Emergency Generator ? separately derived with 4 pole transfer switches

[tombrinson]

On the normal system ?
The neutral and ground are bonded at the ?3000A - MSB?, at the1^st over current protection device
On the emergency system ?
800 KW generator with a 1200A breaker feeding an
emergency distribution panel ?EMDP.? The panel then feeds multiple 4 pole
transfer switches. The emergency generatoris treated as separately derived system. The 1^st over current devices would be the breakers in the ?EMDP.?
My question is do I bond the neutral and ground -
1. At the generator?
2. At the EMDP panel?
3. Both?

See attached Diagram-
View attachment Transfer Switch3.pdf

 

[tom baker]

At the generator there will be a system bonding jumper and a grounding electrode system.

 

[Smart $]

On the normal system ?
The neutral and ground are bonded at the ?3000A - MSB?, at the1^st over current protection device
On the emergency system ?
800 KW generator with a 1200A breaker feeding an
emergency distribution panel ?EMDP.? The panel then feeds multiple 4 pole
transfer switches. The emergency generatoris treated as separately derived system. The 1^st over current devices would be the breakers in the ?EMDP.?
My question is do I bond the neutral and ground -
1. At the generator?
2. At the EMDP panel?
3. Both?

See attached Diagram-
View attachment 8063

Your diagram shows N-G bonding at both the generator and the EMDP. Can't be both!!!

If there is no overcurrent device at the generator, as depicted, I recommend removing the N-G bond at the generator. Every thing else, though not scrutinized, appears okay.

 

[ceb58]

Your diagram shows N-G bonding at both the generator and the EMDP. Can't be both!!!

If there is no overcurrent device at the generator, as depicted, I recommend removing the N-G bond at the generator. Every thing else, though not scrutinized, appears okay.

That would be my question also. Dose the generator have a built in OCD? If not then you need to look at 445.13 too.

 

[harsha1972]

Why is the generator connected to ATS via EMDP? EMDP should be on the ATS common terminal while the generator is directly connected to ATS's emergency terminal.

 

[Smart $]

Why is the generator connected to ATS via EMDP? EMDP should be on the ATS common terminal while the generator is directly connected to ATS's emergency terminal.

I believe the diagram only depicts one representative ATS, and there are several actual ATS's.

 

[tombrinson]

Revised

Revised

To answer a few of the questions posted -

1. There are a total of 4 transfer switches.
2. 1200A/3P breaker at generator


The neutral/ground bond would be at the generator only.

See revised sketch.

 

[Smart $]

...

See revised sketch.

The only problem I see is the lack of a GEC. All grounding electrodes must be bonded together when present at the building. Connected via EGC doesn't count.