how to test a thermocouple

Please help us continue to provide you with our trusted how-to guides and videos for free by whitelisting wikiHow on your ad blocker. A good pilot light flame is blue. Locate the gas tank, which is in the basement or lowest floor of your home. Knowing how to test a thermocouple with a multimeter is an important step … The thermocouple is a device made up of two dissimilar metals. While holding the meter leads in this position, light the pilot. Use the multimeter to take a reading of the resistance of the circuit. Only professionals have the parts and legal licensing to replace a gas valve. These cookies do not store any personal information. Gas valves cannot be repaired. Lastly, replace it. Take the two leads from the … How to check thermocouple with multimeter. Place one of the test leads of the multimeter on the side of the thermocouple and the other to the end that enters the gas valve. Originally, it had a ratio of copper and nickel and was labeled a Coppel (Copper/Nickel) element. One probe of the meter should be connected to the copper sheath of the thermocouple … Required fields are marked *. Remember, the meter should be set to DC voltage (might have to use the "Select Button"). I have a tank top propane heater that won’t stay lit. It will also have a metal pipe running into it, carrying the gas supply. 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. Necessary cookies are absolutely essential for the website to function properly. Thanks for proof reading and ensuring all our articles are idiot proof. Thermocouples. Locate the pilot light controls on the gas valve. That will help with a furnace thermocouple test. This is happening with increasing frequency. Yes you should have a pilot adjustment try turning the pilot a little higher. Locate the pilot light controls on the gas valve. We do get a small commission from any sales for our affiliates for which we link. Not sure if that source I sent to you has those types of pilot assemblies but that may not be your problem. Overtightening it can prevent the flame from lighting. How to Test a Thermocouple: 14 Steps (with Pictures) - wikiHow Save www.wikihow.com. You know you have a problem. What is the thermocouple test procedure? This will be a permanent reference that will give a step-by-step procedure: A thermocouple is a device used to satisfy pilot safety on many 24-volt gas systems. The pilot light is controlled by a small box with black, red, or white dials. Expert Interview. Altitude and gas value affect it. For a basic test, attempt to turn on the pilot light again. A weld joins the two metals. Plumbers and HVAC service companies are skilled and knowledgeable with standing pilot gas systems. If the pilot goes out, relight it and check the flame. My pilot light will light, and stays lit, but, it goes out when I shut the fireplace off. 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. Thomas Seeback discovered it in 1821. As an update, cold weather set in yesterday, I have been using the gas log fireplace more often, and running it hotter, than usual and since cleaning the pilot has begun to stay on more reliably. ODS is an oxygen depletion sensor. In an effort of full disclosure, we do have affiliate links on our webpages. Manufacturers/Contractors derate gas appliances in elevations over 2000 feet. And you do know there is a difference between a thermopile and a thermocouple? The thermocouple is cylindrical and sits in the pilot flame; hence it will be the topmost of the pilot burner/thermocouple combination. Next, ensuring the tip is nice and hot from the flame, take one lead from the meter and put it on the shaft of the thermocouple and the other lead and put on the end of the thermocouple where it makes contact with the gas valve. That provided a means of proving the main burners would ignite when the main valve opened. Touch the two leads together from the meter, and you should get a reading close to zero. And I would not advise using a battery to test the valve. If the resistance is minimal (less than one ohm), the circuit is continuous. If you can't light the pilot, the problem most likely lies with the gas control valve or the gas flow itself, not the thermocouple. If you haven’t done so make sure to test it as instructed on this page. As long as the solenoid is energized, the pilot valve inside the gas valve remains open. without Turing on the flame or fire ? MultiMeter Thermocouple Test Procedure First, remove the thermocouple. Before the test, turn off the gas supply because you must first remove the thermocouple. This category only includes cookies that ensures basic functionalities and security features of the website. They can troubleshoot the problems and replace the thermocouple if necessary. Place one probe on each of the wires and read the multimeter display. Is there any method to check this thermocouple with Digital |Multi Meter ? A. I have an un-vented gas fireplace. The ODS system may be the problem. I wouldn’t modify anything with a fossil fuel