Abstract: A normally open thermal switch (200) having a bimetallic disk (18) is configured for operational testing in its installed position when exposed to a changing temperature by a test box (400) having a power source (400a). The in-place testing advantageously confirms triggering action of the switch by an event indicator (400c) at the operational temperatures designed into the switch (200). The temperature of the triggering action is presented on a temperature display (400b) and recorded by a data recorder (400d) of the test box (400). The switch (200) incorporates a heating element (24c) to heat changing the bimetallic disk (18) to snap activate at the operative temperatures. The thermal switch (200) is coupled with the test box (400) to confirm its operation without having to remove the switch from its installed location.

Abstract: An integral resistance element combined with a snap-action thermal switch and coupled to an output thereof, the snap-action thermal switch being structured in a normally-open configuration. The resistance element and the snap-action thermal switch share one or more common terminals. The snap-action thermal switch is structured having a pair of terminals being mutually electrically isolated when the snap-action thermal switch structured in the normally open configuration, and the integral resistance element is electrically coupled to provide an output on the pair of electrically isolated terminals.