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#72670 - 12/06/06 06:51 PM Fault Current
nwelectric Offline
Junior Member
Registered: 06/09/05
Posts: 4
Loc: hiram, ga.
We have bid a condo project with a 600a single phase meter main on each bldg with 3 200a breakers feeding 3 condos per bldg and 1 100a breaker for a house panel. The meter main is spec to have a 600a MCB. The engineer says Isc at 37,191 at service with Isc 29,246 worst case at the apartment panels. I bid using Square D components in meter main at 44k aic. If I use mcb and each 200a at 44k aic shouldn't I be good to use 10K panels (again spec as MCB panels) in the units. I would have 44k and another 44k in series. What do you think???

NW
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#72671 - 12/06/06 07:22 PM Re: Fault Current
Dave T Offline
Member
Registered: 01/22/05
Posts: 155
Loc: Waukesha, WI, USA
Are the OCPDs series rated?
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#72672 - 12/06/06 07:43 PM Re: Fault Current
nwelectric Offline
Junior Member
Registered: 06/09/05
Posts: 4
Loc: hiram, ga.
Waiting on Sq D to answer that based on their bid for service.
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#72673 - 12/06/06 08:39 PM Re: Fault Current
Bob Offline
Member
Registered: 02/05/02
Posts: 182
Loc: Mobile, AL, USA
nw
Can you give me an estimate of cost difference for the 2 options for breakers? Just curious.

[This message has been edited by Bob (edited 12-06-2006).]
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#72674 - 12/07/06 12:11 AM Re: Fault Current
e57 Offline
Member
Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
Most of the breaker companies have that info for series rating on-line - but are often hard to find...
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#72675 - 12/07/06 07:31 AM Re: Fault Current
JBD Offline
Member
Registered: 07/12/01
Posts: 599
Loc: WI, USA
Square D has a listing of their series ratings in their Digest (pages 2-8 and 2-9).

In general you can not apply three devices in series and still have a series rated system. You may have to change each apartment to a main lug only style.

Is this a single 600A main breaker and meter feeding seperately mounted breakers which then feed the individual apartments? Or, is it a 600A main feeding a meter center with individual combination meter sockets for each circuit (Square D type MP or EZM) which then feed each apartment?
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#72676 - 12/07/06 09:20 AM Re: Fault Current
Jps1006 Offline
Member
Registered: 01/22/04
Posts: 615
Loc: Northern IL
Quote:
In general you can not apply three devices in series and still have a series rated system. You may have to change each apartment to a main lug only style.


Well that kind of defies common sense. If it's series rated with two, wouldn't more be better? Is there an electro-mechanical reason to this or is it just because it hasn't been tested this way for the listing?
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#72677 - 12/07/06 10:19 AM Re: Fault Current
RODALCO Offline
Member
Registered: 12/08/05
Posts: 854
Loc: Titirangi, Akld, New Zealand
Single Phase 600 Amps !!

Don't they share the load over three phases and bring 1Ø, 100 Amp services into the individual appartments ?
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#72678 - 12/07/06 11:54 AM Re: Fault Current
JBD Offline
Member
Registered: 07/12/01
Posts: 599
Loc: WI, USA
Quote:
Well that kind of defies common sense. If it's series rated with two, wouldn't more be better? Is there an electro-mechanical reason to this or is it just because it hasn't been tested this way for the listing?


It all has to do with dynamic impedance of the devices opening as well as the static impedance of the circuit. Because of this devices must be tested in series.

Square D does have three tier ratings for use with their multi-metering devices.
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