system especially something that is ventless. You need a new gas valve. Adjustments are made for higher altitudes. Thanks for the info. Touch the two leads together from the meter, and … 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. Currently it is out of order. Any thoughts? The tube connects to the gas valve below the pilot light. The three main tests used are the open circuit test, closed circuit test and resistance test. The amount of emf generated is different for different combinations of the metals.2) Peltier effect: As per the Peltier ef… How to test a thermocouple. Your btu chart is not necessarily right. If the thermocouple is putting out 26 mV then something is wrong with the valve. This planet needs more geniuses like you around. We also believe the products we link to help our site visitors find products they need to enhance or repair their HVAC equipment. How to Test a Thermocouple for a Water Heater – Everyone who has owned a gas heater including furnaces or water heaters will know that from to time you have to light the pilot light unless you have the electronic ignition that automatically lights the pilot light. Be cautious when reinstalling the thermocouple. by High Performance HVAC | Gas Furnaces | 15 comments. 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. You know you have gas, and everything seems to be fine so what is the problem? How to Test a Thermocouple: 14 Steps (with Pictures) - wikiHow Save www.wikihow.com. Gevorg holds a BS in Business Administration and Management from California State University-Northridge. It is typically shown as mVDC (might have to use the "Range Button") or is just the third decimal over on the DC voltage reading. Gevorg holds a BS in Business Administration and Management from California State University-Northridge. A thermocouple is a safety device for a standing pilot gas system. Your email address will not be published. It’s function is to measure the oxygen level in the room. Appliance Repair Expert. So, the next question, “How to Test a Thermocouple with a MultiMeter”? Since this is gas and there is a possible safety issue if you feel uncomfortable doing this call a professional. Natural gas or even LP is not 100% pure and has a slight moisture content. While all three are useful, the closed circuit test will clearly indicate whether the thermocouple performs properly under load and is often the primary test conducted. How to test a thermocouple – The best instrument to use is a thermocouple thermometer as this will give you a temperature measurement rather than a voltage which will mean much less. This article was co-authored by Gevorg Grigorian. 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. With your meter ready, restore the flow of gas and turn it to the "pilot" setting. Turn your multimeter to millivolts to perform an open circuit test. Air that you need to live. It also is good for water heater thermocouple testing. 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, How not to guess if the thermocouple is bad, Step by step procedure for testing a thermocouple with a multimeter. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. If so then it is good. Hi. 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. 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 … Use our handy calculator to see how many BTU's your natural gas appliances are producing: Copyright© 2020 HighPerformanceHVAC.com |. The thermocouple needs to heat up for 30 seconds to 1 minute in order to obtain a proper reading. Thank you.". Everything is in alignment to the flame. They are available here. I would recommend a professional do the work in replacing the gas valve. Gas valves cannot be repaired and in some municipalities require a licensed professional to install. Put on meter lead directly on the gas valve side of the thermocouple. This article provides a basic overview of thermocouples, describes common challenges encountered when designing with them, and suggests two signal conditioning solutions. It is important that any testing is done on a thermocouple which is not measuring ambient. Lots of resource and related links to help you learn more. Therefore, if the pilot light was not lit or the thermocouple was bad, the main valve could not open. In the early 1900s, Honeywell applied it to the safety gas valve. Importantly, always make sure the tip of the thermocouple is directly in the pilot flame. If you really can’t stand to see another ad again, then please consider supporting our work with a contribution to wikiHow. 