Robust design and high grade materials meet the stringent demands of today's service professional. In design, we specify custom wax formulations that will expand when heated, activate a snap action electrical contact and transfer the electrical signal to the fan controller. In manufacturing, we custom form the wax pellets for different temperature range specifications. All units are calibrated and tested to confirm switch actuation at their specified temperature. The switch is designed using a formed bimetallic contact arm. The bimetal contact movement is achieved using the different expansion rates of two metals fused together. This is a creep action device, provides precise performance. In production, all thermal switches are factory-calibrated to make electrical contact at the specified lower-temperature set point.