ATS Neutrals

[rayertz]

We have an Automatic Transfer switch. Normal power is from a breaker in the substation to a service disconnect switch then to a 480 to 480/277 transformer creating a neutral finally it ends up in the ATS for normal power.
We have a E-generator which is 480 / 277 with it's own neutral, all landing in the ATS for E-power.

My question is; in the ATS are the neutrals all tied to a common point in the ATS or should they ISOLATED?

Please see rough sketch attached.

Thanks

 

[iwire]

Is the generator neutral bonded to ground in any other spot other than the transfer switch?

 

[ron]

This is a great presentation covering the topic details.
http://www.russelectric.com/wp-content/uploads/3_or_4_pole.ppt

Bob's question is important, and whether there is ground fault protection at the upstream feeders.

 

[rlundsrud]

neutral

neutral

If the neutral isn't bonded at the generator then yes you can tie them together at the transfer switch. If it is bonded at the generator then you would need a 4 pole transfer switch and isolate the neutral.

Bob

 

[iwire]

If the neutral isn't bonded at the generator then yes you can tie them together at the transfer switch. If it is bonded at the generator then you would need a 4 pole transfer switch and isolate the neutral.

Code wise that is true, however if there is ground fault protection included the use of switched neutral switch is recommended.

 

[rayertz]

Is the generator neutral bonded to ground in any other spot other than the transfer switch?

not sure it is locked out, I will check and let you know.

 

[rayertz]

Code wise that is true, however if there is ground fault protection included the use of switched neutral switch is recommended.

Yes there is GFIC in the substation breaker feeding normal power.

 

[iwire]

Here is another link worth checking http://www.cumminspower.com/www/literature/technicalpapers/PT-7012-ATSselection-en.pdf

But with GFP in place I think a switched neutral with a bond at the generator is a better design.

 

[ATSman]

ATS GF Problems_Solutions

ATS GF Problems_Solutions

This may help