Hi. If not then that could lead to problems. For testing a thermocouple you first have to remove it from the furnace, water heater, or gas appliance where it is installed. It’s function is to measure the oxygen level in the room. Replace the valve. I wouldn’t modify anything with a fossil fuel system especially something that is ventless. You know you have gas, and everything seems to be fine so what is the problem? If the thermocouple is testing good then you likely have a bad gas valve. These cookies will be stored in your browser only with your consent. This guy writes a helpful article and makes one small mistake and you call him a idiot. 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. Many multimeters also indicate continuity with an audio alert. The thermocouple is putting out 26mV so I would think that would be good. A standing pilot gas valve has two inner valves, one for the pilot light and one for the main valve. But opting out of some of these cookies may have an effect on your browsing experience. Step 3 Check the multimeter reading to determine if there is resistance. Add the room temperature to temperature in the lookup table. You need a new gas valve. 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. Finally, Good luck! Calculate the thermocouple’s measurement junction temperature at the following millivolt measurements (rounding to the nearest degree Fahrenheit): • 2.55 mV ; T = deg F They are not the same. Air that you need to live. Place one probe on each of the wires and read the multimeter display. Place one test lead on the side of the thermocouple and the other to the end that screws into the gas valve. Anyway, as you suggested, I have ordered a thermopile that is compatible with my unit. If the pilot goes out, the thermocouple can no longer send the millivoltage that is required to allow the gas valve to stay open, thus sealing the valve to prevent a dangerous gas leak. If the pilot valve is closed the main valve would not open. So you have found the pilot light will not stay lit when you try to light the pilot light. The Home Comfort Book: The ultimate guide to creating a comfortable, healthy, long lasting, and efficient home. you need to apply heat to the tip of the thermocouple to get a reading on your meter as explained in the article. Carefully remove the faulty thermocouple from the gas appliance. The thermocouple consists of two wires that are joined together at one end (the "hot" junction). We'll assume you're ok with this, but you can opt-out if you wish. I would recommend a professional do the work in replacing the gas valve. This is possible because each type of thermocouple uses the same composition of wires. Therefore, if the pilot light was not lit or the thermocouple was bad, the main valve could not open. Turn off the electrical power to your dryer. This fractional voltage energizes a small solenoid designed for millivolts. HOW TO TEST YOUR THERMOCOUPLE: Before testing below components are needed. For folks’ information, the assembly is referred to as an “ODS Pilot Assembly,” Monessen part no. The thermocouple asked the meter to compare two readings because that's how thermocouples work. So, I’m not sure if I have a thermocouple or thermopile issue. If so then it is good. PerfectPrime TL0500, K-Type Sensor Probes Alligator Clip Probe for K-Type Probe Thermocouple Sensor & Meter in Temperature Range from upto 500 °C. A piece of copper wire and it is extended, but the temperature is measured from the connection between the thermocouple wire and the copper wire. What is the thermocouple test procedure? Anything under or hovering around the 20 millivolts mark means the thermocouple needs to be replaced. As long as the solenoid is energized, the pilot valve inside the gas valve remains open. without Turing on the flame or fire ? Is there any method to check this thermocouple with Digital |Multi Meter ? For the test, the type of multimeter with red and black clamps is easiest to … We also believe the products we link to help our site visitors find products they need to enhance or repair their HVAC equipment. If the thermocouple is putting out 26 mV then something is wrong with the valve. I’m sure you write a lot of helpful articles. 14D0473. Accuracy of thermocouple on multimeter; If this is your first visit, be sure to check out the FAQ by clicking the link above. This is not very useful. Method 3: Closed Circuit Test. A type K thermocouple is inserted into a process, with a digital multimeter connected to its terminals. In the early 1900s, Honeywell applied it to the safety gas valve. It has a dial on the front so you can select the function and sensitivity you need, and an LED screen that displays the readout. 1. Turn your multimeter to millivolts to perform an open circuit test. This planet needs more geniuses like you around. The valve will stay open if I connect a AA battery(I know I am putting way too much voltage). The millivolt thermocouple range. They are available here. The multimeter will emit a low voltage through the probes that will test whether the bulb has been burned out. Thermocouple Voltage The connection of the thermocouple to an isothermal block is important for the temperature measurement. To make certain the thermocouple is bad you have to test it. Locate the two wires on the bottom of the bulb and touch a probe to each wire, ensuring that the probes do not touch each other or more than one wire. Method 2: Open Circuit Test. For an accurate thermocouple measurement, the return leads of … Ignite a lighter, or other heat source with a flame, at the opposite end of the thermocouple. My analog multi-meter cannot discern sub-unit readings, I need to get a digital one that does. Since this is gas and there is a possible safety issue if you feel uncomfortable doing this call a professional. We also use third-party cookies that help us analyze and understand how you use this website. The thermocouple needs to heat up for 30 seconds to 1 minute in order to obtain a proper reading. Secondly, turn on the meter and set it to Ohms. Don’t you. Lastly, replace it. Perform a closed circuit test using the thermocouple adapter to achieve a true performance ability under load. Eric Jonas has been writing in small-business advertising and local community newsletters since 1998. 