Why do thermocouples fail?

Why do thermocouples fail? 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.

How do you know if you have a bad thermocouple? 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 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 long should a thermocouple last? In effect, new thermocouples were installed into contaminated tubes, causing the degradation of the sensors and generating greater than a 100°F shift in accuracy. In this scenario, thermocouple life, which should have been close to one year, was shortened to within a week.

Why do thermocouples fail? – Related Questions

Can a thermocouple fail?

There are any number of ways a thermocouple can fail. It can short out, the sheath can fail, it can be damaged during operation or installation, it can be improperly installed, etc. The key is to perform a thorough root-cause analysis and prevent the failure again in the future, if possible.

How much does it cost to fix a thermocouple?

The thermocouple is an apparatus that senses whether the pilot light is lit and triggers the gas control valve. Repairs typically cost about $150 to have it done professionally, though a new thermocouple itself only costs about $20 on average.

Will a pilot stay lit with a bad thermocouple?

What is a 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.

Can I replace a thermocouple myself?

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. Then unfasten the three nuts that hold the thermocouple and the two gas tubes to the valve. The burner typically sits loosely—or under clips—in the burning chamber and just slides out.

Can you clean a thermocouple?

The best way to clean your thermocouple is to use either a piece of steel wool or the coarse side of a sponge to gently clean off any soot or other remnants. You can use a pencil eraser to clean between the threads of the screw that connects the thermocouple to the control valve of your system.

Should I replace my thermocouple?

If your pilot light won’t stay lit, the thermocouple probably needs to be replaced. A new one costs about $5 to $10 and is easy to install: Turn off the gas supply.

How do you test a thermocouple?

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.

Do thermocouples wear out?

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.

Can you overheat a thermocouple?

Overheating. The welding process can ruin the thermocouple if carried out incorrectly. Overheating the thermocouple with the welding tools can degrade the wire. In addition, the gas and atmosphere near the wire can enter the thermocouple metal, changing its characteristics.

How do you prevent a thermocouple from failing?

This is due to the formation of oxide scales on the surface of the thermoelements. Oxidation can be prevented by using a mineral insulated cable, the outer sheath of a thermocouple will protect the wires inside.

Can a thermocouple work intermittently?

a safety device that has started to go bad, or has failed permanently. In this client’s case, the thermocouple was initially working intermittently, and then finally failed. This allowed the gas to flow long enough to heat up the thermocouple and generate some electrical current flowing back to the gas valve.

How much should a plumber charge to replace a thermocouple?

Thermocouple Replacement Cost

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.

Why does the pilot keep going out?

If the pilot light goes out, the thermocouple senses the drop in temperature and signals for the gas valve to close. If you have a faulty thermocouple is the most common reason that your pilot light is malfunctioning. Over time your water heater will collect dirt, dust and other kinds of debris.

What would cause a pilot light to not stay lit?

If your pilot light won’t stay alight, it might be the thermocouple. Sometimes dust buildup collects on the thermocouple and blocks the sensor. Try cleaning the thermocouple and then relighting the pilot light. If it continues to go out, the thermocouple might need to be replaced.

What’s the difference between a thermopile and a thermocouple?

The main difference between Thermocouple and Thermopile is their method of measurement. The thermocouple is a thermoelectric instrument, while the thermopile is an instrument that modifies thermal energy into electrical output.

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.

How do I clean thermopile thermocouple?

To quickly clean your thermopile, turn off the gas supply. With the help of a stainless steel brush and fine-grit sandpaper, you can scrub off as much piled up soot as possible.

How do you adjust a thermocouple?

Adjusting the Thermocouple

Correcting the first condition is a simple process. Simply shut off the gas, reach under the burner and push or pull the probe to reposition it. If the thermocouple is faulty, remove it by unscrewing it from the burner and pulling it out. Reverse the procedure to install a new one.

Does the gas shut off when pilot light goes out?

The pilot light provides a small flame that ignites the gas needed to operate the appliance. This is because all modern gas appliances with pilot lights have a fail-safe device that closes off the gas to the appliance in the case when the pilot may go out. The fail-safe device is comprised of a thermocouple.

Can a pilot light cause carbon monoxide?

A pilot light should be a crisp blue colour. A yellow or orange pilot light will produce carbon monoxide – an odourless, colourless gas that can fill your home and cause carbon monoxide poisoning. Symptoms of this condition include dizziness, headache, fatigue, nausea, unconsciousness, brain damage and death.

Why does my thermocouple keeps burning out?

It’s Dirty. Soot buildup on the thermocouple may block the flame. Under constant exposure to a hot flame, a thermocouple wears down over time. Even a slight residue can make the thermocouple malfunction.