Short Circuit Current Ratings, NEC2005-Art 409

[EvanH]

Trying to get familiar with the new requirements for industrial control panels, particularly the necessity to mark the panel with a "Short Circuit Current Rating".
It's my understanding that (since our panels are not individually listed as an assembly), the components in the power distribution path (not control circuit components) must each have a SCCR value, and you take the smallest one as the SCCR of the panel. Can anyone out there confirm this understanding? (And just curious whether people are really doing this yet, since I've never seen a panel or component marked with this).

Also, I have these two questions:
1)Do we need to consider devices such as motors and heaters that are fed by the controls in the panel, or only devices mounted within the panel itself?
2)When using a 240/120VAC single phase 3-wire (2 hot and 1 neutral) power source, can I still ignore my "control circuit" components, which in this case are wired between a hot leg and neutral, rather than between two hot legs?

Thanks for any input,
Evan

 

[RonShap]

Considering the text below, it seems that you need a UL listing as an assembly with an associated short circuit test for the assembly, or some other mysterious "approved method" from UL.


409.110 Marking.
An industrial control panel shall be marked with the following information that is plainly visible after installation:
(3) Short-circuit current rating of the industrial control panel based on one of the following:
a. Short-circuit current rating of a listed and labeled assembly
b. Short-circuit current rating established utilizing an approved method
FPN: UL 508A-2001, Supplement SB, is an example of an approved method.

 

[dbaird]

There seems to be much confusion on this. We are located in Dayton,OH and Schneider Electric is going to put on a seminar, through Northwest Controls, to try and educate machine builders on this. It will be sometime in Sept. of this year. In the meantime you can go to their website and view a presentation on the topic:

http://www.squared.com/us/products/...B03C85256EBE0047F560/$file/ul508aFrameset.htm

David Baird
mrbaird@hotmail.com
Sr Controls Engineer
EET degree.
Journeyman Electrician.

 

[jonesy29847]

Issue 1, January 1, 2005 Plant Engineering magazine has a very good article on SCCR.

We added it to our standards, and the tag must list the lowest SCCR contained within the enclosure.

Hope this helps.

 

[rbulsara]

Regardless of what component you use and the technical analysis, if you want to apply a label on an assembly, it must be approved/tested by some nationally recognized testing lab (NRTL) such as UL or ETL etc. You need to go through the procedures set out by those testing labs as Ronshap precisely indicated.

In many cases, UL will in fact test the equipment for the SCCR the mfr. claims it to be.