Maintaining Your Furnace - Inspect Your Hot Surface Igniter


Unlike older model gas furnaces that use a standing pilot light to ignite the burners on the furnace, many of today's modern models use an electronic ignition system. This includes a Hot Surface Igniter (HSI), sometimes referred to as a glow plug or glow stick. Electricity passes through the silicon carbide igniter, making it glow red hot. These newer, more efficient models, made in the past 10 years, are replacing the old gas pilot furnace models.


When the thermostat calls for heat, the HSI receives an electrical current which heats its surface.  The igniter glows red and then lights the burners in the gas furnace.  Over time, the igniter is continually getting red hot and then cooling, creating stress on the element.  Because of this, igniters have a 3-5 year life expectancy.  They will eventually crack and need to be replaced.


If you suspect that you have a damaged HSI, you will most likely be able to change the part yourself.  Like a light bulb, they are a regular replacement item.  However, there are several things to consider before tackling this job on your own.


First, visually inspect the HSI for cracks or white spots on the carbide section. Cracks are not necessarily visible.  Though the igniter may be cracked, it may still be working, but with a shorter remaining life span.  If you see a crack or white spot, the igniter should probably be replaced. 


It is important that the correct, original manufacturer's igniter be used in the repair. There are many igniters on the market; however, many do not have the correct voltage or warm-up time as the original design.


HSIs are made of a very brittle material and will break easily.  Igniters can be damaged during transit or installation.  While working with this fragile component, it is extremely important that you do not bump the carbide section against metal.  Take care not to touch the carbide surface because the oils from your hands can permanently damage the element.  Use patience and caution throughout the replacement process.


Once the new HSI has been installed, check for functionality.  Have the thermostat call for heat.  After a few seconds, the igniter should glow red and light the main burners. 


It is always a good idea to have your furnace checked regularly, by a qualified service professional, for optimum performance, efficiency and safety.



Richard F. Pezzino is a licensed and insured real estate inspector and owner of Accu-View Property Inspections.  He has more than 25 years experience in both residential and commercial real estate.  Information available at 716-882-2200 or  NYS License #16000005200.