Setting Fan Limit Switch Oil Furnace

The oil fired furnace fan limit switch shown in our photo below is in use on an oil fired warm air furnace where we can see about 3 4 of the silver colored dial where the fan limit switch settings are made red arrow.

Setting fan limit switch oil furnace.

How it works honeywell furnace temperature fan limit switch control. This is used so that cold air is not blown into a house waiting for the gas flames to heat up enough before the blower turns on. Step 1 open the cover of your circuit breaker box. Identify the circuit breaker switch that controls the electricity to your coleman furnace.

Set the markers to the appropriate settings for your furnace. The gas fired forced air furnace fan limit switch in the photo below is pointed to by the red arrow. Below we detail the functions and normal settings for five controls found inside this device. All is wired correctly and replacing the old fan limit switch made no difference.

My oil furnace fan turns on only after the burner shuts down but if adjusted to lower fan on off settings the fan never shuts down. For a general guide set the two lowest ones from the furthest left to 100 and 130 degrees to control when the fan comes on and goes off. Based on where the manual selection switch is set when it reaches the manual setting contacts inside the switch close. There s a problem in your thermostat wiring.

Check with your owner s manual for suggested temperatures. The third marker should be set around 200 degrees as a safety shut off for the burner. Unfortunately you ll need a professional to fix those last 2 problems. It uses a honeywell r8184g relay l4064b fan limit switch and ct87n thermostat.

As we explained above the furnace fan limit control turns the furnace blower on and off at the proper times. But before you call in a pro check to see if your fan limit switch is set correctly. Your furnace fan limit switch is set to manual override the fan limit switch is faulty and needs to be replaced. The furnace s lower limit switch is programmed for automatic reset but the upper limit switch must be manually reset.

A photo of a 1970 s era honeywell l4046t fan limit control installed on a gas furnace showing common wire connections on a gas furnace. When the furnace heat exchanger heats up the bimetal twists causing the round dial shown in the picture to turn.