How to Light the Standing Pilot Light on a Gas Furnace

Deane Biermeier is an expert contractor with nearly 30 years of experience in all varieties of house restore, maintenance, and remodeling. He is a certified lead carpenter and also holds a certification from the EPA. Deane is a member of The Spruce’s Dwelling Improvement Assessment Board.

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– Working Time: 15 mins
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– Skill Stage: Beginner
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The burner in your gas furnace is ignited either by an digital ignition, present in most modern furnaces, or with a standing pilot flame, which is frequent in older-type furnaces which have an annual gas utilization effectivity (AFUE) score of less than 80 %. A gas furnace’s standing pilot, through which the flame is lit always, is generally referred to as a pilot light.

It doesn’t matter what you call it, its objective is to serve as a small ignition flame for the gas burner. When this little flame fails to operate properly or goes out, it is considered one of the most typical causes that a gas furnace fails to operate. When the thermostat indicators for fuel to be delivered from the gas valve to the burner, the standing pilot ignites the fuel flowing to the burners to heat the air in the combustion chamber.

Because this standing pilot flame (and its good friend, the thermocouple) makes or breaks your furnace’s operation, it is worth spending some time to learn the way it really works. Understanding the furnace pilot is an important part of troubleshooting your gas furnace.

How the Thermocouple and Standing Pilot Work

The thermocouple is an digital machine that senses if the pilot flame is sizzling sufficient to ignite pure gas or propane fuel flowing to the burner. If the thermocouple thinks it’s safe, then it permits the primary gas valve in the pilot assembly to open up and stay open. If the thermocouple or flame sensor doesn’t sense sufficient heat from the pilot flame-resembling when the pilot is extinguished-then the thermocouple shuts off the gas valve delivering gasoline to the burners.

The thermocouple-which is technically called a thermocouple junction-is a machine that comprises two steel wires welded at the ends and positioned inside a protective metal case. The thermocouple sensor is discovered on the enterprise end of the pilot flame and is designed to be positioned in the hottest part of the flame. The other end is linked to the pilot valve body.

As the thermocouple heats up, it produces a small amount of electricity. When heat is known as for and it will get scorching sufficient from the heat of the pilot flame, it sends a sign to open the gas valve by using a solenoid operated by a 24-volt transformer. The thermocouple calls the shots, and by changing heat to an electrical signal, it allows the fuel valve to open.

Once the valve is open, gas is continually supplied to the pilot and to the fuel burners, as known as for by the thermostat. If the pilot goes out, then the thermocouple will get chilly and does not produce an electric signal to open the fuel valve’s solenoid, so the gas valve shuts off the gas provide to the pilot and burners.

What You will Need

Equipment / Instruments

– Flashlight

Supplies

– Lengthy match or wand lighter

Directions

Methods to Relight the Standing Pilot Gentle

A pilot going out is a typical problem with older furnaces, but it is much more frustrating when you do not know learn how to relight it. If possible, discover the instructions adhered inside the furnace door cover or within the furnace’s instruction guide. The method is sort of straightforward, but the steps concerned can differ slightly relying in your furnace mannequin and pilot valve sort.

Two of the most common forms of pilot valve body assemblies have either a purple reset button and a fuel valve or no reset button and a valve knob that may be depressed. But whichever sort you have obtained, if in case you have an older model furnace with a standing pilot (flame is lit all the time), then that is the fundamental procedure.

1. Flip off the Gas

Flip your thermostat to 80 levels or to a setting that can demand heat. Go to the furnace, and discover the pilot valve, a field-formed machine into which the main gasoline line will run. It is situated near the gas burners and can normally have a fuel cock or valve knob that reads “on,” “pilot,” and “off.” Flip the knob or fuel cock to the OFF place and wait about three minutes for any residual gasoline to clear away. Make sure the thermostat is ready to the “heat” mode.

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2. Discover the Pilot Tube

Find the pilot tube and nozzle located near the gasoline burner tube meeting inside the furnace. If possible, try to use an extended fireplace match if you gentle it. Sometimes the pilot is tough to succeed in. If you do not have a fireplace match, then a butane barbecue grill lighter works properly, too. Get your match or lighter prepared. If you don’t have that, fasten a match to the top of a stick as you light the pilot.

3. Set Gasoline Valve to “Pilot”

Flip the gasoline valve from “off” to “pilot.”

4. Light the Standing Pilot

Place the lit match or ignited lighter tip at the pilot while depressing and holding the reset button or miserable the knob, as applicable. Depress the button or knob for about 30 seconds. This maintains gasoline move to the pilot until the thermocouple will get sizzling sufficient to open the main gas valve.

5. Set Gas Valve to “On”

Once the pilot stays lit, slowly release the button or knob and then flip the gas cock or knob from the “pilot” position to the “on” place. This may ignite the burners and keep the flow of gas provided as required for the burners.

If the burners fail to ignite, then it could also be because the thermocouple didn’t get scorching enough to open the fuel valve. Wait a couple of minutes, then repeat the above procedure. This time, hold the purple reset button or depress the knob for about forty five to 60 seconds. Once the primary furnace burners ignite, modify the thermostat to the specified setting.

Troubleshooting Pilot Flame Issues

If you’ve adopted the previous steps for lighting the pilot and it still does not light or won’t stay lit, then you probably have an issue with the thermocouple or an adjustment needs to be made to the pilot. You may additionally discover that the pilot ignites, but that it’s an anemic-trying flame. If a standing pilot refuses to light or won’t stay lit, it is feasible that it is worn out and needs to be changed.

If the pilot lights but the flame is weak and yellow, it won’t get hot sufficient to heat the thermocouple to its set level and permit the gas valve to open. If your furnace runs on propane, the flame should have a bluish inexperienced flame with a tinge of yellow at the tip. In case your furnace runs on pure fuel, the flame ought to be a shiny blue with the tip of the flame having just a tinge of yellow.

The flame ought to be sturdy sufficient to hit the thermocouple tip about 1/2-inch from the tip finish. If the flame is weak or shaky wanting, examine to see that a breeze or draft shouldn’t be blowing on it.

Adjusting the flame: There’s normally a small screw on the pilot valve physique that can regulate the flame. It can be brought on by a soiled pilot tube tip, which will be corrected by cleaning it gently with a wire brush. Flip the screw as wanted to adjust the flame top.
Flickering or wavering flame: A flame that flickers is usually attributable to a draft.
Yellow flame: A yellow flame is brought on by a lack of air and incomplete combustion.
Split flame: That is normally caused by dirt in the pilot tube. It’s possible you’ll have to consult with the manufacturer’s instructions to seek out the screw. Take a needle or small nail and gently clean the tube. Look for sources of draftiness within the room, and ensure the cowl on the combustion chamber is correctly fitted.

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Understanding the Effectivity Score of Furnaces and Boilers. Workplace of Vitality Effectivity and Renewable Vitality, U.S. Division of Vitality.