Sizing MBJ and its material

[hhsting]

I have incoming service conductors of 3 sets of 500kcmil AL.

So to size MBJ I have 3x500=1500 kcmil. 1500x0.125=187.5kmil which is 4/0.

1. So then that 4/0 is it AL or Copper? Which material?

 

[Rough Draft]

4/0 AL. You only use the 12.5% rule when you're over 1750kcmil AL, but the answer is the same. See chart 250.102(C)(1) in NEC

 

[augie47]

The way I read the Table you could elect to use a 2/0 Cu MBJ.

 

[don_resqcapt19]

What are you using for service equipment? All equipment that is listed as "suitable for use as service equipment" has a factory supplied MBJ. You simply install the factory provided part and forget about any calculations.

 

[hhsting]

Didnt want to start another thread but what would the MBJ be in copper for service conductors of 3 sets of 500kcmil AL?

 

[infinity]

Didnt want to start another thread but what would the MBJ be in copper for service conductors of 3 sets of 500kcmil AL?

Look below:

Table 250.102(C)(1) Grounded Conductor, Main Bonding Jumper, System Bonding Jumper, and Supply-Side Bonding Jumper for Alternating Current Systems

 

[hhsting]

Look below:

It is not clear what size cu MBJ from the Table?

 

[roger]

It is not clear what size cu MBJ from the Table?

Read the notes to the table, you were given the answer in post #2

 

[infinity]

It is not clear what size cu MBJ from the Table?

What isn't clear? Right from the top of the table:

Size of Largest Ungrounded
Conductor or Equivalent Area for
Parallel Conductors
(AWG/kcmil)

Size of Grounded Conductor
or Bonding Jumper*
(AWG/kcmil)

 

[hhsting]

What isn't clear? Right from the top of the table:

2/0 awg?


Sent from my iPhone using Tapatalk

 

[infinity]

2/0 awg?

Yes, 1500 kcmil = #2/0 copper or #4/0 aluminum.

 

[don_resqcapt19]

Didnt want to start another thread but what would the MBJ be in copper for service conductors of 3 sets of 500kcmil AL?

Again I have to ask about the service equipment where you are installing the MBJ.

 

[qcroanoke]

What are you using for service equipment? All equipment that is listed as "suitable for use as service equipment" has a factory supplied MBJ. You simply install the factory provided part and forget about any calculations.

So are you saying the bonding screw can act as the main bonding jumper?

 

[augie47]

So are you saying the bonding screw can act as the main bonding jumper?

Factory supplied screw or strap. yes.

 

[infinity]

So are you saying the bonding screw can act as the main bonding jumper?

Don is asking if this is service equipment which typically has a factory supplied MBJ (screw, strap, bus bar). If so then why the question on how to size a wire type MBJ?

 

[don_resqcapt19]

So are you saying the bonding screw can act as the main bonding jumper?

Yes, the factory supplied screw is the main bonding jumper for equipment that is listed as "suitable for use as service equipment". The listing standard requires that the manufacture provide a main bonding jumper suitable for the rating of the service equipment. For the application in this thread it would not be a screw, but as bus connection or bus bar.

 

[don_resqcapt19]

Don is asking if this is service equipment which typically has a factory supplied MBJ (screw, strap, bus bar). If so then why the question on how to size a wire type MBJ?

Because the title of the thread is "Sizing MBJ and its material". I have no idea what he is really asking about. If you are connecting to listed service equipment, the manufacture is required to provide the main bonding jumper.

 

[Canton]

Because the title of the thread is "Sizing MBJ and its material". I have no idea what he is really asking about. If you are connecting to listed service equipment, the manufacture is required to provide the main bonding jumper.

It’s possible it was lost/misplaced on the job. I had to make a few MBJ in the past

 

[don_resqcapt19]

It’s possible it was lost/misplaced on the job. I had to make a few MBJ in the past

Unlikely that is the case with this poster...he is a plans examiner and does not work in the field.