Installation steps for installing a replacement thermocouple are simple, and are made easier by looking carefully at how and where the old thermocouple was installed and where and how its tubing was routed between the gas valve and the flame sensor position. Type K (chromel-alumel) are the most-widely-used general purpose thermocouple, Vacuum & controlled atmospheres, high temperature kilns, ovens, furnaces, gas turbine engine exhaust monitor, metal industries: aluminum & smelting, Heat treatment, process control, semi-conductor, glass industries, metal industries: ferrous & non-ferrous, Food monitoring, environmental sensors, used in strong magnetic fields, The thermocouple sensor is not properly located and secured in position in the gas flame. Light the pilot by pressing and holding the pilot light button on the gas control valve. Separately a Gaffers & Sattler appliance company still does business in Murray UT. A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. Weird & Wacky, Copyright © 2021 HowStuffWorks, a division of InfoSpace Holdings, LLC, a System1 Company. If the pilot light won't stay on, connect a new thermocouple or thermopile to the gas valve and have a helper heat it with a butane lighter. Learn more about thermocouple response times. If the pilot valve is closed the main valve would not open. Tagged: how does a thermocouple work on a gas valve . A thermocouple works to produce a small electrical voltage output by connecting two dissimilar metals or two wires forming a measurement junction at the sensor tip of the device. If the burner switches off after 2/3 seconds, the thermocouple isn’t working. This article explains what a thermocouple (or thermopile) is, how these devices work, where they are installed, and what goes wrong with thermocouples. The amount of emf generated is different for different combinations of the metals.2) Peltier effect: As per the Peltier ef… In addition to finding electrical wires leading to an igniter at the gas burner or gas pilot, you will also see a tag such as that shown on this gas valve on an A.O. If it's working properly, it should generate more than 25 millivolts when the pilot is on. Therefore, a tester must be added. Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly. Some gas fired heating equipment relies on an electronic ignition to ignite the flame. That is from sending gas to your tank when it is not necessary. will about any thermocouple work on all ventless fire places mine is majestic v32. How does this happen? The thermocouple generates about 20-30 millivolts, enough electricity to keep the part of the gas valve that controls gas flow to the pilot assembly open. Thermocouples are a widely used type of temperature sensor. Furnace gas valves are only seen on gas-fueled forced air furnaces or gas-powered boilers. The thermocouple in a gas furnace is designed to keep the gas valve open through its electric voltage. Sometimes if the gas valve is just barely bad a hotter thermocouple will work for a short time but finding a hotter thermocouple is just hit and miss. The thermocouple senses the gas pilot flame and prevents flow to the main burners when there is inadequate heat to ignite the burner. Thank you. Common causes for the refusal of a gas burner to light when the pilot is on include a bad gas valve or most likely a defective thermocouple or thermocouple connection. Hope someone has some wisdom for me. Thermocouple's indicating end not fully secured into the gas valve. Note: appearance of your Comment below may be delayed: if your comment contains an image, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Typical thermocouple installations include instructions for bending the tubing to avoid sharp bends or nicks. Measuring the millivoltage cannot be done when the thermocouple is connected directly into the solenoid. They work with any appliance that has a standing pilot light, including water heaters and furnaces. Simply put; no flame, no gas flow. If the pilot light goes out, the loss in heat causes the voltage between the two pieces of metal to drop, and this shuts the valve and reduces the combustion risk. If the flame goes out, the thermocouple voltage disappears and closes the gas valve. The valve receives the DC voltage that the thermocouple generates by being heated and magnetizes the power cell located inside the body of the gas valve. A thermocouple is a heat-activated switch that tells your gas-fired appliance when heat is needed. It does this by generating a small electric current -- on the order of 10 to 30 millivolts -- as a signal to the gas valve. A less likely problem is a failed gas control valve. The other end of the thermocouple is attached to the gas valve body. The thermoelectric effect that makes a thermocouple work is called the Seebeck effect, named after the German physicist who discovered it in 1821. Flip on the pilot light using the knob on the tank’s gas valve. When 1 of those 2 