Terminating feeder cables for line loss

[thinkerrick]

This is a typical problem for terminating parallel and oversize feeders for line loss.

Example: What is the proper way to terminate 6#350 on a 250amp circuit breaker?
The parallel #350 are for line loss. The 250 amp breaker cannot accomodate dual lugs etc.

#350 T&B pin connectors do not help. Can the #350's be decreased in sized at the 250amp circuit breaker?

thinkerrick

 

[winnie]

Lots of different ways to do this properly, for example setting a splice box and using multi-tap insulated connectors to join the parallel conductors together and to a final length of conductor suitable for the breaker.

One of the explicit 'no-nos' is trying to trim down the 350's to fit. I am sure that someone could come up with a suitably tested 'reducing method' and get it UL listed, but until such a method is tested and approved, all it will do is get a red tag.

-Jon

 

[partimer31]

I would contact the Burndy Company.

I have use there non-insulated lugs, that can take three conductor up
to 250 KCMIL. This is bolt on style lug.

I am sure they must have something that will work for you.

 

[iwire]

The 250 amp breaker cannot accommodate dual lugs etc.

Have you checked with the breaker manufacturer to see if they have a lug kit for those size conductors?

Usually they have two, three, some times four different lug options for breakers.

If that is a no go I would splice either inside the panel if there is space or set a box just outside the panel to splice in. You will not be seeing any meaningful voltage drop on a few feet of smaller conductor.

 

[thinkerrick]

That really is the question. I know inspectors do not want to see cut off strands etc, the breaker cannot accommodate dual lugs, but does the code/inspectors allow splicing 2#250 into 1 #250 that last short distance?
I am looking for the definitive NEC or Engineering practice that allows it. In this particular case, a 400 amp feeder breaker that can accept all the cable may have to be used and dialed down to the desired overcurrent protection.
thinkerrick

 

[winnie]

Nothing in the NEC prohibits changing the size of a circuit conductor in the middle of the run. You could have a 20A circuit that starts as 10ga wire at the breaker, gets spliced to parallel 250's for the bulk of the run (for voltage drop), and then gets spliced to 12ga wire for connection to the load. The NEC requirements are that the conductor be large enough to be protected by the breaker, and that the splices be suitable for the conductors.

A 250kcmil copper conductor has a 75C amapacity of 255A, and assuming no weird 'gotchas' would be suitably protected by a 250A breaker.

Running a single 250 kcmil copper conductor a short distance to a splice that joins to a pair of 350 conductors would be one reasonable approach for connecting these conductors to the breaker.

Note, however that there are a number of engineering details that would need to be answered to actually implement this approach.

For example, the breaker enclosure might not be large enough to accommodate the larger parallel conductors, in which case the splice might need to be made in a separate enclosure. It is possible that the breaker terminals might not be capable of handling the mechanical stresses of holding the larger conductors, in which case the small 'jumper' conductor would need to be long enough to isolate the weight of the large conductors from the breaker terminal, etc.

-Jon