How should you determine the KA Rating of a control panel 1

[snoogie]

When adding a name plate to a control panel with the voltage / current rating etc.. How should the KA of the PANEL be rated for the name plate (ie NOT how is the ka of the supply deterimined). Should it be based on the lowest KA rated device that is connected directly to the incomming supply such as the smallest rated branch circuit fuse or should it be based on the main incomming isolator /breaker fuse KA.

 

[DanDel]

The Interrupting and/or Momentary fault current rating of a device or switchgear assembly is typically found by testing.
In your case, a panel with controls only may be protected to the rating of the main device(fused switch or C/B) if that device is current limiting. Most manufacturers have a 'Series-Rated' manual which lists how an upstream current-limiting device of their manufacture will increase the fault current capability of other downstream interrupting devices.
I would not recommend that you include a fault current rating on your nameplate unless you have proven test results.

 

[jraef]

Nothing wrong with DanDel's answer, but I will add one side issue. If you are referring to the UL nameplate requirements, I believe the only KA rating that you can apply WITHOUT TESTING is 5KA, maybe 10. It's been a while since I opened a UL panel shop, but the definite answer is in your UL 508 proceedures. UL refers to it (or at least used to) as a "courtesy rating".

The testing requirements for anything higher mean essentially blowing up a panel, something that is not worth it for one-off jobs. You build an identical panel, pack it with cotton, subject it to a 25KA fault and see if any of the cotton burns. If not, you apply a higher fault etc. etc. When the cotton burns, your max fault rating is the previous level.

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[snoogie]

You know i think you are right I have had the CSA come and sticker panels here in the past and looking back at the report sheets they all have 5KA as the rating and i could never figure out why everything was 5KA !

Thanks guys i think the only practical answer is to leave it off.

Snoogie

 

[jraef]

With UL508 we were required to list it on the label. Leaving it blank was considered a violation. Being that they generally follow the same rules I would suspect that CSA may be that way as well.

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