Series Rating, different breaker, same TCC

Status
Not open for further replies.
N

NukePNW

Member
Location
Oregon
Occupation
PSE
Long time reader, first time poster.

I'm currently doing a short-circuit study at a location. We have a combination where the upstream breaker is rated 100 kAIC and the downstream breaker is rated 22 kAIC with ~58 kA of fault current. Luckily, that combination is series rated to 100 kAIC so we were good to go (consultant is fine with series rating). However, the plant didn't have the 100 kA breaker on hand, so they swapped in the 200 kA version. Same frame, same trip unit, same TCC... but, the 200 kAIC hasn't been tested with the 22 kAIC breaker. So, I'm losing my series rating.

I think I read somewhere that if you have a tested, series rated combination, that test can be applied to other breakers that share the same TCC even if they are not the exact same breaker. But, I can't find the standard now. Does this sound familiar to anyone? It makes common sense to me, but I need to find a specific reference for the inspector.

Thanks!!!!
 
Never mind... I found the standard I was thinking of. It's a Kohler white paper that allows you to use a different type of breaker wiht the same TCC to stand in for a breaker on their specific breaker list. Doesn't help me here.

But, thanks for reading!
 
I do not think you would find that in the NEC. The NEC allows series rating, but I believe it leaves the actual test definition to UL or other standards.
I have always thought that the series rating list applies only to the exact models which were tested, with no leeway for substitution, but I have not seen the relevant source documents.
 
GoldDigger said:
I do not think you would find that in the NEC. The NEC allows series rating, but I believe it leaves the actual test definition to UL or other standards.
I have always thought that the series rating list applies only to the exact models which were tested, with no leeway for substitution, but I have not seen the relevant source documents.
Click to expand...

The listed series combination must have been tested by UL using the actual breakers, so substitution is not allowed.
 
And to be clear, the TCC and the IC rating are not related. The IC rating has to do mostly with physical construction, not the tripping aspect.

Series rating have to do with the tripping and fault clearing times. So yes, technically IF it were allowed, the TCC would be relevant to the series rating aspect, not the IC rating, but as pointed out it is not allowed. Only SPECIFIC units as tested are allowed to have a series rating.
 
Jraef said:
And to be clear, the TCC and the IC rating are not related. The IC rating has to do mostly with physical construction, not the tripping aspect.

Series rating have to do with the tripping and fault clearing times. So yes, technically IF it were allowed, the TCC would be relevant to the series rating ...
Click to expand...

Series rated breakers open and clear at times faster than the 0.01sec shown on TCCs. The same thing applies to fuses operating in their current limiting region.

TCCs are usually only applicable to relatively slow coordination situations.
 
Status
Not open for further replies.
Top