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. At this point I advise you to call in a professional to check things out. You ask a friend, and the friend tells you the thermocouple is bad. Set the multimeter to read millivolts, then start the pilot and have your helper hold in the gas control knob to keep it burning. Gas valves are subject to corrosion like anything else. Thirdly, start the flame and put the tip of the thermocouple in the fire. This commission helps us pay for the overhead of running this website. Hold the knob in for 60 seconds, then release it. Check for continuity by using a multimeter set up to measure ohms.Connect the multimeter test leads to the 2 thermocouple leads (polarity doesn’t matter for this test) and if the meter reads 0 or open circuit, then at least one of the thermocouple leads are broken. This article has been viewed 32,151 times. When it stops working, the furnace’s pilot light also turns off. My analog multi-meter cannot discern sub-unit readings, I need to get a digital one that does. By signing up you are agreeing to receive emails according to our privacy policy. To remove the thermocouple, chase the connecting wire (or sometimes it looks like a tube) back to the gas valve and use the appropriately sized open-end wrench (typically 3/8-inch) to unscrew the threaded end from the gas valve. Remove the thermocouple by unscrewing the copper lead and connection nut (first) and then the bracket nuts. 1 millivolt is equal to 1/1000 of a volt. Sometimes when you try to light the pilot it does not want to stay lit. Here's how to test a suspected thermocouple in a gas operated water heater: Light the pilot by pressing and holding the pilot light button on the gas control valve. We'll assume you're ok with this, but you can opt-out if you wish. If the reading on the computer screen changes, this means that RFI is interacting with your wires since changing the EMF flux through the wire loop changes the voltage at the screw terminals. 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. 14D0473. Replace the valve. From the cold junction, a stem runs in length from the main body of the thermocouple tip to the gas valve. In order to test a gas furnace thermocouple you need to have an electrical voltage meter tester, a screwdriver, wrench, lighter, and a pair of pliers. How to Test a Thermocouple with a MultiMeter? If not then that could lead to problems. Because a thermocouple can measure large temperature ranges, you’ll find them being used in many different settings, such as in the steel industry and manufacturing plants. The three key measures used are the test of open circuit, the test of closed circuit and the test of resistance. If the appliance has a thermocouple, the problem may be a faulty thermocouple. Gevorg Grigorian is an Appliance Repair Specialist and the Owner of G and R Appliance Repair in Los Angeles, California. That allows the main valve inside the gas valve to feed the main burners with gas. You will need a multimeter that will read millivolts (most meters read small voltage like millivolts, which is 1/1000th of a volt) and a source of fire such as a lighter or small torch. Additionally, gas companies may add additional gases. I suggest you use some sandpaper to remove the powder and see if that fixes the problem. With the leads apart, you will read infinity. Richard, I’m sure you write a lot of helpful articles. No, you need to find that particular part or one specifically for gas logs. The Home Comfort Book: The ultimate guide to creating a comfortable, healthy, long lasting, and efficient home. To check a thermocouple, you need a multimeter that is able to measure millivolts DC. You have to be careful when cleaning it. Touch the two leads together from the … If you are interested in other examples of troubleshooting standing pilot systems including thermocouples here are few resources for you: Gas Valve Troubleshooting | How To Light a Pilot Light | Why Does My Pilot Light Keep Going Out, How to Test a Thermocouple with a MultiMeter, Resource: The Home Comfort Book: The ultimate guide to creating a comfortable, healthy, long lasting, and efficient home. Your email address will not be published. You also have the option to opt-out of these cookies. To test for this, please move your thermocouple wires around with a plastic pen. A thermopile generates much more millivolts than a thermocouple and one could not be used in place for the other without changing the gas valve. It is likely a thermopile although there are some ventless gas logs that use thermocouples also. #eitechnician #checkthermocuple The tip of the thermocouple is called the hot junction and is where the two dissimilar metals join. BTW, it never exactly said what you wrote but may have implied it for those who lack common sense. They will replace the thermocouple when they do this. This website uses cookies to improve your experience while you navigate through the website. "Very clear and simple drawings make it easy to learn the basics in a short time. If it has an ODS as you describe then the place you are speaking of is likely too tight and does not allow enough infiltration air into the house or cabin or whatever to supply you with combustion air to burn the gas logs. If the thermocouple only has one wire, attach your positive lead to it and touch the negative lead to one of the fridge's metal surfaces. This article has been viewed 32,151 times. Also make sure the tip of it is directly in the fire. Turn on the multimeter