplied with terminals that will fit your application and we take it for granted when they do.
But there are times when ....."gotcha." Either one didn't know what cable was being supplied of failed to review the specifications for the breaker to determine what the standard terminals were and if they complied with the application, if there were terminal options. It is not all that uncommon for terminals to be replaced with ones that a suitable for the application.
A 400a frame breaker first comes to mind that may be supplied with line (2)3/0-250kcmil cu assuming a 400a trip unit. Then apply a trip unit that is suitable for a 350kcmil cable.
And when a 400a breaker is again suppied with (2)3/0-250kcmil cu terminals and (1) 500kcmil cu /ph has been pulled.

A job I was inspecting had this happen. The engineer upsized the conductors for voltage drop, so they had to splice minimum ampacity wire to get it to terminate in the lugs on the breaker which were the largest available.

The manufacturer was given the single line and feeder schedule.

While not common, it's not uncommon that I see this problem. I hope that makes sense.

 

[Minuteman]

Kind of like a double negative so that would make it OK!?!?!?

As long as it passes inspection!