In the NEC I can find where it discusses breakers must be loaded to 80% of their capacity and the conductors must be sized at 125% of the load (or the rating of the breaker). So a 1200-amp breaker can only be loaded to 960-amps and your conductors have to be rated for 1200-amp. NEC also discusses variations if it is continuous or non-continuous loads. If I have continuous loads the ratings above apply, If I have non-continuous loads and a 100% rated breaker can the breaker be loaded to 100%? Would you be required to size your conductors at more than 1200-amp?
80% vs 100% Breaker Rating and Continuous vs Non-Continuous loads
- Thread starter dcheser
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- New Jersey
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- Journeyman Electrician (retired)
Standard circuit breakers are rated for 80% continuous load (or continuous load*125%) or 100% non-continuous load or a combination of both. A 100% circuit breaker is rated for 100% continuous load, the difference between the two is that he 100% CB will be designed to compensate for the more heat generated with the 100% load. Take a look at 210.19(A).
electrofelon
Senior Member
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- Cherry Valley NY, Seattle, WA
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- Electrician
And to add to that, it's the enclosure also that needs to be approved and coordinated with the 100% breaker. You can't just take a 100% breaker and throw it in any panel board and use at 100% continuous.
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- New Jersey
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- Journeyman Electrician (retired)
Yes that's correct, I should have mentioned that in the section I posted the exception states just that, that the assembly as well as the CB need to be listed for 100% operation.
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