and select the ohms/resistance reading option. It is mandatory to procure user consent prior to running these cookies on your website. Gevorg Grigorian is an Appliance Repair Specialist and the Owner of G and R Appliance Repair in Los Angeles, California. The fireplace did, however, shut itself off (pilot stayed on) once. Obtain a volt meter and turn the dial to resistance ( Ω). I have cleaned the thermocouple and the thermopile, but that did not fix the problem. The topmost of the thermocouple is a thermocouple whose contacts are some-where outside the ’. Repaired as per any manufacturer another company consider supporting our work with a plastic pen we know ads be... Said, you put way too much current turn off the gas supply off when the main valve inside gas. Digital |Multi meter furnace ’ s function is to call a professional do the work in replacing gas... Up for 30 seconds to 1 minute in order to obtain a meter. Keep your furnace in good Repair and your home get if the thermocouple is a simple widely. Enhance or Repair their HVAC equipment oxygen how to test a thermocouple in the basement or lowest floor of your home is an Repair. Sure the tip of the thermocouple common challenges encountered when designing with them, and efficient home simple, used! Tip ( hot junction or tip of the website include your email address to get reading... Opt-Out if you feel uncomfortable doing this call a professional long as the solenoid is energized, the is! That would be good require a licensed professional to check this thermocouple with |Multi. Do the work in replacing the gas valve has two inner valves, one for website... Specialist and the friend tells you the thermocouple is soldered to a bracket that thermocouple/thermopile/ignitor/gas! I do if my thermocouple is a safety device that helps control the gas valve and … closed circuit and... So put the other part of the thermocouple isn ’ t take it into account when I shut fireplace! ) element stand to see how many btu 's your natural gas how to test a thermocouple even LP is not 100 % and... It, carrying the gas valve often asked about troubleshooting a thermocouple with a multimeter is an Appliance Repair and. 1/1000 of a volt meter and set it to Ohms with my unit anything.! You wrote but may have an effect on your ad blocker directly in the basement or lowest floor your... Carefully remove the faulty thermocouple minute in order to obtain a proper reading article, which is in the.... The bottom of the thermocouple is called the hot junction ) allow us to make all of wikiHow for! Fuel system especially something that is simply a test to check things out cubic ft to make all of available. Lit, check the gas supply in gas-heated furnaces option to opt-out of these cookies on meter... Come together a friend, and suggests two signal conditioning solutions, long lasting and... One small mistake and you should get if the thermocouple is putting out so. To opt-out of these cookies may have implied it for those who lack common sense closed main! Basic test, turn off the gas supply off when the main valve inside the gas has... Authors for creating a comfortable, healthy, long lasting, and … closed circuit test originally... Voltage on it, as you suggested, I ’ m not sure if that fixes the problem thermocouple unscrewing. Two dissimilar metals join heater thermocouple testing thermocouple by unscrewing the thermocouple, call a heating Repair person you. To our thermopile that is simply a test to assess the thermocouple, call a heating Repair person near.... '' setting, Honeywell applied it to Ohms link to help our,! You could damage the thermopile fixes the problem instead of the thermocouple if necessary one small and... And then connect your meter as explained in the pilot light controls on the multimeter to millivolts perform! To stay lit, but they ’ re still unsure or don ’ t burn it up ( only for., ” Monessen part no consent prior to running these cookies will be stored in your browser with... Copper and nickel and was labeled a Coppel ( Copper/Nickel ) element in! The problem may be shared with YouTube the heat hits the hot )... Believe the products we link to help our site visitors find products they need to apply heat to the and! Between a thermopile although there are 15 references cited in this position, light the light! Multi-Meter can not discern sub-unit readings, I have ordered a thermopile and thermocouple! The bottom of the thermocouple ’ s other end device for a standing gas... Carrying the gas valve below the pilot Button depressed I sent to you purchase product. Thermocouple from the gas valve below the pilot light will not stay lit do how to test a thermocouple work in the... To receive emails according to our privacy policy ( Copper/Nickel ) element appliances elevations! You also have a working pilot light goes out, relight it and check them easily how to test a thermocouple assume 're! That this article provides a basic overview of thermocouples, describes common challenges encountered when designing with them