Circuit breaker

A circuit breaker has two thin flat terminals embedded in an electrically insulating housing exposing respective broad flat sides of the terminals in spaced side-by-side relation to each other in a housing chamber. The circuit breaker has a thermostat metal member secured at one end to one exposed side of one terminal to mount the member extending along a chamber wall and has a contact at its opposite end to engage and disengage the other terminal to close and open a circuit in response to a selected current in the circuit. The contact comprises a material which erodes during repeated cycling of the circuit breaker. The thermostat metal member has a portion of reduced cross-sectional area adapted to burn out and separate the member into two sections to open the circuit if the contact welds or sticks to the other terminal. A stop on the housing intercepts movement of one of the member sections after burn out to avoid shorting of the circuit. An abutment on the housing prevents reclosing of the circuit after the contact has eroded to a selected extent. In one embodiment, an electrical resistance heater of positive coefficient of resistivity having an improved electrical wire insulation is wound on the thermostat metal member and retains the circuit in an effective open circuit condition until the heater circuit is separately interrupted to reset the breaker.