Unlabled MCC Short Circuit Rating

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mtevebaugh

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I am attempting to design a system upgrade around a 50+ year old MCC that does not have a nameplate on it. Is there any sort of standard that defines a safe assumption for what the short circuit rating is?

If not, is it even possible to field test for a short circuit rating? This seems like it would be a destructive test.
 
Officially, the maximum SCCR (Short Circuit Current Rating) can be considered to be 5kA without testing, but that isn't going to help much. For someone such as a PE to officially give you anything better, he would need to show evaluations of each and every sub-system inside that MCC, i.e. each and every starter bucket, feeder CB, main CB etc. If ANY ONE of them is un-determinable, it becomes 5kA by default and therefore the entire lineup rating becomes that of the lowest rated unit.
 
mtevebaugh said:
I am attempting to design a system upgrade around a 50+ year old MCC that does not have a nameplate on it. Is there any sort of standard that defines a safe assumption for what the short circuit rating is?

If not, is it even possible to field test for a short circuit rating? This seems like it would be a destructive test.
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A 50yr old MCC has long ago reached the end of it's useful life. I would not bother worrying about what it is rated; simply replace it with new appropriately rated equipment.
 
Thanks

Thanks

Thanks Jraef.

And king I definately agree. We tried to go that route to begin with but the client wouldn't pay for it. I'm hoping the fact that we have to default to 5kA might push them a little closer to replacing it. *fingers crossed*
 
mtevebaugh said:
I am attempting to design a system upgrade around a 50+ year old MCC that does not have a nameplate on it. Is there any sort of standard that defines a safe assumption for what the short circuit rating is?

If not, is it even possible to field test for a short circuit rating? This seems like it would be a destructive test.
Click to expand...


oh, Still you want to use that. you might think ,

Old is gold.
 
mtevebaugh said:
I am attempting to design a system upgrade around a 50+ year old MCC that does not have a nameplate on it. Is there any sort of standard that defines a safe assumption for what the short circuit rating is?

If not, is it even possible to field test for a short circuit rating? This seems like it would be a destructive test.
Click to expand...
UL did not begin putting SCCR labels on equipment like MCC's until the early 80's, prior to that equipment may have had 'self-certified' lables if anything.

With MCC's you may have a bus bar bracing level (I remember when 22K was fairly standard) and a different rating for the buckets.

I vote for calling it 5KA.
 
mtevebaugh said:
I am attempting to design a system upgrade around a 50+ year old MCC that does not have a nameplate on it. Is there any sort of standard that defines a safe assumption for what the short circuit rating is?

If not, is it even possible to field test for a short circuit rating? This seems like it would be a destructive test.
Click to expand...


In thesedays, I have seen some catalog for MCC. till 60 Amp breaker usually has 6kA. As the size of breaker increases the kA also in raises.

like
60 ampere has 6kA
100 ampere has 10kA


Like legrand catalog.
 
jim dungar said:
UL did not begin putting SCCR labels on equipment like MCC's until the early 80's, prior to that equipment may have had 'self-certified' lables if anything.

With MCC's you may have a bus bar bracing level (I remember when 22K was fairly standard) and a different rating for the buckets.

I vote for calling it 5KA.
Click to expand...

I third it, call it 5k, tear it out and replace with new. I may be able to get you some credit for your old buckets.
 
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