I can remember the days of my childhood when my father struggled every winter to keep the pilot light up and going each day. The pilot light was a small flame that needed to stay lit in order for the gas element to fire up when the thermostat signaled for it to fire. Without this thermostat it would be impossible for the gas burner to ignite. Some of the other gas appliance such as the hot water heater and the stove worked under the same principle. We are fortunate today to have a hot surface ignitor that makes it much easier to ignite the gas burners we need. We will take a look at a hot surface ignitor to see what it is and what it does.
Most modern furnaces and boilers today are equipped with the hot surface ignitor. These ignitors are used to light the gas flame when the unit is ready to ignite. Most of the older igniters are made of Silicone Carbide while the newer models are constructed from Silicone Nitrate. When the ignitor is signaled it will glow red hot, this red hot glow is a high temperature glow that ignites the fuel. The Silicon Carbide ignitor will usually last up to five years under normal use. The Silicon Nitrate will last longer. Over a period of time these ignitors will eventually need to be replaced. Most of the ignitors are universal as long as they will fit the furnace space that is provided for the ignitor and a large number of replacements can be found at HVACRsupplyNOW.com these ignitors can fail at any time and it’s always a good idea to have a spare one available at all times.
If your ignitor fails to ignite your system, you will need to inspect the ignitor to see if this is the root of the problem. The very first issue is to check to make sure the wires supply current to the ignitor are secure. Sometimes these wire connectors will vibrate loose or the connectors could develop a burn spot or burn completely apart from the connector. If the wires are still connected securely then you will need to inspect the ignitor to see if it may be cracked or may have developed a hot spot. If there is a hot spot on the ignitor the current will not complete the circuit allowing the ignitor to fire.
If you cannot still determine why the ignitor is not firing, you will need to check the location where the wires are connected to see if you are getting a voltage reading. At the startup of your unit you should receive a reading of 115 volts. If you have that reading at the wire connectors your ignitor is not firing. A hot surface ignitor resistance can be checked with the multi meter. An ignitor uses resistance to fire much like a light bulb to glow in order to light the gas.