Determining SCCR for an Industrial Panel

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Machiavelli999

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I am trying to figure out the SCCR for a new industrial panel my client put in. I have never actually done this before an it seems that this would be a job for a third party inspector, but regardless it fell on me.

I know that the panel has a main internal fuse with an interrupting rating of 200kA. Is that sufficient to label the panel as 200kA for its SCCR?

I found this document from Cooper Bussman and its rather confusing: http://www.cooperindustries.com/con..._Rating_Calculations_and_Marking_2008_SPD.pdf

It talks about a "Two Sweep Method" which seems to involve evaluating the SCCR of each and every component in the panel. Is that what will be necessary? Anyone know?
 
Machiavelli999 said:
It talks about a "Two Sweep Method" which seems to involve evaluating the SCCR of each and every component in the panel. Is that what will be necessary? Anyone know?
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Basically, the component with the lowest rating is going to determine your SCCR.

I am not sure what you do if you have unrated components. UL has a chart in their procedure for how to handle components that do not have an SCCR rating but I don't know that you can use the UL procedure outside of a UL listed panel, and if it was a UL listed panel it would say what the SCCR is on the panel nameplate.
 
NEC 409.110 and UL NITW for "Industrial Control Panels" require a nameplate showing the SCCR.
If your customer is the end user and not the supplier, my approach would be to ask the supplier for that required information.
 
Here is how we do it

Here is how we do it

We are a UL panel shop. We build panels and determine their SCCR all the time. UL 508A supplement SB4 is what we use. There may be and probably are other approved methods available but we do not know of any other than UL 508A SB4. I can't tell you in a short e-mail how this is done but i will state this:

1. For "unmarked" components: the table in UL 508A supplement SB4 can only be used for UL listed components (this was from a clarification from UL). If it has no rating and it is not UL listed, the table cannot be used and most likely you will not be able to achieve any rating for your panel if you choose to use that component. We cannot put a UL sticker on one of our panels if any of the components are not UL listed. You can't just slap 5k on a panel to get around determining the actual rating.
2. The rating of the panel is not always limited by the rating of the lowest rated device. There are methods outlined in UL 508A supplement SB4 which can be used to "improve" a low rated device.
3. The info provided by Bussmann is very good and very useful
4. Not all components in a panel are required to be evaluated: only those components in power circuits. see SB4.1.1
5. Not all power circuit components are required to be evaluated (e.g. reactors, CTs, caps, resistors) see SB4.2.1
6. Under some conditions, the SCCR rating cannot be determined if you do not first know what the available fault current is. see table SB4.2

Hope this helps a little.
 
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