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How do I know if my thermocouple is bad on my water heater?
A worn out thermocouple is one of the most common gas water heater problems. When thermocouples wear out, the pilot light goes out, the burner won’t light, and you will have no hot water.
How do you troubleshoot a thermocouple?
Importantly, always make sure the tip of the thermocouple is directly in the pilot flame. If the tip is in the flame, you have held the nob on the gas valve down for longer than a minute, the pilot flame is strong and steady, and the pilot still does not stay lit, then you likely have a problem with the gas valve.
How long should a water heater thermocouple last?
Thermocouples can last up to 10 years if properly installed and maintained, while furnaces can last 15-20 years, although either may wear out sooner in multifamily units.
Will a pilot light on a thermocouple go bad?
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 many ohms should a thermocouple read?
A thermocouple should exhibit very low resistance. Attach the negative lead to the red wire, and the positive lead to the yellow. In this case, the reading will be about three ohms. Thus we can conclude that this sensor is a thermocouple.
How many volts does a thermocouple produce?
A single thermocouple (C Type) is used for a standing pilot system and generally produces around 30 millivolts. This voltage is used by the gas valve to keep the pilot valve solenoid internal to the main gas valve open.
What does an open thermocouple read?
A reading of 18 to 30 mVDC should be expected. Your reading may be negative or positive depending on the polarity, but this is not important. Should your reading be low, check your pilot flame before replacing the thermocouple.
What causes a thermocouple to fail?
METAL FATIGUE Like everything, thermocouples can’t stay new forever. 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.
Can you clean a thermocouple?
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.
How do you bypass a thermocouple?
To bypass the thermocouple: Move the tilts switch wire aside. Remove your thermocouple from the heater using an 8mm wrench. Pull the valve housing aside using your 13mm socket wrench. Remove the valve using your pliers. Put your thermocouple back into position.
Why does my pilot light keep going out after replacing thermocouple?
If your water heater pilot won’t stay lit even after replacing the thermocouple, you most likely have a faulty gas control valve. It is a sign that the valve is failing to open and allow gas to flow to the pilot. You could also be dealing with a tripped or faulty thermal switch.
How do you clean a dirty 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.
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 detach the thermocouple from the burner and take it with you to the home center or hardware store to ensure you buy the right replacement.
Can a thermocouple work intermittently?
In electrical circuits, the most unreliable points are electrical connections. So, if in a thermocouple circuit any of the connections suffer from corrosion or lack of intimate metal-to-metal contact, intermittent operation will result.
Are thermocouples universal?
Honeywell, White Rodgers, and other manufacturers make universal replacement thermocouples, usually with a 30-millivolts (mV) rating for standing-pilot furnaces. Electronic flame sensors are much less universal, and you must find the exact part specified for your furnace model.
Why does my gas water heater pilot light keep going out?
Your thermocouple senses when your pilot light is burning. If it senses that your water heater pilot light keeps going out, the thermocouple will shift off the gas supply to the heater. Over time, thermocouples can malfunction, accumulate dust buildup, or the device can get bent away from the pilot light’s flame.
Is a thermocouple supposed to be red?
A thermocouple is a device used to satisfy pilot safety on many 24-volt gas systems. The flame has to envelop the upper 1/2″ to 3/8″ of the thermocouple and the tip should glow a “dull red”.
How do I know if my thermocouple is accurate?
To determine the initial accuracy of a thermocouple, you simply determine the greater of the two tolerances given. Note that standard and special tolerances for thermocouples are determined using the same method. Multiply 300°C by ±0.0075 which gives ±2.25°C.
How do you calibrate a thermocouple?
A basic calibration process involves heating water to 30°C in a thermal bath. Next, each of two multimeter leads is attached to the free end (cold junction) of the thermocouple – at this point, the multimeter should register zero microvolts as both ends are at the same temperature.
Does a thermocouple produce AC or DC voltage?
Figure4 shows also the filtering and amplification of the thermocouple. Being the thermocouple voltage a DC signal, removal of AC noise through filtering is beneficial; furthermore the thermocouples produce voltage of few tens of mV and for this reason amplification is required.
What is the most common thermocouple failure mode?
The most common failure mode for thermocouples is for them to fail open, this is known as thermocouple burnout. Burnout can result from a variety of reasons including the thermocouple experiencing a temperature in excess of that for which it was designed, metal fatigue, and oxidation.
What is the thermocouple thermometer?
thermocouple, also called thermal junction, thermoelectric thermometer, or thermel, a temperature-measuring device consisting of two wires of different metals joined at each end. One junction is placed where the temperature is to be measured, and the other is kept at a constant lower temperature.
What happens if you use the wrong thermocouple?
Problems Related to the Thermocouple Extension Wire If you accidentally reverse the polarity of the thermocouple lead wires, the measured temperature will be incorrect by the difference in temperature of the two ends of the leads.