99. 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. Check for continuity by using a multimeter set up to measure ohms. This category only includes cookies that ensures basic functionalities and security features of the website. ODS is an oxygen depletion sensor. It is mandatory to procure user consent prior to running these cookies on your website. This is happening with increasing frequency. The thermocouple is a simple, widely used component for measuring temperature. How to Test a Thermocouple with a MultiMeter? This website uses cookies to improve your experience. You have to be careful when cleaning it. Necessary cookies are absolutely essential for the website to function properly. I have a tank top propane heater that won’t stay lit. Also make sure the tip of it is directly in the fire. A. You are a freaking jerk. $9.99 $ 9. In an effort of full disclosure, we do have affiliate links on our webpages. Prior to his writing career, he became a licensed level II gas technician and continues to work in the field, also authoring educational newsletters for others in the business. Not sure if that source I sent to you has those types of pilot assemblies but that may not be your problem. Method 1: Resistance Test. We’ll see if the thermopile fixes the issue. Use a small flame source to test a thermocouple with a multimeter. Unplug the appliance from the wall, or cut the circuit to … Find your voltage in the K-type lookup table 4. Put the other lead on the copper line as shown by my right hand in the picture above. Plug the thermocouple into the meter to read air temperature, or insert the temperature probe to take temperature readings of liquids, gels or to track the surface temperature of a gas dryer. The reading should be between 25 and 30. 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. A thermocouple is a safety device for a standing pilot gas system. Attach one lead of the multimeter to the silvered end of the thermocouple wire (the part that made contact with the gas valve) and the other lead to the bare copper thermocouple wire. To measure voltage across a circuit element, you have to connect the leads of the meter in parallel with the element. 3.9 out of 5 stars 61. 3. But,It didn’t burn it up(only tested for a few seconds). Required fields are marked *. Thirdly, start the flame and put the tip of the thermocouple in the fire. Gas valves are subject to corrosion like anything else. If the thermocouple has proper continuity, a small resistance reading should be visible on the multimeter. It is consuming too much air. To start viewing messages, select the forum that you want to visit from the selection below. Anything under or hovering around the 20 millivolt… A high resistance reading, such as 40 ohms, suggests that the resistance will cause problems and the thermocouple should be discarded. Thus your multimeter would have been designed to … How to Test a Thermocouple with a Multi-Meter step by step: Thermocouple fits securely in the pilot burner (pictured above). When the heat hits the hot junction or tip of the thermocouple, it produces millivolts. Altitude and gas value affect it. Once it is removed you will need a multimeter that needs to have the ability to read millivolts and a source of fire. Not sure I want to do that. There are four readings we are going to take they are OPEN CIRCUIT - this is taken with the thermocouple disconnected and the meter leads attached to the outside of the thermocouple and the other meter lead attached to the tip of thermocouple. 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. Select the ohms or resistance option on your multimeter. The fireplace did, however, shut itself off (pilot stayed on) once. Adjustments are made for higher altitudes. The thermocouple was used to hold the pilot valve open. Your email address will not be published. The three main tests used are the open circuit test, closed circuit test and resistance test. Fewer than 12 millivolts signifies that the thermocouple is defective. The other, much easier way to measure temperature with your multimeter is by using a meter which has temperature measuring capabilities already built in. Make sure all safety protocols are followed. by High Performance HVAC | Gas Furnaces | 15 comments. Using a digital multimeter, turn it to the millivolt (mV) scale on the DC voltage range. This article provides a basic overview of thermocouples, describes common challenges encountered when designing with them, and suggests two signal conditioning solutions. Thomas Seeback discovered it in 1821. What reading you should get if the thermocouple is good. Let the Testing Begin! Any thoughts? 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. You may have to register before you can post: click the register link above to proceed. SSEYL FLUKE 17B+ Digital Multimeter F17B+ 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. Lots of resource and related links to help you learn more. 