SQD PL Breaker AIR rating

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wbdvt

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Rutland, VT, USA
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Electrical Engineer, PE
A SQD PL breaker has what appears to be 2 AIR ratings: one is 100kA (1ph) the other 14kA (3ph) at 480V. However, the SQD literature only has 100kA listed for this breaker.
Has anyone seen this type rating before? And 14kA seems awful low compared to 100kA rating.
 

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wbdvt said:
A SQD PL breaker has what appears to be 2 AIR ratings: one is 100kA (1ph) the other 14kA (3ph) at 480V. However, the SQD literature only has 100kA listed for this breaker.
Has anyone seen this type rating before? And 14kA seems awful low compared to 100kA rating.
Click to expand...

I think the 100k rating is for 240 V and the 14 k for 480 V.
 
The only way that I can interpret that to make sense is that the first column is for split phase (120-0-120 = 120/240 three wire single phase, and 240-0-240 = 240/480 three wire single phase) and the second column is for a wye or corner ground in which the phase to ground voltages are 240 in top row and 480 in bottom row. Similar to overall slash rating seen on breakers.

But if that is what they mean they sure could have stated it more clearly. Possibly the spec does a better job than the label.
 
wbdvt said:
A SQD PL breaker has what appears to be 2 AIR ratings: one is 100kA (1ph) the other 14kA (3ph) at 480V. However, the SQD literature only has 100kA listed for this breaker.
Has anyone seen this type rating before? And 14kA seems awful low compared to 100kA rating.
Click to expand...

The likely reason for the weird values at single phase is because if you run power through all three poles in series, you get 100kA. But with 3 phase where the circuits are in parallel, it's only 14kA, and now in the new version they just did away with that single phase rating. When you get something UL listed, or probably in this case RE-LISTED after a design change, testing is very expensive. So if no customer (or too few) ever used these breakers for single phase, someone probably made the decision to not bother paying for that testing again.
 
NEC 240.85 may help...

“A two-pole circuit breaker shall not be used for protecting a 3-phase, corner-grounded delta circuit unless the circuit breaker is marked 1φ–3φ to indicate such suitability.”


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mach531 said:
NEC 240.85 may help...

“A two-pole circuit breaker shall not be used for protecting a 3-phase, corner-grounded delta circuit unless the circuit breaker is marked 1φ–3φ to indicate such suitability.”


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Click to expand...
A good find on the meaning of the graphic on the label. FWIW the breaker pictured is three pole.

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