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back up generator #23732
03/25/03 10:01 PM
03/25/03 10:01 PM
W
wolfdog  Offline OP
Member
Joined: Oct 2001
Posts: 135
Dallas,TX
This question was asked of me at another web site and I don't have a good answer. Would you folks enlighten me so I can pass it on.

Consider a commercial building with a three phase service and 100% generator back up.

If you use a 3 pole transfer switch, you don't break the neutral.

If you use a 4 pole switch, you break the neutral, add some extra grounding, and the system is now "Separately Derived".

When in your opinion do you have to have the 4 pole transfer switch and the separately derived system?

I would like your opinion on tapping service feeders also.





[This message has been edited by wolfdog (edited 03-25-2003).]

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Re: back up generator #23733
03/25/03 11:05 PM
03/25/03 11:05 PM
R
russ m  Offline
Member
Joined: Feb 2003
Posts: 169
Burbank,IL,USA
Try these links.
http://www.mikeholt.com/cgi-bin/codeforum/ultimatebb.cgi?ubb=get_topic;f=18;t=005123
http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=18;t=005233#000000

Re: back up generator #23734
03/26/03 12:26 AM
03/26/03 12:26 AM
N
Nick  Offline
Member
Joined: Aug 2001
Posts: 599
Riverside, CA
Short answer: When ground fault protection is required on either the service entrance or generator or both.

Re: back up generator #23735
03/26/03 07:44 AM
03/26/03 07:44 AM
W
wolfdog  Offline OP
Member
Joined: Oct 2001
Posts: 135
Dallas,TX
Thanks for the responses and links.

Obviously, I have not been keeping up very well with the Mike Holt forum.


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