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Sept. 4, 2012
No contractor likes to receive a no-heat call in the dead of winter. First of all, it’s a safety hazard for a homeowner to be without heat. In addition, emergencies make it tough to plan business.

No contractor likes to receive a no-heat call in the dead of winter. First of all, it’s a safety hazard for a homeowner to be without heat. In addition, emergencies make it tough to plan business.

One of the easiest ways to level out emergency calls is to encourage your customers to have their gas furnace systems cleaned and checked before the temperatures drop.

Performing a fall clean-and-check not only gives your customers peace of mind that their furnace will operate properly throughout the winter, it also reinforces your company as the heating and air conditioning expert and helps generate referrals for future business. It’s a win-win.

The following is the clean-and-check procedure recommended by the Nordyne technical services team.

1. Ask questions. When you arrive at the home, speak with the homeowners and ask if they have any concerns regarding the equipment. If you listen carefully, homeowners will give you clues about potential problems. If this is your first visit to the home, ask what prior service or maintenance has been performed on the furnace.

2. Check the thermostat. What is the general condition of the thermostat? Does it need to be replaced? Does the thermostat use batteries, and if so, do they need to be replaced? If the thermostat is programmable, check the programing. Many home-owners do not take full advantage of the energy-saving settings on their programmable thermostat. Also check the installer’s setting to make sure the settings are correct for the installation. Check the low-voltage wiring of the thermostat; is the wire in good shape?

3. Clean the exterior of the furnace. Locate the furnace and check its general condition. If the furnace is dusty and the area around it is dirty, pull out the vacuum, clean around the furnace, and wipe down the furnace cabinet.

4. Inspect the flue and the venting. Make sure the furnace is vented properly; compare it with the installation instructions for the furnace. Make any changes necessary per the installation instructions. If there are any signs of damage or deterioration, replace the damaged section or replace the venting system.

For 80% AFUE furnaces, inspect the way the metal flue is routed. If it’s run to a chimney, check and verify that the flue in the chimney is lined with the proper liner per the furnace installation instructions. If the chimney is not lined, install the proper chimney liner for the application. Also, inspect the termination of the flue to make sure that the correct cap is used.

For 90+% AFUE furnaces, inspect the venting material for any damage. Check that the venting system is properly supported and has the proper pitch back to the furnace for the vent condensation. Verify the size of the venting system to the venting chart in the installation instructions. Make sure that the proper sized pipe and proper amount of elbows are used, and that the drainage of the venting system is correct.

5. Inspect the gas line coming to the furnace. Is it correctly sized? Is it installed properly? Is the gas shut-off valve in a readily accessible location? Verify all of the gas piping requirements with the installation instructions and local codes.

6. Check the filter. Find the location of the furnace filter and inspect for cleanliness. Replace if necessary. Many service calls during the winter are due to a dirty filter. If the furnace filter is an electronic type, remove the cells and pre-filters, and wash them. If the filter is excessively dirty, it may be necessary to use a mild detergent to clean it.

7. Inspect the blower assembly. Remove power from the furnace, take off the doors and inspect the blower assembly. Remove any debris from the blower wheel and clean the assembly if necessary. If the furnace is 90+% AFUE, inspect and clean the secondary heat exchanger coil while the blower assembly is removed.

8. Inspect the burner compartment. Oil the inducer assembly if needed. Remove the flue pipe from the inducer assembly and remove any debris or foreign material (e.g., “birds and balls” — we’ve all been on that call when the furnace will not start on the first day of cold weather because there’s a dead bird or a tennis ball stuck in the flue). Check for any rust on the heat exchanger walls. If rust from furnace condensate is visible, check the gaskets on the secondary heat exchanger panel and inducer assembly. They may be damaged and should be replaced.

9. Remove and inspect the burners. Clean any dust or rust that might have accumulated during the off-season with a wire brush. If there is any damage to the burner, replace it. Check the burner orifices for any cobwebs that may have built up, and remove them. Remove the flame sensor and clean it. Flame sensors must be cleaned with steel wool or a wire brush; do not use sandpaper. Cleaning the flame sensor is an important part of any fall clean-and-check service.

10. Inspect the electrical. Inspect all electrical connections in the furnace. If there are any loose connections, repair them.

11. Check the heat exchanger. Visually inspect the heat exchanger with a flashlight or mirror. Note the condition; if it’s rusted or damaged, a more detailed inspection will be needed.

12. Run the system. Turn the thermostat to “heat” and raise the temperature on the thermostat high enough to keep the furnace running while checking its operation. When at the furnace, shut off the gas supply to the furnace and connect your manometer to measure the gas pressure.

13. Check the system’s sequence of operation. Apply power to furnace. Check the startup sequence. Does it follow the manufacturer’s sequence of operation? When the furnace fires off, check the incoming gas pressure to the furnace. Does it meet the manufacturer’s requirements? Turn on all other gas appliances in the home and recheck the gas pressure at the furnace. Is it still within range? Turn off all of the other gas appliances and remove that call from the furnace. When the furnace cycles down, shut off the gas supply to the furnace, remove the manometer from the inlet side of the gas valve and replace the cap. Connect the manometer to the outlet side of the gas valve, turn on the gas supply to the furnace and apply a call for heat from the thermostat.

Check the sequence of operation again. Does the inducer start and run? Are the pressure switches pulling in? If not, connect a manometer to the pressure switches and measure the pressure. Does it meet the settings? If not, recheck the heat exchanger, condensate drain, and flue piping. Look for any restrictions or blockages.

14. Check the gas pressure. When the burners light up, check the gas pressure. Is the pressure within manufacturer’s specifications? Adjust the gas pressure if necessary. Does the flame sensor prove flame? Check the micro amp reading with you multimeter if needed. Most manufacturers list their micro amp range in the installation instructions.

15. Check the temperature rise of the furnace. Most manufacturers list the temperature rise on the furnace model number label. Verify the temperature rise is within specifications and adjust if needed.

16. Test the safeties. Remove a wire from the main limit; the gas valve should shut the burners down. If the burners do not shut down, troubleshoot the limit circuit. Reconnect the wire, and the furnace should restart the ignition sequence. Next, check the pressure switch function: remove the air tube going to the pressure switch, and the furnace gas valve should shut down the gas to the burners.

17. Remove the call for heat at the thermostat. Allow the furnace to complete its shutdown sequence. Remove your testing equipment and replace the furnace door.

Finally, talk to the homeowner and explain everything you’ve checked and cleaned during the process. Make him or her aware of any potential issues with the equipment and your recommendations. This is also an excellent time to schedule the spring clean and check on the outdoor unit. That means more secured business for you, and another properly operating system for the homeowner.

For more service tips, visit the library of technical training videos at

Doug Priestley is technical services supervisor at Nordyne, O’Fallon, MO. He can be reached at 800/422-4328 or [email protected].