Trane CNT1662 SPST N/C High Limit L250F

The Trane CNT1662 SPST High Limit L250F is a temperature control device for use with heating and cooling systems including furnaces and air handlers. It shuts down the system when the temperature goes beyond a set top level thus protecting it from overheating. This means that when a switch is described as normally closed (NC), it means that it will be open until it feels that the temperature has risen. In that case, the power supply to the heating element is switched off thus probably saving on equipment since the switch opens (the contact breaks).