Where is thermocouple located on furnace

Get out of the house, leaving the door open, and immediately call the gas company or the fire department to report a leak. Do not re-enter your home. Most natural gas furnaces have few operational difficulties. Problems typically involve the pilot light, the thermocouple, or some part of the electrical system. On some gas furnaces and heaters, a plug-type door covers the pilot light assembly. To gain access to the pilot burner, pull the door out of the furnace housing. On other units, remove the panel that covers the pilot and gas burners.

The pilot light controls, reset buttons, gas valves, and thermocouple are usually contained in an assembly at the front of the furnace. The furnace limit switch is located on the plenum main chamber or main duct junction on the upper housing of the furnace. Now that you're ready to fix your furnace, save some time by identifying exactly what's wrong with it.

Look for your problem, and solution, on the handy chart on the next page. For more articles on home repair, check out the following links. Furnace Maintenance : Save yourself time and money by learning the steps to keep your furnace in prime condition.

Major Appliance Repair : If the furnace isn't the only thing in your house on the fritz, you can learn how to fix other machines in this article. Small Appliance Repair : Once you've tackled the furnace, a toaster or blender seems like child's play. Find out how to fix them here. Thermostat Maintenance : To make sure there's actually a problem with your heating system, you may want to check the thermostat, too.

Learn how to calibrate a thermostat. Troubleshooting Gas Furnaces and Gas Heaters There are many potential reasons that a furnace might not be working, but fortunately, many of the solutions are as easy as pressing a button. Use this chart to fix a wide range of conditions that prevent your furnace from working. If instructions for relighting the pilot are not provided, follow this general procedure: Step 1: Find pilot light assembly.

It typically has a gas valve with on, off, and pilot settings. Step 2: Turn valve to off and wait three minutes. Step 3: Switch valve to pilot setting.

Hold lighted match to pilot opening while you push reset button on pilot control panel. Keep this button depressed until pilot flame burns brightly, then set valve to on position. Step 4: If pilot flame won't stay lit, opening may be clogged. Turn gas valve off, and clean opening with piece of fine wire.

If it won't stay lit after several attempts, you may have faulty thermocouple. If pilot flame still won't stay lit, call professional service person. Some furnaces have an electrical system to ignite the gas; in these systems there is no pilot light. 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 feed valve, the thermocouple is probably bad.

A thermopile looks like a thermocouple, and does a similar job - sensing temperature, such as a gas flame to function as a safety device. Watch out : thermopiles and thermocouples are not interchangeable.

When replacing a temperature sensing device like a thermocouple or thermopile, you should be sure to purchase the proper part. Thermopiles are made by combining multiple thermocouples together in series in order to produce more electrical current than a basic thermocouple.

Externally a thermopile still looks like a single sensing device. 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. Watch Out : Proper selection and installation of a thermocouple is important for the device to function safely, or for that matter to function at all.

The manufacturer of the heating appliance in which the thermocouple is used will provide installation instructions that must be followed for safe, reliable use of the heating appliance.

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. 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. The thermocouple is provided with the connecting tubing coiled neatly in a package.

Don't be afraid to un-coil the tubing into a more straight line to ease installation of the device. But do not nick, kink, nor make sharp bends in the tubing. Typical thermocouple installations include instructions for bending the tubing to avoid sharp bends or nicks. Watch out : don't modify a thermocouple other than gentle bending as described in the installation instructions.

For example do not try to cut or trim the length of the thermocouple. Doing so will almost certainly make it inoperative and thus unsafe. 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. Take care not to damage the igniter wire and to reconnect it just as it was.

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.

You can make your job easier by shutting off the gas supply and removing the old thermocouple intact to help select a replacement model. Replacement thermocouples using "universal mounting" include clips and fittings that will work on most gas fired heaters and water heaters. For example Sid Harvey's Dyna-Couple universal mounting thermocouple, sold in lengths from 18" to 48" will replace Honeywell, Robertshaw, Penn Baso, White-Rodgers and other thermocouples. Doing so risks fire, explosion, injury, even death.

How to Troubleshooting Thermocouples on Gas Fired Heating Equipment First confirm that the problem is the thermocouple Typically the gas control is pushed-in or held in a spring-loaded position to force gas through the pilot light assembly to permit manually lighting the pilot flame. If you are able to light the pilot on the gas fired appliance but when you release the gas control from it's "LIGHT" position the pilot immediately goes out, if there was a good solid flame that was clearly touching and heating the thermocouple, that is, the thermocouple was properly positioned in the pilot flame, and if you are sure that you held the control in the LIGHT position long enough for the thermocouple to heat up normally 30 seconds is plenty , then I suspect that the thermocouple is defective.

Watch out : Before trying a new thermocouple I'd suggest checking for debris in the pilot light orifice or tubing. 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 have run into this problem and also read other accounts of it concerning the Gaffers and Sattler Model S 80 FDF gas fired furnace and similar gas fired heating equipment but this debris clog problem is widespread and may show up on just about any pilot-lit gas fired appliance, even gas log fireplaces and portable heaters.

Gaffers and Sattler was an appliance brand kitchen ranges, heating equipment, air conditioning owned by Maytag and actually preceded "Maytag" as a company name. Magic Chef found its way back to Maytag in If you are looking for parts for Gaffers and Sattler equipment check with Maytag. Check for debris blockage right at the pilot light, inside the gas tube between the pilot light and the gas control valve, and using a fine wire don't scratch or enlarge the orifice try cleaning the orifice at the pilot light itself.

What would cause standing pilot flame to keep going out. Remove the thermocouple by unscrewing the copper lead and connection nut first and then the bracket nuts. Next, take your meter and set it to ohms. Take the two leads from the meter and touch them—the meter should read zero. Once this check is done, turn the meter back to volts. For the actual test, turn on your flame source, and place the tip of the thermocouple into the flame, leaving it there until it is quite hot.

Next, attach the leads from the multi-meter to the thermocouple: put one on the side of the thermocouple, and attach the other lead at the end of the thermocouple that sits in the pilot light. A working thermocouple will give a reading of between 25 and 30 millimeters.

If the reading is less than 25 millimeters, it should be replaced. Read Full Testimonial. Discover the Difference. Leave Us a Review on Google. This doesn't have to be precise—it just helps to start with a similar shape.

Connect the new thermocouple to the pilot burner assembly bracket, tightening the nut s until it's just snug. Be careful not to overtighten. Thread the end fitting of the thermocouple into the gas control valve and tighten it by hand. Then, use the open-end wrench to tighten it about a quarter-turn more; again, do not overtighten. Turn on the gas and electrical power to the furnace. Replace the furnace access cover and test the furnace operation by changing the thermostat settings to make sure the furnace turns on and off properly.

If the furnace has been running, wait at least 30 minutes for the flame sensor to cool completely. Confirm that the flame sensor is removable—if so, it should be fastened to the burner assembly with one or more screws. If the sensor is integral to the gas ignition system, you'll need to call a professional furnace technician to make the repair. Disconnect the electrical wire leads to the sensor.

Disconnect the other end of the leads at the control box. Remove the flame sensor by loosening the fastening screws with a nut driver or wrench. Install the new flame sensor in the same position as the old part and secure it with the screws. Reconnect the electrical leads to the sensor and to the control box.

Test the furnace to make sure it turns on and off properly. Emergency Management and Communication. City of Chicago Utilities. Actively scan device characteristics for identification.