Generator Switchboard

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infinity said:
This is my thought as well. Since there's an SBJ in the generator the load side of the generator terminals get wired just like the secondary of a transformer with no SBJ in the generator switchboard. Each raceway would contain an SSBJ based on the size of the conductors in each parallel raceway.

Last part of the equation, if each raceway where it enters the generator switchboard requires a bonding jumper from the EMT to the EGC bus that can be sized two ways,

One: each raceway would have a bonding jumper sized according to the conductors in each raceway or,

Two: a single bond jumper can be used for all the raceways based on 12.5% of the total kcmils of the parallel conductors.
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The standard connector and lock nut should be all you need for the raceway bonding, assuming the raceways are directly attached to a metal enclosure.
If you need to install some type of bonding, either way will work, but getting a lug on the bonding bushing for the 12.5% sized conductor might be an issue.
 
don_resqcapt19 said:
So with an indoor generator (SDS), you can only have a system bonding jumper at a single location.
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One note on applying 250. 30 A1 exception 2. Even if this were an outdoor generator you have to be careful applying this exception. It’s really intended in my view for applications that resemble an outdoor utility medium voltage transformer application but just aren’t because the customer happens to own the transformer. If you try to use this exception for something like a generator then you could have problems. If there is a common ground grid that everything is tied to then you could have parallel neutral current. If someone installs a communication cable between the enclosures then you might have parallel neutral current. If someone installs a battery charger or block heater from the building 120V branch circuits then you may have parallel current. Then of course if you had metallic wiring methods you could have parallel neutral current.

On services the code is perhaps intentionally less clear in saying that you can’t have “objectionable current.” When it comes to separately derived systems where you should have more ability to prevent such current, it seems perhaps on purpose more clear in saying that they’re prohibiting “parallel current.”

So even if this were an outdoor generator I would not use this exception. I think it’s made for where you have a simple transformer with one or two sets of conduit ran a long distance into a building service.
 
don_resqcapt19 said:
If you need to install some type of bonding, either way will work, but getting a lug on the bonding bushing for the 12.5% sized conductor might be an issue.
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I believe that this enters an open bottom switchboard so bonding of the raceways with bonding bushings is required. Someone use a #4/0 bare copper conductor to bond all 12 raceways.
 
I did some digging into the local code amendments and found this. It seems that they want the generator wired the same way as a service which would mean a bonded neutral in both the generator switchboard and in the generator itself. There should be no SSBJ's in the raceways between the two.

SECTION 700.10
Section 700.10 – Add a new section 700.10 to read as follows:
700.10 Conductors for Emergency Circuits.
(A) Ampacity. See 445.13.
(B) Installation of Generator Conductors. Generator conductors shall be installed in accordance with the requirements of Article 230.
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ActionDave said:
Well that's really weird. I wonder who came up with that local amendment.
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I agree. This is a New York City amendment. Doesn't make much sense but it partially explains why they have the neutral bonded in both the generator and in the generator switchboard. Not sure why they put those big green conductors in the raceways that are now parallel with the neutrals. :unsure:
 
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