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#210192 - 06/02/13 04:38 PM Elevator SCCR  
cgw  Offline
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Joined: Jul 2004
Posts: 133
Rochester NY
In a typical relatively small building, the elevator is fed from a main panelboard and is usually close. The elevator manufacturer requires a max. 10KA SCCA at the elevator equipment. How do you limit the SCCA at the elevator?


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#210196 - 06/02/13 06:58 PM Re: Elevator SCCR [Re: cgw]  
HotLine1  Offline


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Do you know what the AIC is at the main panelboard??


John

#210197 - 06/02/13 07:18 PM Re: Elevator SCCR [Re: cgw]  
renosteinke  Offline
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You limit the SCCA by having "selective coordination" in your fuse /breaker selections.Simply put, the upstream overcurrent device is sized according to its' response curve, so it will trip before the short circuit draws 10,000 amps.

Usually, this means the appropriate fuse in your disconnect. Your Bussman rep can steer you to the right fuse - and the Bussman site has plenty of stuff to read on the topic


#210198 - 06/02/13 08:11 PM Re: Elevator SCCR [Re: HotLine1]  
JBD  Offline
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Posts: 599
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Originally Posted by HotLine1
Do you know what the AIC is at the main panelboard??
The AIC is not important.

You need to know the SCA, short circuit amps which are available.


#210199 - 06/02/13 08:45 PM Re: Elevator SCCR [Re: renosteinke]  
JBD  Offline
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Originally Posted by renosteinke
You limit the SCCA by having "selective coordination" in your fuse /breaker selections.Simply put, the upstream overcurrent device is sized according to its' response curve, so it will trip before the short circuit draws 10,000 amps.

Usually, this means the appropriate fuse in your disconnect. Your Bussman rep can steer you to the right fuse - and the Bussman site has plenty of stuff to read on the topic



No.
Selective coordination has nothing to do with fault current reduction. It has to do with which device opens in which sequence.

Fault current reduction requires the upstream device must limit its let through current as well as its peak current. Simply choosing a target value, like 10,000A, is not sufficient. At a minimum you still need to know the available fault current. This is why UL, and to a major extent the NEC, requires testing of all series-combinations of protective devices.

Bussmann's SPD (2009 page 77) has information on the use of current limiting fuse Let-Through charts. Protection of equipment (e.g. control panels) has a separate section, which deals with using umbrella fuse let through charts.



#210200 - 06/02/13 08:58 PM Re: Elevator SCCR [Re: cgw]  
HotLine1  Offline


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JBD:

Terminology mistake on my end.

Yes, Bussmann is the site of choice.



John

#210202 - 06/02/13 09:56 PM Re: Elevator SCCR [Re: cgw]  
renosteinke  Offline
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If we "need" to know available fault current .... have you tried doing any 'arc-fault' calculations?

The question matters, because you ultimately arrive at PoCo equipment,and you wind up assuming infinite current available.

So, the switchgear has the first role in defining your available short circuit current. Add some wire length, and the next breaker in the system now has a defined short circuit current - regardless of the PoCo supply.

Sure sounds to me like something you have to do as the first step in a selective coordination study. There you go, off to look at the same response curves.

In truth, what I think the manufacture is telling the OP is that his gear has bussbars that are rated only to 10KA. If so, these ratings may be misleading. I seem to recall (from testing lab experience) that the industry practice is to mount everything to 25KA standards, for their own manufacturing convenience; the 10KA marking is often pure fiction. A chat with the gear maker might clear up this point.

Don't overlook the role of the feeder wires in limiting SCCA. While you're talking to Bussmann, you might want to ask them why they do their testing with 12" leads smile


#210204 - 06/03/13 11:24 AM Re: Elevator SCCR [Re: renosteinke]  
cgw  Offline
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Joined: Jul 2004
Posts: 133
Rochester NY
Originally Posted by renosteinke

Don't overlook the role of the feeder wires in limiting SCCA.


That's the question. Is there a way to limit the SCCA at the elevator equipment without running the feeder a hundred feet down the hallway and back?

(I'll ask Bussman)


#210210 - 06/03/13 02:18 PM Re: Elevator SCCR [Re: cgw]  
HotLine1  Offline


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Joined: Apr 2002
Posts: 6,878
Brick, NJ USA
Yes, you could reduce by the length/size of the feeder.
You still need the available fault current at the source of this feeder for a starting value.



John

#210211 - 06/03/13 02:47 PM Re: Elevator SCCR [Re: cgw]  
cgw  Offline
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Joined: Jul 2004
Posts: 133
Rochester NY
Bussman says the fuse will limit the current.


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