Start with the system you actually have.

Build the equipment record first

Record the indoor and outdoor equipment separately. Capture the manufacturer, model and serial numbers, fuel or energy source, installation date if known, thermostat model, filter location and size, and the contractor that last serviced the system.

The filter is the recurring homeowner task

ENERGY STAR recommends checking the filter monthly, especially during heavy-use seasons, and changing it when dirty; at minimum, its consumer guidance says to change the filter every three months. The exact interval can be shorter depending on the filter, equipment, pets, dust, smoke, construction, and runtime. Follow the filter and equipment instructions where they differ.

Service is more than a filter change

ENERGY STAR recommends annual pre-season checkups. A professional visit may include controls, electrical connections, moving parts, condensate drainage, airflow, coils, refrigerant, and fuel-burning components as applicable. Do not open sealed equipment, handle refrigerant, or attempt combustion work without appropriate qualifications.

• Call for help if the system will not start or stop normally, repeatedly trips a breaker, leaks water, smells like fuel or burning material, makes a new severe noise, or cannot maintain safe temperatures.
• Keep indoor and outdoor equipment clear of stored items, leaves, snow, and other debris without entering or dismantling the unit.