Industrial Control Panel short circuit current rating

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hazlee

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The 2005 NEC of NFPA 70 has added section 409, Industrial Control Panels and identifies the requirement to mark such a panel with the short circuit current rating (SCCR).
Reference to one approved method of calculating it that of Supplement SB of UL 508A.
What I find out is that following the Supplement SB of UL508A results in identifying most panels with a 5ka SCCR vaule.
If you have a panel requireing a 200A service and rating at 5ka SCCR--How can you supply power to this panel?
Anyone have issue with this?
 
Re: Industrial Control Panel short circuit current rating

Unless the panel has been combination tested in the enclosure you may have quite a challenge.
When testing is do the impedance of the fuses of breaker, there contactor, and the OLR all play a part in determining the KAIC of the assembly which also includes the damage that is allowable as well as the enclosures ability to keep the pieces inside the cabinet.
The KAIC rating must be affixed to the enclosure otherwise 5KAIC must be used as a default.
 
Re: Industrial Control Panel short circuit current rating

Your post is regarding Section 409, Industrial Control Panels. How does a 200 amp service panel
enter into this discussion. Check the site below about the middle of the page. It speaks of made up panels with variuous components. Each component has a SCCR rating. The component with the lowest SCCR determines the panel rating.


http://www.ul.com/tca/summer04/qa.html
 
Hello, i am new to the site and have a question about the original post. I work at a oem panel shop and are building a panel with a 200a flange mount disconnect with 3 motor loads: 1@40hp 380/50hz 2@7.5hp 380v/50hz. With a plc and some other small components. How do i determine the sccr value for the panel? Do i use the smallest value component? Example class cc fuse holder rated at 5ka as my sccr value? All help would be greatfull.
 
oem101 said:
Hello, i am new to the site and have a question about the original post. I work at a oem panel shop and are building a panel with a 200a flange mount disconnect with 3 motor loads: 1@40hp 380/50hz 2@7.5hp 380v/50hz. With a plc and some other small components. How do i determine the sccr value for the panel? Do i use the smallest value component? Example class cc fuse holder rated at 5ka as my sccr value? All help would be greatfull.
Click to expand...

how could a clss cc fuse holder only be rated at 5KAIC? Its a 100kAIC fuse???
 
Thanks for not helping. If you read it you would see i was just using a number as an example. I thought this would be a good site for answers, but i see it is the same as most internet sites. Thanks but no thanks.

To all others. I have all the spread sheets showing the combination motor controllers for use in industrial control panels. The components selected are sq'd and rated at 65ka. If i understand correctly the panel has to be rated for the smallest ka device used. There are terminal blocks and other small components with much smaller ka values then 65ka. There seems to be alot of grey areas with sccr and myself as well as others are very confused. Again all help(well some) would be greatful. Thank You Paul
 
It is an interesting dilemma. I think you have to use the intent of the references to help with your interpretation. If you use the most strictest sense of the code, then you will need to gather up all the data on the components that go into your panel. If you want to achieve a higher rating, then it may require you to do a little supplier shopping, and find components that have a least the rating you are looking for. Beyond that, call the local inspector in your area, and have hime help you with the interpreation. Certainly if your shipping the panels all over the country, this may not overcome all obstacles, but at least be a place to start.

As far as help here; you sometimes have to have thick skin. There are many willing to help, but unfortunately there are some that just like to pick apart everything and never really supply an answer. Take everything with a grain of salt.
 
First check out 110.9 and then 110.10

Why? Because SCCR and KAIC are not the same thing.

I'm not the one to try explaining it, but at least make you aware.
 
oem,
Thanks for not helping.
Click to expand...
That was a ligitimate answer to your question. When things in the original question don't look right, many of us will answer the question with another question. If we are not clear on exacty what you are trying to do, there is no way that we can provide an answer.
If you read it you would see i was just using a number as an example.
Click to expand...
There is no way to know that from your original post.
I thought this would be a good site for answers, but i see it is the same as most internet sites.
Click to expand...
It is a great site for answers, but you have to ask a real question.

Don
 
Thanks to all who responded. Our local inspector is schuelded to come in and i wanted to be sure i had all my paperwork completed for him.

Don
There is no way to know that from your original post.
Click to expand...

Oem
Example class cc fuse holder rated at 5ka
Click to expand...

Looks clear to me.

Thanks again.
 
oem,
Example class cc fuse holder rated at 5ka as my sccr value?
Click to expand...
If you read it you would see i was just using a number as an example.
Click to expand...
Looks clear to me.
Click to expand...
It is not clear that the 5ka is just a number used as an example. The example is "class cc fuse holder rated at 5ka as my sccr value". The complete phrase is the example, not just the number.
Don
 
Cooper Bussmann has a SCCR compliance software offer on thier website. It has an annual fee but this may be very helpful in meeting the 508A requirements. The name of the software is OSCAR (online short-circuit current rating software)
 
Blanket fuse tables in 408A SB4.2

Blanket fuse tables in 408A SB4.2

We are having a real issue with using the 408a method to determine our SCCRs. Our problem is that our panels operate heaters using SSRs and run at about 100A in the on state. If you are familiar with table SB4.2 you know that this table is nothing but a major hindrance if youre above 30A. Bottom line is...this table gives all of our panels a 5kA SCCR, when the fact is that high-speed J fuses adequately protect the SSRs based on the manufacturers data. I understand why UL is using blanket ratings, but IMHO it is too restrictive and NEC should exempt industrial heater controls from having to use table SB4.2. A more sensible approach would be to require on-panel LABELLING as to proper and specific fuse replacements and let us use fuse ratings based on reality, not blankets. What do we have to do to get this exception written into NEC 409?
 
Blanket fuse tables in 408A SB4.2

Blanket fuse tables in 408A SB4.2

We are having a real issue with using the 408a method to determine our SCCRs. Our problem is that our panels operate heaters using SSRs and run at about 100A in the on state. If you are familiar with table SB4.2 you know that this table is nothing but a major hindrance if youre above 30A. Bottom line is...this table gives all of our panels a 5kA SCCR, when the fact is that high-speed J fuses adequately protect the SSRs based on the manufacturers data. I understand why UL is using blanket ratings, but IMHO it is too restrictive and NEC should exempt industrial heater controls from having to use table SB4.2. A more sensible approach would be to require on-panel LABELLING as to proper and specific fuse replacements and let us use fuse ratings based on reality, not blankets. What do we have to do to get this exception written into NEC 409?
 
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