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#84399 - 03/25/03 09:05 PM Separately Derived Systems
Carnak Offline
Junior Member
Registered: 03/26/03
Posts: 5
Loc: Grand Cayman
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 do you have to have the 4 pole transfer switch and the separately derived system?
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#84400 - 03/26/03 03:33 AM Re: Separately Derived Systems
russ m Offline
Member
Registered: 02/22/03
Posts: 169
Loc: Burbank,IL,USA
This same question is asked in the General Discussion Area.
Look for a post by wolfdog (backup generators)

Russ
I added this link to it. Just click it
http://electrical-contractor.net/ubb/Forum1/HTML/002728.html

[This message has been edited by russ m (edited 03-26-2003).]
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#84401 - 03/26/03 03:45 AM Re: Separately Derived Systems
russ m Offline
Member
Registered: 02/22/03
Posts: 169
Loc: Burbank,IL,USA
I just went into the search section of this forum (ECN) and typed in transfer switch. There are alot of threads on this subject.

Russ

[This message has been edited by russ m (edited 03-26-2003).]
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