4 pole ATS

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hhsting

Senior Member
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Glen bunie, md, us
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Junior plan reviewer
I have 4 pole ATS. Normal side is fed by main service disconnect and emergency side is fed by generator 208/120V three phase has neutral going to the ATS. Same on normal side. The building has non balance loads so neutral is fed downstream from ATS.

Plans call for the generator to be Non separately derived. I am just confused.

Can one have 4 pole ATS and generator be Not separately derived?
 
NEC 100 Defines: Separately Derived System. An electrical source, other than a service, having no direct connection(s) to circuit conductors of any other electrical source other than those established by grounding and bonding connections.

A generator is a separately derived system by definition when used for as a secondary source.
 
As Rock notes, with a 4 pole T/S, your generator would be classified as a SDS and should follow 250.30 as to grounding.
 
If you wire the generator as a non-SDS, there will be no fault path to ground when on generator, a short circuit to ground will not trip the ocp until it transfers back to utility.
 
When you switch the neutral, each source should be bonded, and the load not bonded.

When you don't switch the neutral, each source should not be bonded, and the load bonded.
 
Now the plan designer is saying system bonding jumper comes factory installed in generator. I always thought one has to provide system bonding jumper wire type. I am confused do generator come with factory installed system bonding jumper or not?
 
hhsting said:
Now the plan designer is saying system bonding jumper comes factory installed in generator. I always thought one has to provide system bonding jumper wire type. I am confused do generator come with factory installed system bonding jumper or not?
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Some do, some don’t. Depends on how they are ordered. I have requested insulated neutral kits on ones that are non sds when they arrived with the neutral solidly bolted to the generator housing.
 
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