Hot Surface Ignitors
As furnaces have advanced, the old standard pilot light system has gone the way of the Dodo, giving way for
advanced technologies. Many modern furnaces use hot surface ignitors, or HSIs. Essentially, the HSI's function
resembles that of a light bulb, only in this case the product isn't light but heat. A thermostat calls for
heat, causing electricity to pass through the ignitor until it glows red hot, at which point it lights the
Types Of Hot Surface Ignitors
Hot surface ignitors are either made of silicon carbide or silicon nitride. Essentially, silicon carbide models
are older versions, and silicon nitride are the modernized version, the main variation being durability.
Estimated in some circles to be seven times more durable than silicon carbide, a silicon nitride ignitor uses
modern and more advanced ceramic technology. Silicon nitride ignitors are also considerably more energy
efficient, using less than half the energy to power them as required by the older silicon carbide ignitors.
Replacing Or Repairing A Hot Surface 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. Estimates vary on silicon nitride, with some
saying twice as long, others saying as much as seven times as long. Considering that the part is continually
getting hot and cold, it seems unlikely that the part will last 20 to 30 years, particularly since 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'll 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 to the carbide setup.
Who Makes Replacement Hot Surface Ignitors?
There are many companies that make replacement ignitors, most prominent among them being Robertshaw, Uni-Line, or
White-Rogers, which says its Universal Nitride Ignitor Upgrade Kit can replace virtually all silicon carbide
systems in the field. Other companies making HSIs include: