Timed blower delays help residential furnaces heat homes more efficiently. When the furnace burner fires up, the factory-set "On" delay prevents the blower from energizing for 25 to 30 seconds so that it doesn't circulate cold air. The "Off" delay keeps the blower going for 60, 90, 120 or 150 seconds after the burner shuts off to circulate the remaining heat in the exchanger. Although the "On" blower delay isn't usually adjustable, you can set the "Off" delay using the dip switches on the furnace control board.
Disconnect the power supply to the furnace while setting the blower delays. Look for an "On/Off" switch on or near the furnace. Shut off the electricity from your home's main electrical service panel if your furnace isn't equipped with a dedicated "On/Off" switch. Locate the corresponding circuit breaker and move it to the "Off" position.
Take the service access panel off of the front of the furnace. Remove any screws or bolts securing the panel to the furnace cabinet. Slide the access panel straight up and pull it toward you if your furnace uses retaining tabs instead of fasteners. Remove just the blower compartment panel if your furnace has two front service panels; this is the top panel in downflow-style furnaces and the bottom panel in upflow-style models.
Locate the furnace control board inside the blower compartment. Find the dip switches used to control the furnace blower delays; the appropriate block of switches should be labeled "Delay," "Fan" or "Blower."
Look for a dip switch setting diagram on the inside of the blower compartment or on the back of the blower compartment access panel; the dip switch settings vary by furnace brand and model. For Nordyne furnaces, for instance, set the first and second dip switches to "On" for a 60-second delay. Move the first dip switch to "On" and the second to "Off" for a 90-second delay. Set a 120-second delay by flipping the first switch to "Off" and the second to "On." Position both switches to "Off" for a 150-second delay.
Replace the removed service panel and restore the electrical supply to the furnace.
Tips & Warnings
- Because blower delay setting instructions vary by brand and model, you should contact the furnace manufacturer to request a dip switch setting diagram if necessary.
- Electricity for Refrigeration, Heating and Air Conditioning; Russell E. Smith
- Nordyne: Oil-Fired Warm Air Furnaces Maintenance Manual
- Associated Equipment: Furnace Control Board
- Olsen: Oil-Fired Warm Air Furnaces Maintenance Manual
- Photo Credit Jupiterimages/Comstock/Getty Images