Short circuit current for control panels 2

[AAEDSN]

We build control panels for machines. Can I say that the SCCR for the built panel is 5KA without doing the calculations? I think the minimum SCCR is 5KA; is that correct?

 

[Gr8blu]

The short circuit current rating (SCCR) for a panel is the same as the component inside the panel that has the lowest rating - essentially, the "weakest link".

Converting energy to motion for more than half a century

 

[che12345]

"...We build control panels for machines. Can I say that the SCCR for the built panel is 5KA without doing the calculations? I think the minimum SCCR is 5KA; is that correct?"
I have the following opinion. Let us have more advice from others, on this subject.
1. I assumed "panels for machines" are rated per IEC 1ph 230V say < 6.3A. Incoming is protected with a double-pole 10kA MCB rate <6.3A or fused only on the Line conductor. In this case, any short-circuit in it would NOT exceed 5kApeck. Therefore claiming rated SCCR 5kA is valid.
2. Per IEC 60439-1 " verification of the short-circuit withstand strength is not require...." , see more detail etc....
3. WARNING: with the above assumption, the panel would NOT be suitable for locations with SCCR >10kA.
Che Kuan Yau (Singapore)

 

[AAEDSN]

Thank you.

 

[resqcapt19]

What type of machines do you build panels for? In what type of occupancies are they typically installed in? You are doing your customers a huge disservice if your panels are typically install in occupancies that would be expect to have an available fault current exceeding 5 kA. The cost to reduce the electrical circuit fault current will almost always far exceed the cost of building the panel with a higher SCCR.

 

[AAEDSN]

It was just a general question. Thanks for the clarifications.

 

[che12345]

@ Mr Gr8blu (Electrical)17 Jun 24 19:56
"...The short circuit current rating (SCCR) for a panel is the same as the component inside the panel that has the lowest rating - essentially, the "weakest link" ".
I have different opinion. Please advise.
1. The short circuit current rating (SCCR) for a panel is dependent on the incoming protection device (fuse or CB), NOT the component inside it that has the lowest rating.
2. If incoming is protected by say 10kA MCB rate <6.3A or fused only on the Line conductor. In this case, any short-circuit in it would NOT exceed 5kApeck. Therefore claiming rated SCCR 5kA is valid.. On the other hand, with the same 10kA MCB but rated 63A, the SC current peck would > 5kA. Therefore claiming rated SCCR 5kA is NOT valid.
3. A rated 5kA panel can be installed with any lower than rated say 1kA components if it is protected by its own protective device. The panel is still rated 5kA and has nothing to do with the rated 1kA component, which has its own protection.
Che Kuan Yau (Singapore)

 

[davidbeach]

Well, Mr. Yau, that's not how the code works. The incoming fault current matters, but no upstream device matters what so ever. Panel has to work, at its listed rating, on any circuit that can supply that fault current or less. Period. Full stop. If in North American, the OP should probably have said "We build unlisted control panels for machines."

Unlisted - that's generally the end of the discussion.

When one this sentence into the German to translate wanted, would one the fact exploit, that the word order and the punctuation already with the German conventions agree.

-- Douglas Hofstadter, Jan 1982

 

[che12345]

"..If in North American, the OP should probably have said "We build unlisted control panels for machines." Unlisted - that's generally the end of the discussion".
I have the following opinion.
1. It is fine to state "We build unlisted control panels for machines." This means that the panel is NOT intended for installation in the US or Canada, where UL listed/certified industrial control panel (ICP) is mandatory; in the view of the inspector. Note: an unlisted is understood to be NOT tested/certified by UL or the panel is NOT fabricated by an UL certified OEM.
2. Suggestion: ICPs can have endless of variations in the component selection/combination and layout size/IP rating etc... It may be more economical to work with an UL certified OEM, who can ensure that their product will be answerable any issues raised by the inspector.
3. If the ICP is for the US or Canada market, refer UL 508 and UL 508A for more information.
Che Kuan Yau (Singapore)

 

[LionelHutz]

In North America, for the most part if you use the correct power components then the complete panel will be at least 5kA rated. No calculations are necessary but you need to take some care to ensure you get the right parts. You can't just slap in any old parts you buy and call the panel 5kA and be correct.

I have different opinion. Please advise.

Your opinion is wrong. Your complete post is wrong and doesn't apply to North American control panels where SCCR is used. Just don't answer if you don't know, and you've proven you don't know. It would serve the others reading best to just completely disregard all your posts on this subject.

 

[jraef]

As mentioned, yes you can (for the most part) apply an SCCR label at 5kA to a panel without testing or much effort in component selection. But also as mentioned, that 5kA value is all but useless in the real world. I keep repeatedly dealing with this exact issue from what I call “lazy” suppliers of equipment. It takes a VERY LITTLE effort to investigate and coordinate component selection to attain MUCH HIGHER levels of “series” SCCR listing. It will likely require that the major power components be if the same manufacturer, because they are the only ones who will pay the cost of the series testing, but that’s a small price to pay for attaining a more useful SCCR value for the people that have to live with it in the field.


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