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When can you use UL 1077 vs. UL 489 breakers in panels or equipment?

The general rule is that you can use UL 1077 supplementary protectors to protect all circuits inside the equipment EXCEPT FOR those that feed motors or transformers and those that exit the equipment which would be classified as branch circuits or could be used for outlets or for feeding utilization equipment. Supplementary protectors can be used where UL 489 (branch circuit) protection is not required or is provided by another device.


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