Silicon Carbide Ignitors

Ignition mechanisms for furnaces have evolved in recent years. Chances are fairly good that your current furnace has a silicon nitride ignitor in it, which is a modernized, more durable version of the old silicon carbide ignitors. The function remains the same, to answer a thermostat's call for heat. When the thermostat requests heat, electricity passes through the ignitor until it glows red hot, at which point it lights the burners.

Strengths And Weaknesses Of Silicon Carbide Ignitors

The strengths of silicon carbide igniters are really the same as those of silicon nitride ignitors, aside from durability, which really necessitated the conversion from carbide to nitride for the product. While ignitor shapes are different depending on the furnace, the actual composition and functionality are the same. When introduced in the early 20th century, silicon carbide provided an upgrade from metallic heat units, offering increased operating temperatures, though at the beginning this impact was somewhat minimized by the use of water-cooled terminals, which were assigned the task of transporting electric current to the silicon carbide-based hot zone. This is because the terminals weren't attached to the zone itself but rather were held by springs or weights. The process evolved until the 1960s, when one-piece elements were introduced. Ultimately, this yielded high-density, reaction-bonded elements that offered added resistance to chemical wear and oxidation. When silicon nitride ignitors came into the picture, they offered all the strengths at enhanced durability--as much as seven times, according to some professionals--rendering carbide, while not obsolete, a far lesser-used option.

Replacing Or Repairing A Silicon Carbide Ignitor

Referring to the earlier light bulb analogy, these parts are basically replacement items. Consensus is that a silicon carbide ignitor will last between three and five years. Considering that the part is continually getting hot and cold, many professionals recommend keeping an extra part on hand just in case it blows in the middle of the night or during a drastic cold snap. There are many different designs in terms of appearance for the ignitors, but they are largely interchangeable if they will fit in the furnace space available. It used to be that carbide ignitors were unable to be replaced by nitride models, but that has since been remedied with the mass approval of the nitride component. As such, many universal nitride parts come with adapters so they fit the carbide setup. Because silicon carbide is such a sensitive compound, these ignitors must be handled with extreme caution, as they are greatly impact-resistant.

Who Makes Replacement Silicon Carbide Ignitors?

White-Rodgers makes a thorough line of silicon carbide ignitors--more than 20, depending on the connector type and lead length. According to White-Rodgers' compatibility list, there are more than 40 companies making silicon carbide ignitors, including but not limited to Amana, Coleman, Ducane, Heil, Hupp, Norton, RobertShaw and Trainco-Heatmaker.