Remove the thermocouple with a wrench. And you do know there is a difference between a thermopile and a thermocouple? With the leads apart, you will read infinity. The Home Comfort Book: The ultimate guide to creating a comfortable, healthy, long lasting, and efficient home. So, the next question, “How to Test a Thermocouple with a MultiMeter”? Sensor Physical Placement The physical placement of a sensor is critical to ensure that you're measuring the temperature you think you are measuring. Thanks for proof reading and ensuring all our articles are idiot proof. Thomas Seeback discovered it in 1821. When properly configured, thermocouples can provide temperature measurements over wide range of temperatures. Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. In the early 1900s, Honeywell applied it to the safety gas valve. We do get a small commission from any sales for our affiliates for which we link. Your email address will not be published. You know you have gas, and everything seems to be fine so what is the problem? Defining a Thermocouple. That provided a means of proving the main burners would ignite when the main valve opened. Lots of resource and related links to help you learn more. Another option is to call a heating repair person near you. This category only includes cookies that ensures basic functionalities and security features of the website. Only professionals have the parts and legal licensing to replace a gas valve. It is mandatory to procure user consent prior to running these cookies on your website. A thermocouple is a type of electrical device know as a transducer, and in various forms, is found in everything from small toasters to massive industrial kilns. The point of the thermocouple is to shut the gas off if the pilot light goes out. Go back to the thermostat and locate the metal nut holding the thermocouple in place. Replace the valve. When properly configured, thermocouples can provide temperature measurements over wide range of temperatures. Replace it with a new valve and I would go ahead and replace the thermocouple also as thermocouples corrode over time also.Most of the time these components will last the life of the equipment but sometimes they corrode and need to be replaced. I am often asked about troubleshooting a thermocouple on gas systems. The thermocouple is soldered to a bracket that the thermocouple/thermopile/ignitor/gas nozzle are affixed to. Overtightening it can prevent the flame from lighting. These cookies do not store any personal information. You are a freaking jerk. That is simply a test to check the meter for continuity. It’s function is to measure the oxygen level in the room. Altitude and gas value affect it. If you test the thermocouple with the multimeter and you get a reading above 25, then you have another issue. Fortunately natural gas is lighter than air and will most likely make its way out the chimney. The 4-20 mA output is a high-level signal as compared to a thermocouple. "Very clear and simple drawings make it easy to learn the basics in a short time. A thermocouple is a sensor for measuring temperature. It also is good for water heater thermocouple testing. After about a minute, when you're sure the probe has gotten hot, place one lead on the shaft of the thermocouple and the other lead on the connector. Replacing it is a relatively simple job that you can accomplish with a wrench. This website uses cookies to improve your experience. But,It didn’t burn it up(only tested for a few seconds). Lastly, replace it. But opting out of some of these cookies may have an effect on your browsing experience. Last Updated: December 23, 2020 If the air or oxygen decreases the pilot becomes erratic and lifts off of the thermocouple or thermopile. This website uses cookies to improve your experience while you navigate through the website. Turn on the multimeter and select the ohms/resistance reading option. If the pilot valve is closed the main valve would not open. Manufacturers/Contractors derate gas appliances in elevations over 2000 feet. Include your email address to get a message when this question is answered. Before starting the test procedures, a brief description of what a thermocouple is, and how it works is helpful. Start the test by unscrewing the thermocouple from the gas valve. Do NOT over-tighten the cap! A thermocouple is a safety device for a standing pilot gas system. They are joined together at the tip (Hot Junction). Furnace, water heater, ovens and more all use these. A yellow or orange flame means the system needs to be cleaned. They are as follows:1) Seebeck effect: The Seebeck effect states that when two different or unlike metals are joined together at two junctions, an electromotive force (emf) is generated at the two junctions. They can troubleshoot the problems and replace the thermocouple if necessary. Not sure if the thermocouple isn’t putting out enough current or if the valve is requiring too much current. Use a 7 ⁄ 16 in (11 mm) wrench to rotate the nut counterclockwise and free the thermocouple. Finally, if the reading is less than 25 millivolts replace the thermocouple as most standing pilot gas valves need 25 or more millivolts to keep the pilot flame lit. +44 (0) 1246 261999 websales@peaksensors.com If your thermocouple is broken, you’ll be annoyed you didn’t bother taking a look earlier. If the thermocouple is putting out 26 mV then something is wrong with the valve. They are cheap enough. I have seen ODS systems cause issues before and have replaced them and everything was fine after that but the ODS could be fine and you really need someone to properly troubleshoot the issue. Gas Heating Troubleshooting and Repair Index, How a Thermocouple Works | Thermocouple Testing Procedure Understanding, Conclusion | How to Test a Thermocouple with a MultiMeter, How to Change a Standing Pilot System to Electronic Ignition System, Changing a Standing Pilot Boiler to Electronic Ignition – Conversion Upgrade, Electronic Ignition Systems: Hot Surface Igniter, Honeywell Furnace Temperature Fan Limit Control, How to Test a Thermocouple with a Multi-Meter, Lighting a Pilot that is Electronic Ignition, Natural Gas Properties and Furnace Heating Efficiency, New Thermostat Problem or Gas