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#78608 - 10/06/01 10:26 AM 3ph 200a + 100a + 100a  
Cindy  Offline
Member
Joined: Jun 2001
Posts: 196
PDX, OR, US
I was looking at a prospective job yesterday and was told by the owner that he was told he had to replace everything with a 400a service. Conductor sizes were fine. The arrangement was an overhead fed meter, to a gutter below, a 100a breaker panel on the right, a 100a disconnect on the left to a subpanel, and a 200a disconnect on the left to a subpanel. The owner thinks the issue had to do with this being 3 phase and feeding the 200a panel. Is there enough information here to guess what might be wrong that would require replacing this with a 400a service, CT can... the whole enchilada?


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#78609 - 10/06/01 04:35 PM Re: 3ph 200a + 100a + 100a  
Scott35  Offline

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Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
If the subfeeds / subpanels will have increased loads connected to them [like 50% or more of their maximum capacity], plus the loads will be running at the same time ,along with 3 hours or more [LCL], than this new load calculation might very easilly exceed the existing service capacity.

Is the existing service 200 amps?

If this Client plans to draw high loads and expand in the future, the 400 amp service is a valid concern.
Calc the project out, then figure out what is the best way to go.

Scott SET


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#78610 - 10/07/01 09:54 PM Re: 3ph 200a + 100a + 100a  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
No, there is not enough information.
Please clarify...
WHO told the owner to replace everything?
What do you mean "the conductor sizes look fine"?
Being 3 phase has no significance.
What is the existing load demand?

[This message has been edited by Redsy (edited 10-07-2001).]


#78611 - 10/08/01 11:50 AM Re: 3ph 200a + 100a + 100a  
WARREN1  Offline
Member
Joined: May 2001
Posts: 176
Greenville, SC, USA
Not enough information. And yes, 3 phase will make a difference for phase load balance, which will be of some concern. We try to keep phases balanced within 10% on the connected load schedules.


#78612 - 10/08/01 08:56 PM Re: 3ph 200a + 100a + 100a  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
Warren,
I still don't understand why it being a 3 phase service has any bearing on whether an upgrade is needed. I think the main concern is load calculations. The panel layout may be a matter of convenience.



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