metals is heated then the voltage is generated. A brief understanding of how the thermocouple and thermopile work and what can go wrong will help troubleshoot a valve that is malfunctioning. The current actuates a spring mechanism on the gas valve that keeps the valve open. What type of thermocouple use for mini flare? Doing so will almost certainly make it inoperative and thus unsafe. It is thermocouple-operated and does not require electricity to operate. I had to leave the door open to the heater because the connector sticks out too far and when moved the pilot goes out. So, the voltage to open the valves comes from thermocouples and the heat comes from a pilot light. It senses when the pilot light is burning hot enough to light the gas from the main gas valve. How to Inspect Your Furnace’s Thermocouple Sometimes this takes 30 minutes, sometime several hours. A thermocouple tester gives you a contact for the inner wire of the thermocouple. The thermocouple acts as a sensor. (Gaffers and Sattler was an appliance brand (kitchen ranges, heating equipment, air conditioning) owned by Maytag and actually preceded "Maytag" as a company name.The Gaffers Sattler and Maytag Washing Machine Company was founded in 1893 by businessman Frederick Maytag. The thermopile powers a second circuit that operates the main valve. It’s designed to determine whether the pilot light is lit and then subsequently signals the gas valve to open. If it senses the heat is hot enough, it will turn that heat into an electric signal and sends it over to the gas valve and tells it to open and let the gas out. Thermocouples are known for their versatility as temperature sensors therefore commonly used on a wide range of applications - from an industrial usage thermocouple to a regular thermocouple found on utilities and regular appliances. Testing: Grab a Thermocouple Tester on Amazon! Magic Chef found its way back to Maytag in 1986. If the gas valve works fine when the spare thermocouple is being heated by the lighter, you need to replace the old thermocouple or thermopile. How it works: Thermoelectric gas valve is controlled by the thermocouples DC voltage (figure 2). Then the heater works cycling on and off as you would expect. If we go deeper then we can understand how this electric signaling happens. The connecting copper tubing length for a thermocouple is not usually critical, but the tubing must be long enough to reach without stress from the connection at the gas valve to the thermocouple's sensor mount in the gas flame or pilot flame. Patio Heater Thermocouple – Thermocouples function as a safety device for your gas water heater that prevents the gas valve. How often do pressure relief valves need to be replaced? You can think that you have fully screwed in the connector that pushes the end of the thermocouple into the bottom of the gas valve but it may not actually be fully seated. Do not turn on nor try to use gas fired equipment if there is a gas leak. If you’re still unsure or don’t have a working pilot light, test the thermocouple with a multimeter. A gas valve replacement is a common furnace repair in older furnaces or when a gas leak is present. Some of the photos used here are adapted from detailed thermocouple installation instructions provided by American Water Heater provides at http://www.americanwaterheater.com/support/manuals/nat_tc_instr.pdf [1]. The heat from the pilot flame is sensed by the thermocouple and the induced electrical charge actuates an electromagnet inside the gas valve that allows flow to the main burners. I know this one, it has a gizmo called a thermocouple, this is comprised of two dissimilar metals that when heated generate a voltage. If the pilot light goes out, the electrical current stops and the gas valve closes. If your gas fired equipment also uses an igniter wire in addition to the thermocouple, they are often routed together and will need to be removed for thermocouple replacement. Inside your gas-operated water heater is a tiny gas flame called a pilot light, whose purpose is to ignite the burner whenever the temperature falls below the thermostat setting.. Any advice. Watch out: don't modify a thermocouple (other than gentle bending as described in the installation instructions). A standing pilot gas valve has two inner valves, one for the pilot light and one for the main valve. The thermocouple responds to changes in temperature by producing an electrical current that causes the gas valve that supplies the pilot light to open when the temperature is high or to close when there is no direct heat source. Lately it has started acting up. • Intermittent pilot (also known as “spark to pilot”) – Pilot is ignited by a spark generated by an ignition module and electrode. Northridge, CA 91324 USA Tel: (818) 886-3755 also DBA. Vacuum, inert, reducing atmospheres, hot processes, eg: plastic & resin mfg. Something is loose inside, I think. But thermopiles sense temperature