Recessed lighting fixture and an insulation detecting protector device

Abstract

An electrical lighting fixture adapted for recessed mounting has structure for mounting and energizing a lamp and has an insulation detecting protector device adapted to interrupt operation of the lamp to prevent overheating of the fixture if thermal insulation is disposed around the fixture in such a way as to excessively block heat dissipation from the fixture. The protector device has structure for mounting the device on the fixture to be subject to representative fixture conditions, has a thermally responsive switch which is actuatable in response to heating to a selected temperature for interrupting operation of the lamp, and has an electrical resistance heater which is thermally coupled to the switch for actuating the switch if thermal insulation excessively blocks dissipation of heat from the protector device. Thermal barrier elements are incorporated in the leads which connect the switch and heater to a power source and to the lamp and limit heat-transfer out of the protector device via the leads to a minor proportion of the heat output of the heater, thereby to permit operation of the heater at a low power level while assuring that the protector device prevents overheating of the fixture and avoids nuisance interruption of the lamp even during anticipated levels of variation in line voltage and ambient temperature.