Is a PK2MB retaining bracket required for use in a QO2100BNS enclosure if used as a main breaker?
QO Circuit Breaker Enclosures
No the PK2MB retaining bracket, is not required. The incoming conductor are connected to the lugs of the mounting base. If the 2 pole breaker is removed from the base, the breaker load lugs will not be energized(or hot).