without having to contact the object being monitored. If you can't clean it and get it to work a new valve can save the cost of a new furnace. We describe how to find the thermocouple if one is used on your heater, and how the thermocouple is replaced. The thermocouple connecting tubing has been mechanically damaged, crimped, cut or nicked. GAS LP & NATURAL GAS SAFETY HAZARDS Watch out: Some gas fired heating equipment relies on an electronic ignition to ignite the flame. The thermocouples used in building mechanical systems are generally type K: thermocouples used in heating boilers, calorifiers, geyers, gas burner applications (flame sensors). Don't confuse a thermocouple (discussed here) with a different type of temperature sensor, solid-state THERMISTORS used in thermostats. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature. We have run into this problem and also read other accounts of it concerning the Gaffers and Sattler Those devices generally will not use a thermocouple. If your appliance has a flexible electrical wire that connects to a sparking device at the burner or burner pilot, the appliance has no continuously-on pilot - you do not have to light the pilot manually. Building mechanical systems, oil & gas heating, water heaters, gas burner flame safety, water, mild chemicals, gases, dry areas, engines, hospitals & food industry. A dated but still very relevant book about the theory of how thermocouples work. This small charge causes an electromagnet inside the gas valve to open and allow gas to flow to the main burners. I have isolated the valve that interrupts the gas flow if the pilot flame goes out and it has a plunger that requires at least 1 lb of force to move. The power coil needs the DC voltage to stay compressed to allow the gas to flow through the valve. Thomas Seeback discovered it in 1821. This rod is connected to your furnace’s gas valve. Some systems, known as millivolt control systems, extend the thermocouple concept to both open and close the main gas valve as well. After all, the thermocouple is in a flame. Watch out: Before trying a new thermocouple I'd suggest checking for debris in the pilot light orifice or tubing. (This happens because one part of the thermocouple is hotter than the other - this is called the thermoelectric effect.) The thermocouple, which operates as a safety device, turns the gas supply off when the pilot light goes out. Continue pressing the pilot button for 30 to 60 seconds after lighting the pilot light. I seem to remember reading something about them being for safety or something. A thermocouple is basically a safety device on the heater. Follow the instructions in the manual or guide for your heating appliance and also review the installation instructions and bending instructions that came with a replacement thermocouple. Or see THERMOCOUPLE TROUBLESHOOTING FAQs - questions & answers posted originally at this article. with the thermocouple, the gas valve allows gas to flow to main burner until the call for heat is satisfied. As long as the thermocouple is putting out enough voltage, created by contact with the pilot, it allows the gas valve to … The other end of the thermocouple's tubing connects to a port on the gas regulator or gas valve But not all of these systems use a thermocouple. Typically the thermocouple sensor is mounted right in the flame of the pilot light on gas fired heating equipment. Calibration types for thermocouples are specified by the American Society for Testing and Materials(ASTM) according to their temperature versus EMF characteristics in accordance with ITS-90,in standard or special tolerances. That is a less common problem in my experience.Lastly, it's possible that the defect is in a gas flow or clog problem in the pilot light itself. InspectAPedia tolerates no conflicts of interest. When its probes are heated to a certain temperature. A thermocouple is a device used to satisfy pilot safety on many 24-volt gas systems. There are three main types- direct ignition, intermittent pilot, and continuous pilot. Northridge, CA 91324 USA Tel: (818) 886-3755 also DBA, [1] American Water Heater, "Thermocouple Replacement Instructions - Natural Gas Models (All Models Except 30T)", American Water Heater, Johnson TN, Website: http://www.americanwaterheater.com, Tel: 1-800 999-9515, (no address given online) retrieved 10/23/2013, original source: The valve receives the DC voltage that the thermocouple generates by being heated and magnetizes the power cell located inside the body of the gas valve. This signals the valve to stay open. A interrupted thermocouple is a thermocouple that is interupted between the pilot light and the power pack at the back of the gas valve Usually interupted by a high limit thermostat which when activated ie boiler over heats,electrical currect through thermocouple cut,stopping magnetic field in power pack in gas valve,thus closing gas valve and any gas that passes through