Silicon Nitride Ignitors
Silicon nitride ignitors are the widest-used ignitors in gas furnaces because of their extended durability.
Silicon nitride is a hard solid, formed through the direct high-temperature reaction between silicon and
nitrogen. Silicon nitride is so durable that it's found only in meteorites. With a melting point of 1,900
degrees Celsius, silicon nitride is a perfect component for use in ignitors, which answer a thermostat's call
for heat by sending electricity through the thermostat until it glows red hot, at which point it lights the
burners.
Strengths And Weaknesses Of Silicon Nitride Ignitors
Silicon nitride offers a series of benefits that make it ideal for use as an ignitor component. The compound
provides strength over an extensive temperature range and is extremely hard and fracture resistant--the chief
aspects of its durability. Silicon nitride is also strongly resistant to thermal shock and chemicals. There are
two differences between between the weaknesses of silicon nitride and
silicon carbide, neither of which is
considered significant for the purposes of an ignitor: One, the melting point is actually lower than that of
silicon carbide (which doesn't melt until 2,300 degrees Celsius), but it's a temperature ignitors won't
reach. The second, is that it's a more costly compound than silicon carbide. However, the increased durability
means fewer replacements, offsetting the cost, with estimates varying from twice the life of silicon carbide
products to seven times the durability.
Replacing Or Repairing A Silicon Nitride Ignitor
If estimates are to be believed, you can conceivably go between 10 and 25 years without ever needing to change a
silicon nitride ignitor. However, if you do, the process is quite simple. Select your ignitor (there are
connector codes, depending on manufacturer) by looking at the one you have and comparing it to a store's stock
or any one of several online charts of HSI appearances. Note that if you don't find the exact base and connector
combination, ceramic wire nuts are usually included to help adapt the new kit to the old setup. There are many
different ignitor designs, but they're largely interchangeable if they'll fit in the furnace space available.
It used to be that carbide ignitors couldn't 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.
Who Makes Replacement Silicon Carbide Ignitors?
Most companies that make furnaces also make components, such as ignitors. However, a company called Glo-Stix sells
a universal hot surface ignitor kit that includes the silicon nitride igniter, leads, two terminals, a universal
mounting bracket and an instruction booklet. This kit is said to replace more than 100 units on furnaces, as well
as boilers and water heaters. The part number is HSIURK120V.