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. Make sure that the multimeter to be used can read both ohms/resistance and millivolts. At this point I advise you to call in a professional to check things out. Jonas is currently a graduate student with a Bachelor of Arts in English and rhetoric from McMaster University. This is basically the cold junction compensation. To select between Fahrenheit and Celsius, press the range button. Gas valves cannot be repaired and in some municipalities require a licensed professional to install. Turn on the multimeter and select the ohms/resistance reading option. So how do you test the thermocouple to see if it is bad or not? That will help with a furnace thermocouple test. The thermocouple is a vital safety feature for many gas appliances. As you said, you put way too much voltage on it. In-head thermocouple multimeter check One check you can carry out with a thermocouple is if you short the +ve and -ve wires in a terminal connection head, if the instrument and any compensating cables are setup correctly the instrument will give an ambient reading. If an open or resistance test is being performed, the thermocouple is removed. This website uses cookies to improve your experience while you navigate through the website. A weld joins the two metals. Figure 1. We did add the following: *At sea level. These links will lead to you purchase a product from another company. I did know that I just didn’t take it into account when I made the tool. If the reading on the multimeter indicates an "OL" reading, the thermocouple does not have continuity and is therefore not usable. In our area at 5600 ft our gas value is only 825 btu per cubic ft. Additionally, gas companies may add additional gases. First, attach the thermocouple adapter to the gas valve in the thermocouple's spot. Discretion should be used if the reading is between 21 and 25. Attach the other crocodile clip on the screw that extends out of the side of the adapter. You also have the option to opt-out of these cookies. Touch the two leads together from the meter, and … Adapts Type-K thermocouple mini-connector to dual shrouded banana plug inputs Measurement range and accuracy: probe dependent Suitable for low voltage applications (below 30 V AC, 60 V DC) Fluke Digital Multimeter (from fluke.com) Step 2: Depending on the type of test, the thermocouple will be removed or remain installed. A thermocouple does not measure the junction temperature, it measures the difference in temperature between two junctions. No, you need to find that particular part or one specifically for gas logs. Secondly, turn on the meter and set it to Ohms. Lastly, Gas valves cannot be repaired as per any manufacturer. You simply plug in the thermocouple adapter, switch the dial to temperature and start measuring. And you do know there is a difference between a thermopile and a thermocouple? Finally, NOW TURN THE METER TO VOLTS. Put on meter lead directly on the gas valve side of the thermocouple. It is easier to perform this test using crocodile clips attached to the test leads. If the air or oxygen decreases the pilot becomes erratic and lifts off of the thermocouple or thermopile. A thermocouple uses the heat from a flame to produce a millivoltage that controls a gas valve. Turn on the multimeter. Ignite a lighter, or other heat source with a flame, at the opposite end of the thermocouple. Currently it is out of order. The tip of the thermocouple is called the hot junction and is where the two dissimilar metals join. 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. FREE Shipping on orders over $25 shipped by Amazon. Richard, Select the ohms or resistance option on your multimeter. 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. The thermocouple millivolt range should be above 25 millivolts. Originally, it had a ratio of copper and nickel and was labeled a Coppel (Copper/Nickel) element. Your email address will not be published. Carefully remove the faulty thermocouple from the gas appliance. This causes corrosion problems sometimes. Get it as soon as Mon, Jun 22. It is likely a thermopile although there are some ventless gas logs that use thermocouples also. 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 ambient temperature at the DMM’s test lead connections is 84 oF. Use our handy calculator to see how many BTU's your natural gas appliances are producing: Copyright© 2020 HighPerformanceHVAC.com |. Thanks for proof reading and ensuring all our articles are idiot proof. 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. Connect DMM + ve, -ve probe to J1 and J2 of thermocouple (Called cold Junction). BTMETER Auto Multimeter BT-770B,Manual Ranging Digital Avometer NCV Voltmeter Tester,AC DC Amp Ohm Volt Capacitance Voltage Current hFE Hz DMM With Thermocouple for Automotive Circuit Electric Meter $35.61 $ 35 . If your multimeter has been in the room for a while, you can assume this as your junction temperature. This further supports a thermopile issue. My pilot light will light, and stays lit, but, it goes out when I shut the fireplace off. This commission helps us pay for the overhead of running this website. Thermocouples designed for residential gas appliances, such as fireplaces, water heaters and furnaces, are made for 30 Millivolts. I have an un-vented gas fireplace. One junction is placed at the point to be measured, and the other junction is placed at some known reference temperature. Since I cannot locate a thermocouple that looks like the one on this assembly, I would have to modify the bracket so that it might receive an ‘aftermarket’ thermocouple. Good luck! 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. Measure the room temperature. By creating an account you agree to the Hunker, Robert Shaw Controls Company: Thermocouples and Pilot Safeties. The thermocouple is soldered to a bracket that the thermocouple/thermopile/ignitor/gas nozzle are affixed to. The reading should be between 25 and 30. Hunker may earn compensation through affiliate links in this story. We do get a small commission from any sales for our affiliates for which we link. That is simply a test to check the meter for continuity. Natural gas or even LP is not 100% pure and has a slight moisture content. With the leads apart, you will read infinity. Your btu chart is not necessarily right. The reading should be within 12 millivolts and 15 millivolts. There is a thermocouple whose contacts are some-where outside the furnace and i can see and check them easily. 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. Yes you should have a pilot adjustment try turning the pilot a little higher.