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Gas Burners

Solving Pilot Problems
Lighting a Gas Pilot
Adjusting the Pilot Flame
Cleaning the Pilot Orifice
Cleaning the Burners
Adjusting the Burners


Gas burners can fuel warm-air, hot water, or steam heating systems. When the thermostat in the system calls for heat, the burner's automatic gas valve opens, allowing gas to flow into a manifold and then into venturi tubes where it mixes with air. When the air-gas mixture emerges from the burner ports, the pilot ignites it and heat is created. A thermocouple adjacent to the pilot closes the gas valve if the pilot isn't working.

Solving Pilot Problems

Pilots in gas burners may be electric or gas. For problems with electric pilots, call in a professional. Gas pilots can be relit and cleaned by the homeowner.

Lighting a Gas Pilot

  • Before you try to relight a pilot that has gone out, read the instructions usually printed on the front of the boiler or furnace. If there are none, have your utility company light it or follow these steps:
  • Use the manual control knob on the automatic gas valve to turn off the gas to the main burner and pilot.
  • Allow at least 5 minutes for accumulated gas to dissipate before proceeding.
  • Use extreme caution, and take more time if your fuel is bottled gas -- it doesn't dissipate readily.
  • When the gas has dissipated, set the thermostat well below room temperature.
  • Turn the manual control knob to PILOT and light the pilot, holding the knob there for a minute.
  • Release the knob and turn it to ON.
  • If the pilot doesn't stay on, call the gas company. (Remember to reset the thermostat when the pilot's relit).

Adjusting the Pilot Flame

The pilot flame should be blue and should cover the thermocouple. Before adjusting the flame, turn the thermostat down. Reset it when you're finished with the adjustment.

Cleaning The Pilot Orifice

If you have trouble lighting the pilot, the orifice may be plugged. To clean it:

  • Shut off the gas supply by turning the gas inlet valve handle so it's at a right angle to the pipe.
  • Disconnect the thermocouple tub and the pilot gas line from the automatic gas valve.
  • Remove the bracket holding the pilot and the thermocouple.
  • Use stiff wire to clean the orifice (be careful not to chip it).
  • Reattach the bracket, pilot gas line, and thermocouple tube.
  • Turn on the gas and relight the pilot.

Cleaning the Burners

  • Clogged gas burners and ports heat inefficiently. Clean them at the start of the heating season.
  • To reach the ports, shut off the gas inlet valve and remove the bracket holding the pilot and thermocouple.
  • Remove any screws or nuts holding the burners and maneuver them out of the combustion chamber.
  • Scour the burners with a stiff wire brush.
  • Clean the burner ports with stiff wire that's slightly smaller than the diameter of the openings.
  • After cleaning, reassemble the burners in the combustion chamber, replacing any screws or nuts that secured the burners.
  • Mount the bracket holding the pilot and thermocouple.
  • Turn on the gas and relight the pilot.
  • Be sure to adjust the air-gas rate as explained below.

Adjusting the Burners

For maximum efficiency, burners fueled with natural gas should burn with a bright blue flame that has a soft blue green interior and no yellow tips. (Check with your gas company for the correct colors for other types of gas). To correct the air-natural gas ratio, you'll need to adjust the air shutters.

  • Turn up the thermostat so the burners light.
  • Loosen the lock screws.
  • Slowly open each shutter until the flames are bright blue.
  • Close the shutters gradually until yellow tips appear.
  • Slowly reopen the shutters until the yellow tips just disappear.
  • Tighten the screws.
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