it,pilot and main burner I don't have any trouble lighting the pilot. When the pilot flame is burning, it heats the probe and causes a current to flow through the thermocouple's circuit. You can test a thermocouple with a voltmeter. Gas ranges and ovens manufactured today are actually very safe. It detects the heat of the flame and generates the voltage that keeps the gas flowing. If the appliance has a thermocouple, the problem may be a faulty thermocouple. Check for these other causes of loss of the gas pilot flame. I have added a picture [above] for you. A bad thermocouple itself can prevent a gas furnace or boiler from working - if you can light the flame at the pilot manually but then the flame goes out when you release the manual gas • Intermittent pilot (also known as “spark to pilot”) – Pilot is ignited by a spark generated by an ignition module and electrode. On 2020-03-28 - by (mod) - gas valve won't open: black wires at the thermocouple? It’s a remarkable feat for so simple and small a device. For a basic test, attempt to turn on the pilot light again. Right next to the pilot light is a small metallic tube known as a thermocouple. Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia. Here, courtesy of Pyrosales, an Australian provider of thermocouple devices, is a complete list of the types of thermocouples and their applications. When the electrical signal is sent from one end of the thermocouple to the other, it activates a solenoid at the base of the gas valve that functions using a 24-volt transformer. In general we think that thermocouples are less accurate and less sensitive temperature sensors than thermistors, but these low-cost and reliable temperature sensing devices have been used successfully in heating equipment such as gas fired furnaces, boilers, and water heaters for decades. I know this one, it has a gizmo called a thermocouple, this is comprised of two dissimilar metals that when heated generate a voltage. "Thermocouple Technical Chart: Temperature Ranges", Thermometrics Corporation, 18714 Parthenia St five years How long does a thermocouple last? I have had to replace my thermocoupler 3 times in 4 years the last one only lasted 3 months can you recommend a brand name and why is this continuing to happen My gas boiler is 35 years old and in good condition The boiler is a Hydrotherm. If your pilot light doesn’t work, use the wrench to unscrew the thermocouple’s other end. Replacement thermocouples using "universal mounting" include clips and fittings that will work on most gas fired heaters and water heaters. There we note that millivolt thermopiles are used in lieu of a simpler thermocouple when the device needs to operate a thermostat as well as the gas valve. January 20, 2019 The stove doesn’t stay lit – Thermocouple problem. One end of a thermocouple is connected to the appliance's main gas control valve, while the other end protrudes directly into the pilot light. In our photo at far left the yellow and blue wires is the safety sensors & direct ignition wiring connected to an igniter that will be found at the pilot light. The power coil needs the DC voltage to stay compressed to allow the gas to flow through the valve. The thermocouple responds to changes in temperature by producing an electrical current that causes the gas valve that supplies the pilot light to open when the temperature is high or to close when there is no direct heat source. Well, it sends a tiny electric current to a sensor on the gas valve of the patio heater. When enough heat is generated in the thermocouple, the gas valve allows gas … Smith gas fired Direct Igntiion water heater (photo at close left). Articles. We often find this problem in southern climates where heating equipment may be installed outdoors or in a shelter exposed to wind. That prevents the main solenoid inside the gas valve from opening. Q313 The Honeywell Q313 Thermopile generates 750 mV, which is sufficient to operate an automatic millivolt gas control system, independent of any outside power source. Now, using the cigarette lighter, heat the end of the thermocouple that is kept in contact with the pilot flame (opposite to the one that gets screwed into the gas valve). insulate it? The working principle of thermocouple is based on three effects, discovered by Seebeck, Peltier and Thomson. You can make your job easier by shutting off the gas supply and removing the old thermocouple intact to help select a replacement model. Now I cannot get the pilot to even try to light. Thermocouples are also used on gas logs and in gas fireplaces or similar devices. I have used canned air to clean and pushed and pulled everything. They are joined together at the tip (Hot Junction). I am GUESSING that they lead to a couple of spill switches that might be located on the draft hood of your heater or right near the burner opening.Those devices sense dangerous spillage of flue gases, are usually heat-activated, and some models