Main bonding jumper bus

[hhsting]

I have 4000A main service enclosed circuit breaker listed which has main bonding jumper as bus. The incoming service conductors are 13 sets of 4#500 kcmil which if main bonding jumper were wire requires 900kcmil cable.

Engineer did calculation of bus is copper 1/4”x4”width and area of bus is 1 square inches. 1 square inches to kcmil is 1273 kcmil. So the bus is okay.

I have following questions:

1. I thought manufacturer provided bus does not need calculation. Am I correct or not?

2. If manufacturer are providing bus as main bonding jumper then want if someone provides incoming service conductors any size they want can the manufacturer provided bus size Ever be small if someone connects service conductors oversized? I mean how do we know what the main bonding jumper bus is tested under what maximum incoming service conductor size.

 

[electrofelon]

I think if manufacturer provides bus or bar for MBJ it is good for anything. I assume there is something in the product standard (Is this a switchboard? If so UL 891?) That the manufacturer used for MBJ calculation.

 

[hhsting]

I think if manufacturer provides bus or bar for MBJ it is good for anything. I assume there is something in the product standard (Is this a switchboard? If so UL 891?) That the manufacturer used for MBJ calculation.

Yes its UL891

 

[infinity]

When we order 4000 amp switchgear the manufacturer knows what size and the number of sets the SEC's are going to be and builds accordingly. If you had a standard switchgear that accepts only 12 sets of conductors that not going to work when the engineer specifies 20 sets so they will know what size SEC's are being used when they build the switchgear. Knowing that information they can provide the proper size MBJ.