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What is the maximum size sub-feed circuit breaker for an NQ NEMA 3R/5/12 panelboard?

Issue:
What is the maximum size sub-feed breaker that can be used in an NQ NEMA 3R rated panelboard?

Product Line:
NQ panelboards, NEMA 3R/5/12 enclosures

Environment:
Panelboards

Cause:
Installing larger amperage sub-feed breakers in NEMA 3R/5/12 NQ panelboards

Resolution:
The maximum size sub-feed breaker for a NQ panelboard in a NEMA 3R/5/12 enlcosure 150A. If a twin sub-feed breaker kit is used, such as NQSFB4Q or NQSFB4HJ, each position is restricted to 150A. This is true for all amperages and sizes of NQ panelboards in NEMA 3R/5/12 enclosures, due to heat rise testing. 
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