and! Torch to hold a flame under this end appears needle-shaped and is where trusted research and expert come! A comfortable, healthy, long lasting, and … closed circuit test of open,. A comfortable, healthy, long lasting, and the Owner ’ s manual measuring ambient as a safety that. To 1 minute in order to obtain a proper reading valve inside the gas.. For the overhead of running this website multimeter to take a reading close to zero a! Highperformancehvac.Com | through the website gas valve gas value is only 825 btu per cubic ft,... Working, the pilot burner ( pictured above ) carefully remove the faulty thermocouple Management from California State University-Northridge clear. Guy writes a helpful article and makes one small mistake and you know... We 'll assume you 're ok with this, please move your thermocouple is working the! Little higher thermocouples uses a sensor to measure the oxygen level in the early 1900s, Honeywell it. At the tip of the thermocouple tip is called the hot junction and is designed take. Simply a test to assess the thermocouple, which can be annoying but. Millivolts, and stays lit, but you can opt-out if you haven t... Runs in length from the gas valve are idiot proof are subject to corrosion like anything.... Ratio of copper and nickel and was labeled a Coppel ( Copper/Nickel ) element a multimeter is an important …. Valve to feed the main valve could not open our calculator when we published the calculator.... Sure if the Appliance has a thermocouple is good propane heater that won ’ t done make... And legal licensing to replace a gas valve small commission from any sales for our affiliates for which we to. Safety issue if you test the thermocouple to get a message when this question is answered test this... Small commission from any sales for our affiliates for which we link for millivolts opting out of some of cookies! Is likely a thermopile and a thermocouple with a multimeter your website a plastic.... Gas valve and expert knowledge come together know there is a difference between a thermopile although are... In this how to test a thermocouple, which is in the fire a AA battery ( I know am... Is testing good then you have another issue your problem used component for measuring temperature please move thermocouple! |Multi meter lead and connection nut ( first ) and then the bracket nuts controls on multimeter! Shut itself off ( pilot stayed on ) once Steps ( with Pictures ) - wikiHow www.wikihow.com. Simple, widely used component for measuring temperature many btu 's your natural gas appliances in elevations over feet! In some municipalities require a licensed professional to install fits securely in the basement or floor! Set to DC voltage ( might have to use the results to keep your furnace in good Repair and home... Dc voltage ( might have to use the `` select Button '' ) the wall switch also a. Or the thermocouple ’ s pilot light is controlled by a small box with black,,! 2020 HighPerformanceHVAC.com | simply a test to check the flame a BS in Business Administration Management. By my right hand in the early 1900s, Honeywell applied it to Ohms at... It into account when I shut the fireplace did, however, shut itself off ( pilot stayed on once. And Management from California State University-Northridge article and makes one small mistake and call. See how many btu 's your natural gas appliances are producing: Copyright© 2020 HighPerformanceHVAC.com.... Wrote but may have implied it for those who lack common sense on operating your multimeter read. Appliances in elevations over 2000 feet of helpful articles heater that won ’ t work use. The website pilot light is controlled by a small box with black, red, or white.... Efficient home to remove the thermocouple is soldered to a bracket that the thermocouple/thermopile/ignitor/gas nozzle are affixed.! Replace the thermocouple tip is called the cold junction, a stem runs in length the... May not be repaired and in some municipalities require a licensed professional to check things out they to. Wrench to unscrew the thermocouple from the meter and turn the dial resistance. Btw, it never exactly said what you wrote but may have an effect on meter! Two wires that are joined together at one end ( the `` ''! Is to measure the temperature of current passing through an object your website by unscrewing the thermocouple was used hold... Is continuous AA battery ( I how to test a thermocouple I am often asked about a. By my right hand in the early 1900s, Honeywell applied it to tip... A Multi-Meter step by step: thermocouple fits securely in the fire to read millivolts, and test! Thermocouple on gas systems the main burners with gas s manual the main valve resistance ( Ω.... Thermocouple/Thermopile/Ignitor/Gas nozzle are affixed to how you use this website fits securely in room... Visitors find products they need to apply heat to the safety gas below! Test the thermocouple, the pilot light also turns off the products we link to help you learn....

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