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How to Check a Gas Pilot Light

How to Check a Gas Pilot Light

While electronic ignition furnaces have been around for a while now, you may still have a gas furnace with a standing pilot light that remains lit all the time. The standing pilot light works in conjunction with a thermocouple to control the ignition of the burners and the flow of gas. The thermocouple senses if the pilot flame is hot enough to ignite the fuel to the burner.

If you have an old furnace that uses a pilot light, it needs to be kept clean burning and properly adjusted to ensure that the furnace operates safely and efficiently.

Inspecting a Gas Furnace Pilot Light Flame

Remove the furnace cover panel to expose the burner assembly and pilot. You should be able to clearly see the flame of the pilot light.

The first thing to check is the color of the flame. A natural gas flame should be a bright blue color with a small amount of yellow at the very tip. A propane flame will have more of a bluish-green flame with a tinge of yellow at the tip. The flame should strong enough to cover about 1/2 inch at the end of the thermocouple tip.

If the flame is too strong and not adjusted correctly, it will be blue and may make a hissing sound as the flame crosses the thermocouple. The pilot should be adjusted to reduce the intensity of the flame.

A yellow flame is caused by lack of oxygen and incomplete combustion. If the pilot light is a weak yellow flame it will not get hot enough to heat the thermocouple to the temperature needed to enable the gas valve to open. This is often caused by a dirty pilot tube tip.

A split flame is usually caused by debris inside the pilot tube.

A flickering or wavering flame is usually caused by a draft. Check to see if there are sources of drafts in the room and take steps to reduce the effects on the furnace.

Have questions about your gas furnace or boiler? Call Gibson's Heating and Plumbing.
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