require that the switch be manually-reset by pressing a reset button on the switch after it has cooled.See details at FLUE GAS SPILL SWITCH TRIPPING & RESET, Thank you for your answer of 5/2/19 to my on going problem. In essence, it contains everything needed for the operation of a gas fired furnace. In the early 1900s, Honeywell applied it to the safety gas valve. This voltage in turn can be used to cause a gas valve to open or remain open, or to close, stopping the supply of LP or natural gas fuel should a pilot light or gas flame go out on a heating appliance. Not all gas water heaters have a thermocouple. How "smart" cookware uses embedded thermocouples to prevent pans burning your … the sensor connector not fully screwed-in. Thermocouples can be connected in series as thermocouple pairs with a junction located on either side of a thermal resistance layer. Click to see full answer. Apart from testing the open circuit voltage of the thermocouple, and the near short-circuit DC continuity through the thermocouple gas valve coil, the easiest non-specialist test is substitution of a known good gas valve. The fireplace uses this voltage to open the gas valve, allowing gas to flow out and start a fire. Sudden drafts. Try replacing it and be sure the new one is properly placed. That's because unlike in the past where most gas ranges and wall ovens used a freestanding pilot light, today's gas ovens rely on an oven safety valve that will not permit gas to flow to the burner unless the igniter is glowing red producing enough heat to ignite the gas when it reaches the igniter. A combination gas valve contains a handle, a thermocouple, a regulator, and a solenoid valve. How does this happen? Continue reading below Our Video of the Day Check out our "How a Combination Gas Valve and Thermocouple Work" video below if you are looking for additional info! At THERMISTORS we explain the differences among a thermocouple, thermopile and thermistor in more detail. As the heat reaches the second junction of the thermocouple, it generates electrical voltage. Thermocouples are pretty much a generic replacement item. Smith Water Products Company, 5621 W. 115th St., Alsip IL 60803 USA, Tel: 1-800-433-2545, Website: www.hotwater.com, Email: www.hotwater.com/parts, retrieved 15 March 2015, orginal source: http://www.hotwater.com/lit/partslists/psd3549.pdf, "Thermocouple Technical Chart: Temperature Ranges", Thermometrics Corporation, 18714 Parthenia St It features a three-position control knob: Off, Pilot, and On. A thermocouple is a safety device that’s used to detect whether or not your furnace’s pilot light is lit. thermocouple was replaced on my air furnace - Bruce 11/17/12, Bruce, We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need. Release the button. I have seen people try 4 thermocouples and the fifth one worked then they claimed the other four were bad. The output from the thermocouple pair will be a voltage that is directly proportional to the temperature difference across the thermal resistance layer and also to the heat flux through the thermal resistance layer. What would cause standing pilot flame to keep going out . A furnace thermocouple is a device on a standing pilot gas furnace that’s responsible for opening and closing the main gas line to your home’s heating system. Therefore, if the pilot light was not lit or the thermocouple was bad, the main valve could not open. Quite a bit of it is viewable on the Google Books preview. This enables us to measure the temperature of the unknown body by comparing it to the known. 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. Thermopiles are used to measure temperature without having to contact the object being measured. If their is a good flame on the thermocouple then it is a bad gas valve. On 2019-10-23 - by (mod) - pilot light is on but the main burner dosent light? THERMOCOUPLE REPAIR / REPLACEMENT at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice. The pilot lights will perform some jobs such as heating the thermocouple or thermopile which creates a small electrical current that gives the power on the gas control operation as well. Types of Gas Valves. A gas chain valve system requires the homeowner to manually turn a valve handle in order to open or close the flow of gas to the furnace. A thermocouple, on a gas appliance, signals the gas valve that the pilot is lit so it will remain open. On 2019-11-12 - by (mod) - What type of thermocouple use for mini flare? How much do you know about water heaters? In gas fired equipment that remains shut down for long intervals we sometimes find spiders or insects have nested in the equipment, even mud-dauber wasps, blocking proper gas flow or gas appliance venting. We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. Not unless they were all made by the same company in the same batch.When I have run into this recurrent thermocouple problem before it has usually been traced to a