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What is a fan limit control?

Question: What is a fan limit control?

Answer: Fan limit controls are very important for your safety and for proper furnace operation. Fan limit controls that we sell are suitable for all types of forced air heating systems. The fan limit control provides high limit control of the burners and control of the fan motor according to the furnace plenum temperature. When your furnace burners come on the fan limit control measures the temperature inside the furnace’s plenum. When the temperature of your furnace gets warm enough and to the preset temperature on the fan limit control, the control clicks on and causes the furnaces blower fan to kick on and circulate air throughout your home. When your thermostat is satisfied the burners kick off and the fan continues to run until your furnace’s plenum cools down to the fan OFF set point on your fan limit control. The fan limit control turns the fan off. The fan limit control is an important safety device. Let’s say that your furnace’s burners come on but the blower motor is bad and will not start. Without the fan limit control your furnace could over heat and cause a fire! The fan limit control shuts the gas burners down so the furnace will not over heat and cause a fire. The Honeywell fan limit controls that we sell below have a manual fan switch that can be used to override the fan set point and keep the fan running continuously.