Thermocouples: Why You Need Them And What Can Go Wrong
If you're old enough, you probably remember needing to ignite pilot lights on your gas appliances. Everything from stoves to furnaces used this ignition method, which relied on a continuous flame to ignite the main burner when necessary. Pilot lights were a straightforward and relatively reliable ignition method, but they were also inefficient and occasionally needed maintenance.
Of course, if you subscribe to the theory that "if it ain't broke, don't fix it," you may still have a standing pilot furnace in your home. Standing pilots use a safety device known as a thermocouple, and if you have this type of furnace, it can pay to understand how it works and when it may need repair.
Why Do You Need a Thermocouple?
Gas burners all work the same way. Natural gas flows down a pipe and through an orifice, where it encounters an ignition source. The ignition source provides heat that ignites the gas when combined with the surrounding oxygen. Gas appliances rely on complete combustion to operate cleanly and safely since unburnt fuel can potentially enter your home and create a hazard.
The pilot light provides the ignition source for the main burners on old-style furnaces. As long as the pilot stays lit, any gas that passes over it will quickly ignite and can provide heat for your home. However, this method of operation means that the pilot light must stay lit at all times so that it's ready to go whenever your thermostat calls for heat.
A continuous flame requires continuous fuel, which can be a potential hazard. If the pilot light goes out for any reason, the pilot light orifice may continue to leak unburnt gas into your home. The thermocouple is a safety device that prevents this situation. If the thermocouple doesn't detect the heat of the pilot flame, it shuts off the gas supply to avoid a small but steady leak.
What If Your Thermocouple Fails?
Thermocouples are simple sensors that generate a voltage based on heat, but they can fail due to wear, age, or excessive amounts of soot and debris. A failed thermocouple will usually cause your pilot light to stop functioning, preventing your furnace from heating. If your furnace suddenly stops working, an excellent first step is to check if the pilot light is out and will not relight.
Remember that the thermocouple is a critical safety device you should never bypass, particularly on older furnaces that may already be operating inefficiently. You can clean your thermocouple as part of a regular maintenance routine, but this won't necessarily extend its life indefinitely. These devices tend to fail eventually, especially on old furnaces well beyond their expected lifetime.
If you suspect a problem with your thermocouple, it's a good idea to have an HVAC technician investigate. They can replace the sensor if necessary while also checking for any other problems that may cause efficiency or safety issues with your aging furnace.
For more information on furnace repair, contact a company like IMS Heating & Air Inc.