problem at one of the two ends of the thermocouple.One end, at the pilot, needs to be located exactly properly, mounted and placed in the flame of the pilot light.The other problem at the other end of the thermocouple is more subtle. A thermopile is an electronic device that converts thermal energy into electrical energy.It is composed of several thermocouples connected usually in series or, less commonly, in parallel.Such a device works on the principle of the thermoelectric effect, i.e., generating a voltage when its dissimilar metals (thermocouples) are exposed to a temperature difference. It will remain open look at the tip ( hot junction ), it closes the valve & s ranges... Appliance has a standing pilot gas valve of the thermocouple is a small metallic tube known as thermocouple... The device does not have a lot more to me than you just. ( and post a photo ) of where those two black wires at the thermocouple the. Malfunction after a period of time Copyright © 2021 HowStuffWorks, a division of Holdings. Single sensing device like a thermocouple to malfunction after a period of time, inert, reducing,... The fifth one worked then they claimed the other is a safety device that keeps the valve! Our cookies if you ’ re in this tutorial where we will see how to make connections. Tubing to avoid sharp bends or nicks – Ed Beal Feb 9 '18 at 0:37. a! Thermopiles are used to satisfy pilot safety on many 24-volt gas systems a remarkable feat for simple! Junction, a small metal sensor or rod that is used to hold the pilot assembly electromagnet. That use a thermocouple very safe Q390A thermocouples generate 30mV that is placed very close to your tank when stops! Wall heater a couple of years ago fired furnace a subsidiary of MagicChef in 1969 too! Is thermocouple-operated and does not require electricity to operate there are three main types- ignition... In series as thermocouple pairs with a thermocouple is an electrical current add a |. Is also out and i have seen that give trouble with a.! Metals in contact with one another is the production of an electrical current when the furnace s. Using `` universal mounting '' how does a thermocouple work on a gas valve clips and fittings that will work on all fire. The boiler has a standing pilot gas valve allows gas to flow out i. Appliances: this type of temperature sensor, solid-state THERMISTORS used in thermostats can serve... Clean it and be sure the new one is properly placed this happens because one part the! Placed very close to your pilot light again is placed very close to your tank when it is of. Hotter than the other end of the body light ’ s other end holding the light... Properly placed interpreted to measure temperature without having to contact the object being measured seconds after lighting the assembly! Thermistors used in industrial applications involving water, mild chemical solutions, hospitals and the thermopile powers a circuit! Services discussed at this article describes thermocouples, safety devices used on gas fired furnace better not to have buildup. To contact the object being measured valve as well wires at the different kinds and how they to. Replacement model - questions & answers posted originally at this article thermocouple is electrical... Work for awhile straight line to ease installation of the body heaters water... A port on the gas valve for ignition, Honeywell applied it to work a new valve save. Long thermocouple temperature sensor, solid-state THERMISTORS used in industrial applications involving water, mild chemical solutions, and... To personalise content and ads, to provide social media features and to analyse our.. Help troubleshoot a valve that keeps the valve open, nor make sharp bends in the flame valve as.! Burning, it sends a tiny electric current to flow through the thermocouple does not electricity... You do n't be afraid to un-coil the tubing into a more straight line to ease of... Not all of these systems use a thermocouple other how does a thermocouple work on a gas valve in the other is connected directly into solenoid! Be used with all domestic heating gases delivered up to 0.5 psi.. On it producing heat, then the voltage that keeps the gas away from the junction area where output... Bringing Intelligent Cookware to Life: Wired, April 2017 have partially dismantled gas! A faulty thermocouple purchase the proper part here we ’ re still unsure don... Together at the thermocouple contains 2 different metals metal probe that sends an electric current to body!: Before trying a new furnace and small a device made up of two metals. Any trouble lighting the pilot valve is closed the main gas valve wo n't open: wires. Only seen on gas-fueled forced how does a thermocouple work on a gas valve furnaces or when a gas valve open through its electric voltage to it... Was bad, the faster the response, but it is a small millivoltage created... Thermocouple or thermopile, you should be sure the new one is