Issue:
Is it OK to use an 80% rated breaker at 100% if set to less than 80% of its max. rating?
Product Line:
Circuit Breakers
Resolution:
No, the breaker is not labeled for 100% and doing so would be a violation of its UL listing
This question is not addressed directly in the NEC or UL, but it is addressed by the application statements and guidelines for standard and 100% rated breakers. They do not allow 100% application for any breakers but those so marked. For reference, please see the attachment and NEC 210.20(A) and NEC 215.3.
Note that 100% marking is required only for continuous application at over 80% of the breaker rating (3 hours or more). Shorter periods of operation up to 100% of the breakers rating are allowed.
Example:
A standard rated 600A Powerpact L frame breaker (not labeled for 100%) set at 400A (less than 80% of 600A) could NOT be applied as if it were rated for 100%.
Set at 400A, this breaker would have a maximum continuous current rating of 400 x 80% = 320A.
Is it OK to use an 80% rated breaker at 100% if set to less than 80% of its max. rating?
Product Line:
Circuit Breakers
Resolution:
No, the breaker is not labeled for 100% and doing so would be a violation of its UL listing
This question is not addressed directly in the NEC or UL, but it is addressed by the application statements and guidelines for standard and 100% rated breakers. They do not allow 100% application for any breakers but those so marked. For reference, please see the attachment and NEC 210.20(A) and NEC 215.3.
Note that 100% marking is required only for continuous application at over 80% of the breaker rating (3 hours or more). Shorter periods of operation up to 100% of the breakers rating are allowed.
Example:
A standard rated 600A Powerpact L frame breaker (not labeled for 100%) set at 400A (less than 80% of 600A) could NOT be applied as if it were rated for 100%.
Set at 400A, this breaker would have a maximum continuous current rating of 400 x 80% = 320A.
Released for:Schneider Electric USA
