A natural gas furnace is one of the most economical and energy-efficient ways to heat a home or commercial building, and most natural gas furnaces are extremely reliable. Unfortunately, they can still suffer from malfunctions from time to time, and the gas ignition system inside a natural gas furnace is one of the more common points of failure.
Different types of gas furnaces use various ignition systems, and each type of ignition system can suffer from its own unique problems. Here are three of the most common causes of ignition system failure in natural gas furnaces, and what you should do if you encounter them:
Cracked HSI System
Hot Surface Igniters, or HSIs, are small, rod-shaped ignition systems commonly used in gas furnaces. When activated, an electrical current is passed through the igniter, causing it to quickly become red hot and ignite the surrounding gas inside the furnace combustion chamber.
With time and use, the strong electrical currents that flow through HSIs can cause them to become damaged and cracked, and they'll eventually stop functioning. The naturally present oils on your hands can speed up the cracking process, so you should make sure not to touch the HSI while you are maintaining your furnace.
If your furnace fails to ignite because of a cracked HSI, you should notice that the igniter fails to glow when your furnace is powered on. You may also be able to see visible damage on the HSI's surface. Fortunately, these igniters are relatively cheap and easy to replace. Call in a heating repair service to handle HSI replacement if you do not know how to replace it yourself.
Intermittent Pilot Failure
Intermittent pilot systems generate electrical sparks to ignite the natural gas inside your furnace's combustion chamber. These sparks should be generated automatically when your furnace is activated by the thermostat.
If your intermittent pilot-equipped gas furnace does not ignite when needed, take a look through the combustion chamber's inspection window. The sparks generated by intermittent pilots are usually visible, so if you don't see a spark when the furnace is activated, the electrical wiring that provides power to the pilot may have failed.
Intermittent pilot failure can be caused by age and wear and tear, and can also occur if the pilot becomes waterlogged due to excess condensation. This is more likely to occur in high-efficiency gas furnaces, which create more condensation by-products than standard models. Have the intermittent pilot professionally replaced to get your furnace back up and running.
Clogged Standing Pilot
Older gas furnaces may be equipped with standing pilot lights. These are small flames that burn constantly, and automatically ignite natural gas when the furnace is activated. These tiny flames create a considerable amount of soot. If too much soot accumulates inside the pilot's gas supply line, it may go out.
If your malfunctioning furnace has a standing pilot, but you cannot see a small flame burning inside the combustion chamber, it is probably clogged and will need to be professionally cleaned or replaced. However, replacing your standing pilot-equipped furnace with a newer model may be more cost-effective, as these outdated furnaces are much less efficient than furnaces equipped with intermittent pilots or HSI systems.
For further assistance, contact local heating services.