The thermocouple responds to changes in temperature by producing an electrical current that causes the gas valve that supplies the pilot light to open when the temperature is high or to close when there is no direct heat source.
What controls the gas valve?
The furnace gas valve operates by electromagnets. The primary valve — also known as the safety valve — supplies gas to the pilot light. The second valve — also known as the main valve — allows gas to flow to the burner trays. The thermocouple (or thermopile) generates the power holds the safety valve open.
What does a gas thermocouple do?
The thermocouple is a thermoelectric device that shuts off the gas supply to the water heater if the pilot light goes out. Its function is simple but very important for safety. The thermocouple generates a small amount of electrical current when it has been heated by the flame.
How do you test a thermocouple on a gas valve?
Select the ohms or resistance option on your multimeter. Place one test lead on the side of the thermocouple and the other to the end that screws into the gas valve. If the thermocouple has proper continuity, a small resistance reading should be visible on the multimeter.
What happens when a thermocouple goes out?
If the appliance has a thermocouple, the problem may be a faulty thermocouple. The thermocouple, which operates as a safety device, turns the gas supply off when the pilot light goes out.When a thermocouple fails, the pilot light won’t stay lighted. A burned out or broken thermocouple should be replaced.
How do you know if a gas valve is off?
Gas shutoff valves
When the long side of the nub or handle is parallel to the incoming gas line, it’s open and the gas is flowing. When it’s turned a quarter turn, perpendicular to the incoming pipe, it’s closed.
How much does a gas control valve cost?
Replacing a water heater gas control valve costs $150 to $600.
What causes a thermocouple to fail?
METAL FATIGUE
Changes in temperature can cause regular expansion and contraction in metal, which will cause thermocouples to weaken over time. After enough time, metal fatigue can cause a thermocouple to break.If thermocouples start to give out unusual readings, it may be suffering from metal fatigue.
Should thermocouple be in pilot flame?
If the pilot light goes out, the thermocouple detects it and shuts the valve supplying gas to the pilot. The pilot flame should touch the thermocouple at a specific level.If the flame covers the top of the thermocouple and burns steadily with a yellow tip, that’s just about right.
Can a thermocouple be cleaned?
Yes, you can clean a thermocouple, but the task must be done with a light touch. Remove the thermocouple from the process assembly, using a steel wool or emery cloth, lightly clean the tip removing any build up.
Can you bypass thermocouple?
Realistically, you have just disabled the thermocouple, but you can also reach in and unclip it from its holding bracket where it meets the pilot light. In most cases it will be held on with a gravity clip, but some are held on with a screw that must be removed with a small screwdriver.
How do you trick a thermocouple?
The thermocouple always thinks the pilot is not lit, even if it is. To get hot water, I have to light the pilot, then hold the match on the thermocouple to trick it into thinking the pilot light is touching it. Once it’s warm enough, I pull the match out and turn the knob from “Pilot” to “On”.
How do I know if my thermocouple is bad on my furnace?
If you can’t get the flame to light at all, and you’re sure the gas is on, there’s probably an obstruction in the pilot tube. 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.
Can a thermocouple leak gas?
In a few cases, a malfunctioning thermocouple may allow gas to leak into your home, which is a major problem. That’s why, when you detect problems with your thermocouple, you should turn off the gas immediately before calling in an expert to help.
How often should thermocouple be replaced?
four-year
The fireplace has thermocouples and switches. The thermocouples should last for a long time. According to experts, a four-year check cycle is all that is needed.
Do Thermopiles go bad?
Like the other component parts in your furnace, the thermocouple can wear down over time, producing lower voltage than it should when heated. And the worst part is that you can have a bad thermocouple without even knowing. Therefore, inspecting and testing your thermocouple should be part of your furnace maintenance.
Where should a gas shut off valve be located?
The gas meter and gas service shutoff valve is usually located on the side or in front of the building. If the building has a breezeway, it could be located there.
Which way should gas valve is off?
The long side of your handle is parallel to the incoming gas line, which means your gas in on and flowing. By turning the handle perpendicular to the incoming pipe, you are closing the valve and shutting off the gas.
How long does a gas control valve last?
Gas Valves are routinely checked for 100,000 cycles and are used in equipment that have approximately 15 years life expectancy.
Can you fix a gas valve?
In some instances you can repair a gas valve on a furnace depending on what is causing it to not work properly. However, repairing your gas valve is not usually the most cost effective option since it can be just as expensive to have your gas valve repaired as it would be to have your entire gas valve replaced.
Who can replace a gas valve?
A gas shut-off valve should be installed by a licensed plumber or heating/cooling contractor. Code and regulations need to be followed carefully. For example, all shut-off valves for gas appliances, such as gas stove/oven, gas dryers, and gas fireplaces must be installed within six feet of the appliance.
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