It’s August and that means long days, sunshine, and heat. But it also means that the Earth’s journey around the sun has once again passed its halfway point, and colder weather is sure to follow. That’s why now is the time to be thinking about pre-season furnace tune-ups.

Here are the 21 steps we recommend experienced service technicians take to help keep their customers warm and safe this winter. These steps apply to any manufacturer’s gas furnace.

Please note that this information is intended for experienced service personnel who must follow acceptable servicing practices and be familiar with national and local codes.

1. Check wiring for loose connections, voltage at the indoor unit, and amperage of the indoor motor.

2. Check the condition of the belt and shaft bearings (if applicable).

3. Inspect all gas pipe and connections for leaks.

4. Check the cleanliness of the filter(s) and change if necessary.

5. Check the condition and cleanliness of the burners and heat exchanger, and clean if necessary.

6. Check the cleanliness of the blower assembly, and clean the housing, blower wheel, and blower motor if necessary.

7. On induced draft furnaces, inspect the combustion air inducer and clean if necessary.

8. Inspect the furnace condensate drain and trap (if applicable) for leaks and cracks. Clean the drain and trap, and prime the trap with water.

9. Check the static pressure of the duct system and verify correct airflow.

10. Inspect the furnace return air duct connection to ensure the duct is sealed to the furnace. Check for air leaks on the supply and return ducts, and seal where necessary.

11. Check the temperature rise across the heat exchanger and adjust airflow as necessary per nameplate requirements.

12. Check the condition of the furnace cabinet insulation and repair if necessary.

13. Check operation of the ignition system, controls, and safety devices (gas valve, flame sensor, temperature limits). Check the micro-amp signal to ensure it’s in the correct operating range per the equipment manufacturer’s specifications.

14. Check the system’s sequence of operation to ensure the equipment  starts, operates, and shuts off properly.

15. Evaluate the heat exchanger integrity by inspecting the heat exchanger per the AHRI heat exchanger procedure. This procedure can be viewed at www.ahrinet.org.

16. Ensure sufficient combustion air is available to the furnace. Fresh air grilles and louvers (on the unit and in the room where the furnace is installed) must be open and unobstructed to provide combustion air.

17. On non-condensing furnaces, inspect the furnace venting system to make sure it’s in place, structurally sound, and without holes, corrosion, or blockage. Vent pipe must be clear and free of obstructions and must slope upward away from the furnace.

18. On condensing furnaces, inspect the furnace intake (if applicable) and vent pipes to make sure they’re in place, structurally sound, without holes, blockage, or leakage, and the exhaust pipe is sloped toward the furnace. Inspect terminations to ensure they are free of obstructions and are structurally sound.

19. Clock the gas meter to ensure that the unit is operating at the specified firing rate. Check line and manifold gas pressure and make adjustments as necessary.

20. Perform a complete combustion analysis to ensure proper combustion and operation. Consult the equipment manufacturer’s information for proper combustion values.

21. Verify operation of the home’s cabon monoxide detectors. Carry spare batteries to replace the detectors’ batteries if needed.  

Dennis Wood is manager of technical services, and Dwayne Hall is product services coordinator, for Lennox Industries, Dallas, TX. They can be reached at 972/497-5000.