Which device locks out heating element operation until indoor blower fan operation is confirmed?

The fan interlock relay is a crucial safety device in HVAC systems that ensures the heating element does not operate until the indoor blower fan is confirmed to be running. This is important because the blower fan is responsible for distributing the heated air throughout the space. If the heating element were to operate without the blower fan functioning, it could cause overheating and potentially damage the heating system or create a fire hazard due to the accumulation of hot air.

By locking out the heating element until the blower is operating, the fan interlock relay helps to maintain safe operating conditions, enhances system efficiency, and ensures that the heating is distributed evenly, preventing localized overheating. This safety feature is key in protecting both the equipment and the occupants of a building from the risks associated with improper heating system operation.