To run a new EGC or system bond

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Dbronx

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Colorado
A Generator with system bond installed with 400 amp OCD suppling a latrine unit. The service conductors are parallel two 3 conductor 4/0 with #4 ground, to a 400 amp panel, 250.122(F) states a #2 EGC is needed. Can the neutral conductor be used as the path by either installing a system bond jumper at downsream panel, with out removing bond in generator.
 
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Dbronx

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Location
Colorado
Can Neutral be used as fault current path?

Can Neutral be used as fault current path?

let me restate my question. A Generator with system bond installed with 400 amp OCD is suppling a latrine unit. The service conductors are two parallel cables 3 conductor 4/0 with #4 ground, to a 400 amp MDP, 250.122(F) states a #2 EGC is needed. Can the 4/0 neutral conductor be used as the fault path by installing System bond jumper at MDP, and removing the Equipment bond jumper and System bond jumper in generator. And would the System bond have to be 2/0​
 
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raider1

raider1

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Logan, Utah
Dbronx said:
let me restate my question. A Generator with system bond installed with 400 amp OCD is suppling a latrine unit. The service conductors are two parallel cables 3 conductor 4/0 with #4 ground, to a 400 amp MDP, 250.122(F) states a #2 EGC is needed. Can the 4/0 neutral conductor be used as the fault path by installing System bond jumper at MDP, and removing the Equipment bond jumper and System bond jumper in generator. And would the System bond have to be 2/0​
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Again I will say No it can't.

The breaker in the generator is the first overcurrent protective device for this separately derived system. 250.30(A)(1) requires that the system bonding jumper be installed either at the source of the separately derived system or the first disconnecting means. Since the generator has a built in breaker that would be the first disconnecting means and the system bonding jumper must be installed at that point. Once the separately derived system conductors terminate in an overcurrent protective device the conductors from that OCPD to the latrine unit would be feeder conductors. 250.32(B)(2008 NEC) requires that the feeder supplying a building be supplied with a equipment grounding conductor.

So with that said you need to have a full sized equipment grounding conductor in each cable.

Chris
 
ceb58

ceb58

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Location
Raeford, NC
raider1 said:
Again I will say No it can't.

The breaker in the generator is the first overcurrent protective device for this separately derived system. 250.30(A)(1) requires that the system bonding jumper be installed either at the source of the separately derived system or the first disconnecting means. Since the generator has a built in breaker that would be the first disconnecting means and the system bonding jumper must be installed at that point. Once the separately derived system conductors terminate in an overcurrent protective device the conductors from that OCPD to the latrine unit would be feeder conductors. 250.32(B)(2008 NEC) requires that the feeder supplying a building be supplied with a equipment grounding conductor.

So with that said you need to have a full sized equipment grounding conductor in each cable.

Chris
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First I will say that I totally agree with Chris's statement. But we have some communication sites where the generators were installed as separately derived systems. The contractors did not bond in the generator at the disconnect, they bonded in the generator fusible disconnect on the building. I questioned the state inspector, who has sat on the CMP, as to why he allowed it. His explanation was they consider the generator as the SOURCE and the disconnect would be the first in line. But he went on to say if they had bonded in the generator it still would have passed
 
ActionDave

ActionDave

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ceb58 said:
First I will say that I totally agree with Chris's statement. But we have some communication sites where the generators were installed as separately derived systems. The contractors did not bond in the generator at the disconnect, they bonded in the generator fusible disconnect on the building. I questioned the state inspector, who has sat on the CMP, as to why he allowed it. His explanation was they consider the generator as the SOURCE and the disconnect would be the first in line. But he went on to say if they had bonded in the generator it still would have passed
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That's the way we have done it also.
 
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Dbronx

Senior Member
Location
Colorado
Thanks for the help, just trying to come up with a solution other than diggig up the cables. If there was no system bond or OCPD at 220 kw generator, the MDP at latrine would be first means of disconnect the system bond could be installed. The cable would have to be 115% to first means of disconnect, that would mean two 3C 400 MCM with 2/0 Equipment bond jumper.
 
ceb58

ceb58

Senior Member
Location
Raeford, NC
As I stated the state inspectors I deal with allow the bond to be at the first disconnect which would be your MDP. By them taking the stance that the generator is the source and the breaker on the gen. is to protect the gen. they see the disconnect as the first one.
 
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heyrendelectric

Member
Location
Evanston Wyoming
I am new so please forgive me if I missed soemthing. Is the neutral conductor beinging switched at the generator? If it is not then it is not a seprately derived system and should not be bonded at the generator.
 
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