Condensing gas furnaces, also known as high-efficiency furnaces, are prized for their low running costs, and can effectively heat your home using very little natural gas or propane. Unfortunately, like any other type of furnace, they can still suffer from mechanical problems.

If your condensing furnace is not producing any heat, the problem may be caused by faults with your furnace's hot surface igniter (or HSI). 

How Do Hot Surface Igniters Work?

Modern condensing gas furnaces do not use pilot lights to ignite the gas entering their combustion chamber, and rely instead on electronic ignition. Some models use ignition electrodes that create sparks to ignite the gas, but the most commonly used ignition devices are hot surface igniters.

These igniters function by passing an electrical current through a metal or ceramic rod, creating electrical resistance that rapidly heats the rod to very high temperatures. The simplicity of this design means that HSIs are generally very reliable. However, they can still malfunction, preventing the rod from heating up to ignite the gas and leaving your condensing furnace unable to generate heat.

Why Do Hot Surface Igniters Malfunction?

Passing electrical current through a hot surface igniter stresses its structural stability, and after several years of frequent use, an HSI will start to crack and crumble. Electrical current cannot pass through a cracked HSI evenly and may prevent it from getting hot enough to ignite the gas in the furnace's combustion chamber.

Cracked HSIs are inevitable if you use your condensing furnace for many years, but they are more likely to crack prematurely if handled improperly. Oils on your skin can transfer to the surface of the igniter, causing the surface of the igniter to heat unevenly and making cracking more likely. Caked-on dust and soot can cause similar problems.

Damaged or faulty electrical wiring can also cause your condensing furnace's HSI to fail. If the electrical current to the HSI is broken by frayed or disconnected wiring, it will not heat up when the furnace is activated, preventing gas from igniting.

How Can You Tell If A Hot Surface Igniter Has Failed?

Different condensing furnace models have HSIs placed in different locations. In most models, the HSI is located directly over the intake vent that funnels propane or natural gas into the furnace's combustion chamber. You may be able to spot it yourself through the combustion chamber's inspection hatch.

If the HSI is visibly cracked, or is coated in a thick, uneven layer of soot or dust, a faulty HSI is probably causing your problems. You can attempt to clean a dirty HSI yourself, but bear in mind that accidentally touching the HSI while cleaning it will do more harm than good. 

If the HSI has failed due to faulty wiring, the damage will not be visible. 

What Should You Do About A Faulty Hot Surface Igniter?

If your condensing furnace is not generating heat, and you suspect a faulty HSI is to blame, you should call in a professional furnace maintenance and repair service as soon as possible. These services can quickly and efficiently replace cracked HSIs and clean dirty ignition surfaces without causing accidental damage. 

If the HSI has failed due to faulty wiring, repair services can detect the problem using multimeters, which will measure the electrical current (or lack thereof) passing through the igniter. Any damaged wiring can be replaced quickly and inexpensively, getting your condensing furnace back up and running quickly. 

For more information, reach out to a company such as Paris Heating and Cooling.