How does a gas furnace thermocouple work?

The thermocouple in a gas furnace is designed to keep the gas valve open through its electric voltage. If the pilot light goes out, the loss in heat causes the voltage between the two pieces of metal to drop, and this shuts the valve and reduces the combustion risk.

A thermocouple is a safety device that’s used to detect whether or not your furnace’s pilot light is lit. It contains a metal rod that is placed very close to your pilot light’s flame. If the pilot light goes out, the thermocouple will lose its voltage and the gas line to your furnace will be closed.

Also, how does a thermocouple interrupter work? A thermocouple is an electrical device that responds to temperature change by a change in voltage output. A thermocouple works to produce a small electrical voltage output by connecting two dissimilar metals or two wires forming a measurement junction at the sensor tip of the device.

Also, how do I know if my thermocouple is bad on my furnace?

If the flame lights and goes out when you release the gas control knob after holding it in for the recommended 20 to 30 seconds, that’s the sign of a thermocouple malfunction. Before jumping to the conclusion that the thermocouple is at fault, look at the pilot flame.

How long should a thermocouple last?

The thermocouple unwinds and switches on the fireplace. Thermocouples are rigorously tested and should last for years. Indeed, experts believe a four-year check cycle is all that is needed to make sure things are functioning properly.

Why do thermocouples fail?

The presence of oxygen causes a reaction in the thermocouple that can wear down the part and make the wires become thinner and more brittle. Oxidation can be caused by a small amount of oxygen making its way into a sealed environment and reacting with the pure metal of the thermocouple.

How do you test a thermocouple?

Steps Locate the pilot light controls on the gas valve. Turn the pilot light on for 30 seconds. Release the button to see if the pilot light goes out. Turn off the gas supply to test the thermocouple again. Count to 20 and wait for the pilot light to go out. Listen for clicking near the gas valve.

Are thermocouples universal?

Universal Thermocouples. Universal thermocouples, as the name implies work on most water heaters. They are available online and in home supply stores for a reasonable cost. The length and the thread type are the two concerns when purchasing one.

Can you fix a thermocouple?

A burned out or broken thermocouple should be replaced. To replace a thermocouple: Step 1: Unscrew the copper lead and the connection nut inside the threaded connection to the gas line. Step 2: Under the mounting bracket at the thermocouple tube, unscrew the bracket nut that holds the tube in place.

How do you clean a thermocouple on a furnace?

Use a screwdriver to loosen the screws and remove the thermocouple from the pilot assembly for cleaning. Use a piece of steel wool or the abrasive side of a sponge to gently remove the soot without damaging thermocouple. Avoid using cleaning products, especially those containing flammable chemicals.

How many types of thermocouples are there?

Thermocouple Grade Wire Calibration Type Temperature Range K 32 to 2282°F 0 to 1250°C E 32 to 1652°F 0 to 900°C T 32 to 662°F 0 to 350°C R or S 32 to 2642°F 0 to 1450°C

What does thermocouple look like?

The thermocouple looks like a piece of metal tubing smaller than a soda straw. To find it, first locate the gas control box. This is the box that the main gas line enters, where you turn the gas on in the furnace. The other end of the thermocouple sits in the flame of the pilot light.

How do you adjust a thermocouple?

To adjust the thermocouple, you must tighten the thermocouple nut with a wrench. Take care not to apply too much pressure to the nut — just tighten it slightly. Then try lighting the pilot. If the pilot won’t stay lit, replace the thermocouple with a new one of the same type.

Can you clean a thermocouple?

If the Thermocouple is faulty it will cause the unit to shut down. How to clean? Remove Thermocouple from pilot assembly, using steel wool or emery cloth to lightly clean the tip removing any soot or build up that might have accorded due to an improper pilot flame.

How do you replace a thermocouple on a furnace?

Replacing a Thermocouple Shut off the gas and electrical power to the furnace. Remove the furnace’s access cover. If the furnace has been running, wait 30 minutes for the thermocouple to cool completely. Unscrew the nut that holds the thermocouple end fitting into the gas control valve, using an open-end wrench.

How much should a plumber charge to replace a thermocouple?

Thermocouple Replacement – $20-$150 Calling a professional plumber to install a new thermocouple should only be up to $150. If you do the work yourself, you will only pay the price of the part which is about $20.

Will a pilot light stay lit with a bad thermocouple?

A thermocouple senses the heat of the pilot and allows gas to flow to the burner. A bad thermocouple will shut off gas to both the pilot and the burner so the pilot light won’t stay lit.

How much does a thermocouple cost?

The No. 1 cause of pilot lights that won’t stay lit is a worn-out thermocouple. It’s easy to replace and a new one costs $5 to $10. Rather than trying to unfasten the thermocouple inside the water heater’s burning chamber, it’s easier to remove the whole burner and thermocouple assembly.