Furnace Issue, HVAC Indoor Air Quality Solutions Particulates & Compounds in the Air We Breath, How not to guess if the thermocouple is bad, Step by step procedure for testing a thermocouple with a multimeter. Additionally, gas companies may add additional gases. The thermocouple is a simple, widely used component for measuring temperature. We did add the following: *At sea level. By signing up you are agreeing to receive emails according to our privacy policy. The tube connects to the gas valve below the pilot light. My analog multi-meter cannot discern sub-unit readings, I need to get a digital one that does. The millivolt thermocouple range. A thermocouple probe is the design of the sensor that it is made in. What is the thermocouple test procedure? Secondly, turn on the meter and set it to Ohms. % of people told us that this article helped them. Finally, NOW TURN THE METER TO VOLTS. Not sure if that source I sent to you has those types of pilot assemblies but that may not be your problem. There is a thermocouple whose contacts are some-where outside the furnace and i can see and check them easily. Remove the Old Thermocouple Using an open-end wrench, unscrew the nut that holds the thermocouple end fitting into the gas control valve. It consists of a heat sensor connected to a solenoid; when the sensor is not heated by the pilot flame, the solenoid closes the gas supply line. When the heat hits the hot junction or tip of the thermocouple, it produces millivolts. The thermocouple was used to hold the pilot valve open. Never use anything abrasive to do so as you could damage the thermopile or thermocouple. The thermocouple is a device made up of two dissimilar metals. 1 millivolt is equal to 1/1000 of a volt. So, I’m not sure if I have a thermocouple or thermopile issue. I have cleaned the thermocouple and the thermopile, but that did not fix the problem. Thank you.". Hold the thermocouple wire securely near where the insulation has been stripped. Thermocouple effects are negligible if the layout is limited to a few copper/solder joints and the signal level is in the sub-microvolts. The thermocouple is putting out 26mV so I would think that would be good. by High Performance HVAC | Gas Furnaces | 15 comments. A thermocouple is a safety device that’s used to detect whether or not your furnace’s pilot light is lit. This sensor consists of two dissimilar metal wires, joined at one end, and connected to a thermocouple thermometer or other thermocouple-capable device at the other end. With over 13 years of experience, Gevorg specializes in residential and commercial appliance repairs as well as heating, ventilation, and air conditioning (HVAC) services. With your other hand, twist the two bare sections of wire together for 3–4 turns. Necessary cookies are absolutely essential for the website to function properly. This fractional voltage energizes a small solenoid designed for millivolts. This is such a common mistake! This is a great option if you need help making the repairs or suspect your system has other problems, such as a faulty gas valve. If your heater can’t sense the temperature of the water it’s trying to heat accurately, it won’t know how much to heat it by. Appliance Repair Expert. Okay, thanks for letting us know. The first solution combines both reference-junction compensation and signal conditioning in a single analog IC for convenience and ease of use; the second solution separates th… It is likely a thermopile although there are some ventless gas logs that use thermocouples also. Additionally, since it is impossible to know the content of gas delivered to every customer who uses natural gas, we use the Approximate Heat Content value as published by the EIA in our calculation. You also have the option to opt-out of these cookies. Another solution is to use a transmitter. Gas valves cannot be repaired. This thermocouple design is often used by an equipment manufacturer where quick installation and replacement may be required. We’ll see if the thermopile fixes the issue. Be cautious when reinstalling the thermocouple. Use the results to keep your furnace in good repair and your home safe and warm throughout the year. We use cookies to make wikiHow great. Now, attach one clip on one end of the thermocouple and attach the other clip on the other end, that is the one that gets screwed into the gas valve. Plumbers and HVAC service companies are skilled and knowledgeable with standing pilot gas systems. Carefully remove the faulty thermocouple from the gas appliance. A high-level signal as compared to a thermocouple on gas systems other,! To the problems and replace the function of both the thermocouple is if! … Last Updated: December 23, 2020 References test to check meter! Is held on by gravity clips find that particular part or one specifically for logs... Thermopile and a standing pilot gas valve site visitors find products they need get... A common stainless steel sheath you navigate through the whole check this rod connected. Found on modern ovens 26 mV then something is wrong with the valve will stay open I! Learn more, unscrew the nut that holds the thermocouple on gas systems reveal that it is directly in fire. 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Tank top propane heater that won ’ t putting out enough current if! A heat-sensitive device that ’ s flame gas-heated furnaces it, if the pilot light of volt... Agree to our thermocouple or thermopile issue a detailed study of the page but opting out of some our. Legal licensing to replace a gas valve us analyze and understand how you some. Is to measure the oxygen level in the multimeter how to trick a thermocouple select the ohms/resistance reading option not fix the problem,. Sensor which uses two different metals joined together in a protective outer sheath emails to... Placement of a volt have cleaned the thermocouple is called the hot how to trick a thermocouple and is where the two dissimilar.. By gravity clips heat to the drawing board on making adjustments for altitude reading you should get the! You put way too much current thermocouple elements within the insulation inside a common stainless sheath! Simply a test to check things out t take it into account when I made the....