Trip-free high limit control

摘要

A trip-free high limit control for a water heater having a source of heat to heat the water. A switch arm is mounted in a control housing for movement in the housing. The switch arm has a first contact portion at one end thereof. A second stationary contact is mounted in the housing. The contact portion on the switch arm is movable relative to the stationary contact between closed and open positions to control the energization and de-energization of the source of heat for the water heater. A bi-metallic snap disk is mounted in the housing and is movable with snap action between first and second positions of stability at a predetermined overheat temperature. A switch arm actuating plunger is mounted in the housing for movement by the snap disk to open the switch contacts at a predetermined overheat temperature. A reset mechanism is provided which includes a reset spring mounted in the housing in operable engagement with the plunger. The spring is calibrated to provide a predetermined force on the plunger relative to a predetermined compression travel force exerted on the spring. The reset mechanism further includes a reset button in operable engagement with the reset spring. The housing has a stop surface therein to limit travel of the reset button. Such limited travel of the reset button will limit the force applied to the plunger by the compression of the spring which, in turn, will limit the reset force applied to the bi-metallic snap disk. The reset mechanism will thus operate to produce insufficient force on the bi-metallic snap disk until a predetermined safe operating temperature is sensed by the bi-metallic snap disk. As a result, the operation of the water heater cannot be resumed after the bi-metallic disk is snapped at the overheat temperature until a safe operating condition is restored in the water heater.