1. A circuit breaker comprising an electrically insulating housing and including a box-like container and a cover therefor, a circuit breaker structure within the housing and comprising a pair of separable contacts operable between open and closed positions, a releasable member in an initial position and movable when released to a tripped position to effect automatic opening of the contacts and comprising an elOngated current-carrying bimetal for tripping the releasable member when a predetermined current overload effect deflection of said bimetal in one direction from a latched position, the bimetal being mounted at one end portion and disposed in an unbiased position, bimetal stop means for preventing said bimetal from moving in the other direction from said latched position when the bimetal is subjected to extremely cold ambien temperature, and the container and the cover being molded members one of which comprises an integral molded projection at the other end of the bimetal.

2. A ground fault circuit interrupter for use in a load center and comprising a circuit breaker, a ground fault detector, and an insulation housing therefor; the circuit breaker comprising a pair of cooperable contacts operable between open and closed positions, a releasable member in an initial position and movable when released to a tripped position to effect automatic opening of the contacts, an elongated current-carrying bimetal element for tripping the releasable member when a predetermined current overload effects deflection of said bimetal element in one direction from a latched position, the bimetal being mounted at one end portion and disposed in an unbiased position, bimetal stop means for preventing said bimetal element from moving in the other direction from said latched position when the bimetal is subjected to extremely cold ambient temperature; the ground fault detector comprising a current monitoring core, a plurality of primary windings on the core, each being one of a line and a neutral conductor of an A.C., electrical distribution system, a secondary winding sensing current imbalance between the primary windings, means responsive to a predetermined sensing signal to open said line conductors, the means responsive to a predetermined sensing signal including a pivotally movable member movable against said bimetal element to unlatch the releasable member, and the pivotally movable member being adjacent to the bimetal element on the side of the bimetal stop means.