You don't need tools or training to get your furnace ready for fall. You need about half an hour, a new filter and a flashlight. These seven checks are the same things a technician looks at first, and none of them involve opening anything that holds a flame or gas.
Before you start, find the service switch for the furnace. It usually looks like a light switch mounted on or near the unit. If you can't find it, use the breaker. Any time you remove a panel or reach near the blower, the power should be off.
The 7-step check
- Shut off power and replace the filter. Turn off the furnace switch, pull the old filter and read the size printed on the frame. Install the new one with the airflow arrow pointing toward the blower. A one-inch filter usually needs changing every one to three months. Thicker media filters last longer. Turn the power back on once the filter door is closed.
- Test the thermostat in heat mode. Replace the batteries if it uses them. Switch to heat and set the temperature a few degrees above the room. The furnace should start within a few minutes. If nothing happens, make sure the furnace switch is on and the breaker hasn't tripped before you call.
- Open and clear the vents and returns. Walk the house and make sure supply registers are open and not covered by rugs or furniture. Return grilles need clear space too. A blocked return starves the furnace of air and can make it overheat.
- Clear the space around the furnace. Move storage boxes, laundry and anything else away from the unit. Gas furnaces and water heaters need room for combustion air and room for service. Keep paint, gasoline, solvents and cleaning chemicals away from them entirely, since fumes from those products can be drawn into the burners.
- Look over the flue pipe without touching it. Follow the vent pipe from the furnace to where it leaves the room. Look for gaps at the joints, sagging sections, rust or white crusty residue. On a high-efficiency furnace with plastic vent pipes, go outside and check that the intake and exhaust openings aren't blocked by leaves, nests or debris. Don't push on or adjust the vent. Report what you find.
- Test your carbon monoxide and smoke detectors. Press the test button on each one and replace batteries. Check the manufacture date on CO alarms, since they wear out and need replacing on the schedule printed on the unit. You want CO detection on every level and near the bedrooms.
- Watch and listen to the first heat cycle. You should hear the inducer motor start, then the igniter glow or click, then see the burners light through the sight window, with the blower coming on a short time later. A brief dusty smell is normal. Banging, repeated attempts to light, or the furnace shutting itself down are not. On a high-efficiency furnace, check the condensate drain tubing and any condensate pump for leaks or standing water.
What to leave to a technician
Handling it like a pro also means knowing where to stop. These belong to a trained technician:
- Anything inside the burner compartment, including the burners, igniter and flame sensor.
- The gas valve, gas pressure and gas piping.
- Heat exchanger inspection, plus combustion and carbon monoxide testing at the flue.
- Electrical components such as capacitors, the control board and limit switches.
- Cleaning the blower wheel and checking motor amp draw.
- Any repair to venting or condensate traps.
Never open the burner compartment or touch the gas valve. If you smell gas, leave the house and call your gas utility from outside. If a CO alarm goes off, get everyone out and call 911.
Next step
If any of the seven checks turned up a problem, or if it has been more than a year since a technician looked inside your furnace, call JM Mechanical at (513) 667-8484 or request service online. A fall heating checkup takes care of the parts you shouldn't touch.