Main service switchboard

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hhsting

Senior Member
Attached sketch shows incoming 11 sets of 750kcmil service conductors into main service switchboards MLO with (3) 800 A main service breaker and (1) 2000A main service breaker

Each 800A breaker has grounding electrode conductor to external bus bar and 2000A breaker has grounding electrode conductor to external bus bar

The bus bar has bonding jumpers to grounding electrodes

The 800A main service disco has 400kcmil AL and 2000A main service disco has 500kcmil AL as main bonding jumper


Questions:

1. Switchboard is one assembly instead of providing one main bonding jumper each service disco has main bonding jumper. Anyome have any idea as to how each Main bonding jumper is sized because their is incoming electric utility service but then its all one assembly? How they go 400kcmil and 500kcmil?

2. Switchboard is one assembly so should not their be one main bonding jumper Not in individual ones? I see it as exception but its not required so how does one size each main bonding jumper in each main service disco?

1ebc3ad71a3139f2567cd11d6cc9c00f.jpg
 

augie47

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Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
This is basically the same as your earlier thread:
except we are substituting "Main bonding jumper" for "bonding jumper for wirerway"
Both are covered by 250.102 and electrofelon gave you good answers last time.
I see no reason to reinvent the wheel and in 99%+ of the factory will provide A system bond jumper IF this is a Service Rated switchboard.
 

hhsting

Senior Member
This is basically the same as your earlier thread:
except we are substituting "Main bonding jumper" for "bonding jumper for wirerway"
Both are covered by 250.102 and electrofelon gave you good answers last time.
I see no reason to reinvent the wheel and in 99%+ of the factory will provide A system bond jumper IF this is a Service Rated switchboard.

It is not the same post my friend. This is not about wireways and cables into main service disco. Previous posts had cables and sizes into each main service disco this one does NOT

This one is about main service switchboard MLO and are providing four main service breakers in the switchboard assembly factory installed and they are providing main bonding jumper cables in each and grounding electrode conductor to external bus in each main service breakers. Not factory installed

If you have a switchboard with 4 main service breaker factory installed then how can you size main bonding jumper for each? The line side of each main service breaker is fed by internal bus factory installed.

Please see my post #1 questions
 
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augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
As I said, both the jumpers you were sizing in the other thread and the main boding jumpers are size by 250.102 so the answer would be the same.
 
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