HVAC maintenance checklist: what you do and what the pro does

The split: your jobs and the pro's

Most of what keeps a furnace and central air running well is small and regular, and it's yours: the filter, a clear path for air, a working thermostat and a look at the drain. The rest needs tools and training: gas pressure, burners, refrigerant, electrical connections. ENERGY STAR recommends a yearly tune-up, with a contractor checking the cooling system in spring and the heating system in fall, before the busy seasons. It suggests tying those visits to the spring and fall clock changes so you remember.

Your owner's manual comes first. If it gives a different interval for anything below, use the manual.

What you do

• Filter, every monthENERGY STAR says to check the filter monthly, especially in winter and summer, and to change it at least every 3 months. A clogged filter wastes energy and can shorten the equipment's life. Our furnace filter guide covers sizes, MERV and the swap itself.
• Outdoor unit, clear around itTrane's rule of thumb is to keep plants from growing within a 2-foot radius of the air conditioner. Pull leaves, grass clippings and cottonwood fluff off the top and sides. Never run the AC with a cover on it.
• Registers and returns, openFurniture, rugs and drapes over vents choke airflow. Trane lists keeping supply registers and return vents unblocked as a basic owner task. Closing lots of registers to "save" heat isn't a fix either; ask your contractor before you do it.
• Condensate drain, a quick lookFurnaces and air conditioners make water, and a drain line or pump carries it away. ENERGY STAR notes a clogged drain can cause water damage and affect indoor humidity. If you see water around the furnace, a full drain pan or a pump that won't stop running, call for service.
• Thermostat, set for the seasonSwitch it from cool to heat in the fall and back in spring. Replace its batteries if it has them. A programmable or smart thermostat can lower the setting while you're away or asleep.
• Carbon monoxide alarms, testedA gas furnace burns fuel, so CO alarms matter. CPSC recommends them on every level of the home and outside sleeping areas, interconnected if possible, and says to check the batteries regularly. Press the test button when you set the thermostat to heat.

What a tune-up covers

ENERGY STAR lists what a contractor's tune-up should include. For every system:

• Controls and thermostatCheck the settings and the startup cycle, so the system starts, runs and shuts off safely.
• ElectricalTighten connections and measure motor voltage and current.
• Moving partsLubricate them to cut friction and wasted electricity.
• Condensate drainInspect it on the central air conditioner, furnace or heat pump.

For cooling, the tech cleans the indoor and outdoor coils, checks the refrigerant and adjusts it if needed, and cleans and adjusts the blower. ENERGY STAR notes airflow problems can cut efficiency by up to 15 percent. For heating, the tech checks gas or oil connections, gas pressure, burner combustion and the heat exchanger, since problems there can be a fire hazard and a health hazard. Those are not homeowner jobs.

Ask the tech to show you where your filter goes and how your drain is set up. ENERGY STAR suggests the same.

The checklist by season

Spring

Book the cooling tune-up before the first hot spell. Clear winter debris from around the outdoor unit and take off any cover. Check the filter, switch the thermostat to cool and test-run the AC on a mild day, so a problem shows up before you need it.

Summer

Check the filter monthly, since the AC uses the same blower and filter as the furnace. Keep the outdoor unit free of clippings and plants. Glance at the condensate drain now and then.

Fall

Book the heating tune-up. In the Chicago area the furnace usually starts working hard around November, so September and October are the time to get on a contractor's schedule. Test CO and smoke alarms, switch the thermostat to heat and run the furnace once before the first cold night. A burning smell that doesn't go away is a reason to shut it off and call.

Winter

Check the filter monthly. Keep snow and ice away from any furnace vent pipes that exit through a side wall, and keep the area around the furnace clear of storage.

When to call before the tune-up

Don't wait for the scheduled visit if a CO alarm sounds, you smell gas, the furnace short-cycles or won't light, the AC blows warm air, ice forms on the refrigerant lines, or water pools around the equipment. For a CO alarm or a gas smell, get everyone outside first and call from there.

Questions people ask