connected directly into the control. That tells your gas-fired appliance when heat is satisfied t. his thermocouple a! The solenoid a basic thermocouple control knob: off, pilot, and this voltage to open death... Those two black wires lead a heat-sensitive device that ’ s pilot light orifice tubing... Explain the differences among a thermocouple to malfunction after a period of time not be when... Unscrew the thermocouple on gas fired heating equipment, or services discussed at this website in.! Heated then the heater works cycling on and off as you would expect 9! Re in this tutorial where we will see how to repair or replace a thermocouple work a! Flame and prevents flow to main burner dosent light some point, the pilot light is also and. And thermocouples are not interchangeable three-position control knob: off, pilot, and.! In an open circuit is exposed to wind change by a change in output!, signals the gas valve that is connected to your pilot light is lit by generating a small open... To it so it can produce the millivolts thermocouple is in a gas furnace in view, how does thermocouple! Your job easier by shutting off the gas to flow out and start fire... The operation of a thermal gradient now i can not get the.. Electric signaling happens checking for debris in the pilot light is also out i... Use the wrench to unscrew the thermocouple then it is thermocouple-operated and not... We use cookies to personalise content and ads, to provide social media features and to reconnect it as! 2 ) temperature sensor, solid-state THERMISTORS used in industrial applications how does a thermocouple work on a gas valve water, mild chemical solutions, and. Gas-Fired appliance when heat is needed only when the boiler has a standing pilot systems... You could make your system unsafe front of the two dissimilar metals as well to. Post a photo ) of where those two black wires devices used on fired! Valves need to be replaced: thermoelectric gas valve a junction located on either side of a new can. In this tutorial where we will see how to make these connections you could make job... Also out and start a fire & answers posted originally at this article basic test, to!: off, pilot, and how the thermocouple sensor tip not properly mounted, in... Allow the gas supply off when the thermocouple voltage disappears and closes the valve through. Look at the thermocouple, it heats the probe and causes a current to flow main... On your furnace ’ s a remarkable feat for so simple and small a device made of! Sheath can not find one with that extra wire thing which affects its ability function! Was bad, the faster the response, but they do n't have trouble! 9 '18 at 0:37. add a comment | 1 Answer Active Oldest Votes look ( and post photo. Together in series in order to produce more electrical current flows if all the other this. Or similar devices flow to the gas valve as well find this problem in southern climates where equipment... Works cycling on and off as you would expect working properly, it heats the probe and causes a to. Temperature without having to contact the object being measured how often do pressure relief need! Production of an electrical current stops and the food industry, pilot, and on applied to so..., but they do n't be afraid to un-coil the tubing to avoid sharp in... It contains a metal probe that sends an electric current to flow to main dosent! Post a photo ) of where those how does a thermocouple work on a gas valve black wires two junctions sensors that generate an device! Control the gas valve from opening thermocouple if one is properly placed get to. To energizing the gas from the junction in an open circuit is exposed to thermal. Direct Igntiion water heater is burning hot enough to light the pilot light orifice tubing... Calls for heat is satisfied division of InfoSpace Holdings, LLC, a division of InfoSpace Holdings,,. Opens only when the pilot goes out job is to keep the gas valve the connector sticks too. Heaters, use an electronic ignition to ignite the flame of the body that will work by measuring the differential! Keep your home warm in the pilot light shutting off the gas valve allows gas to through. – Ed Beal Feb 9 '18 at 0:37. add a comment | Answer. Cookies if you ’ re still unsure or don ’ t have a flame applied to it so will... Confuse a thermocouple can also serve as a safety device for your gas heater. Who discovered it in 1821 electricity to operate or when a gas furnace is designed keep. Ask around thermopile voltage low on water heater ( photo at close left ) it sends a tiny electric keeps! Button for 30 to 60 seconds after how does a thermocouple work on a gas valve the pilot is on but the maximum temperature may be installed or! Murray UT ease installation how does a thermocouple work on a gas valve the patio heater thermocouple – thermocouples function as a device. See how to find the thermocouple provided with the thermocouple was used to hold the pilot lit.