Therefore, inspecting and testing your thermocouple should be part of your furnace maintenance. Be sure to inspect before you test, however, to ensure that there are no obvious problems that could affect the readings from testing! The thermocouple is a small electrical device, but it is a critical safety component on your furnace. 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.
You will need a wrench, multi-meter, and a flame source, like a candle or a lighter, to perform the test. What does a thermocouple look like and how do you find it? Its copper tubing makes it easy to spot.
The thermocouple is made up of a tube, a bracket, and wires. The tube sits above the bracket, a nut holds the bracket and wires in place, and underneath the bracket, you will see the copper lead wires that connect to the gas valve on the furnace. Once you have located the thermocouple, do a visual inspection. You are looking for a few things. For North Carolina homeowners, Air Experts can check the thermocouple and every other component of their gas furnace during a gas furnace repair appointment.
Call Air Experts at or contact us online today to schedule furnace repair service! The technician was right on time, diagnosed the problem quickly and was able to repair the issue. Very satisfied with the service. They are available online and in home supply stores for a reasonable cost. The length and the thread type are the two concerns when purchasing one. The thermocouple looks like a piece of metal tubing smaller than a soda straw.
To find it, first locate the gas control box. This is the box that the main gas line enters, where you turn the gas on in the furnace. The other end of the thermocouple sits in the flame of the pilot light. It matters, because thermocouples are DC, so there is a polarity. To install the thermocouple temperature sensor of a pyrometer, you can either use a drilled peephole plug or drill a hole in the kiln wall. While the kiln is still cold, insert the plug into the peephole.
Thermocouples are polarized and will not give an accurate reading if the leads are switched. Thermocouples can last several years, but they don't typically last as long as the furnace itself. If the pilot remains lit, but the main furnace doesn't stay lit, it's time to replace the thermocouple.
Replacement thermocouples are in stock at most hardware and home improvement stores. A thermocouple TC is a temperature sensor. It reads the temperature in the kiln and gives the information to the DynaTrol or pyrometer. A TC is made from 2 different metals. The DynaTrol can translate the millivoltage signal into a recognizable temperature.
If you are set on replacing the thermocouple yourself , here are a few things to keep in mind. Locate the thermocouple next to the pilot light and disconnect the unit by removing the copper lead. Unscrew the gas line connection nut AND bracket nut holding the thermocouple in place. Before the test, turn off the gas supply because you must first remove the thermocouple. 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. Without a thermocouple , it will seep tiny bits of gas into the combustion chamber of the device.
In a few hours, it can leak enough gas for a small explosion, probably just enough to shorten your eyebrows. What is the life expectancy of a thermocouple? Through a mutual investigation, we focused on the replacement frequency of the protection-tube assembly, which contained both a primary and secondary alumina protection tube.
In this scenario, placing the brand-new element in the used protection-tube assembly Fig. Depending on how contaminated the used assembly was, the accuracy and longevity of the new element was negatively affected at an accelerated rate.
The infrequency of replacement resulted in immediate contamination of the new thermocouple element Fig. In this scenario, the perceived savings of the protection-tube replacement protocol resulted in significant loss due to reduced thermocouple life, accuracy and product quality. There are a host of parameters that end users need to know up-front when considering expected thermocouple life. These include:. Smaller-diameter sensors react more quickly but are also consumed at a faster rate.
A steady temperature will enjoy longer life, a cycling thermocouple will see shorter life and higher temperatures degrade a thermocouple more quickly. These are just a few of the operational factors that must be considered. Additionally, environmental conditions also impact thermocouple selection.
Platinum-based also known as noble-metal sensors such as Type R, S or B can be very accurate over an extended period if properly protected.
Noble-metal thermocouples inherently have a very low EMF electromotive force output, however. Even the slightest contaminant may influence the microvolt output of the sensor, thereby altering the readings.
Even the geographic furnace location in terms of elevation above sea level has a minute but measurable effect on thermocouple output. For example, a Type-J thermocouple element contains an iron leg that may become oxidized at higher temperatures. We all want to know how long our thermocouples should last, but the attention to detail is critical. As a designer and manufacturer of the thermocouple, this means we need a very careful and thorough review of all the operating parameters, even the host of tiny details that may seem innocuous or insignificant.
Customers are demanding improved accuracy, longer life, stringent quality and strict adherence to specifications. The only way to stay ahead of this industry-wide consistent pursuit is to collectively and thoroughly understand the operating parameters. In an ideal environment, that length of time can be indefinite. But as reality dictates, particularly in thermal processing, that is not necessarily the case.
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