Furnace maintenance checklist

Before winter, replace a loaded filter, clear supply and return grilles, check that the thermostat operates normally, and keep the equipment area accessible. A professional maintenance visit should evaluate electrical connections, moving parts, airflow, temperature rise, combustion, venting, safety controls, condensate, and carbon monoxide as appropriate. Keep records of repairs and model numbers. Maintenance can catch unsafe operation and developing wear, but it cannot guarantee that an older component will not fail during a cold snap.