Originally Posted By: jsavino
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Joe, You would have to disconnect the load side of the switch. I have installed mostly the Honeywell fan/ limit control. All came pre-set at 100 degrees blower off, 150 degrees blower on and 180 degrees limit.
The newer furnaces come through with a circuit board fan control center that operates by time. Some mounted in the blower compartment. You still have a limit control, but just a mechanical switch, wired to a relay that could be set up to 90 seconds from when the furnace comes on. Regardless if the burners fire up or not. So in the case of a burner malfunction the blower will still start and run for a while.
Manufactures installed these controls to extend the life of the heat exchanger. Only one problem for the service man (Me) that if the blower doesn’t operate, you replace the circuit board. Instead of the F/L switch.
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