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Why Is My Furnace Going “Boom?”

No gas furnace will ever run silently, but some noises signal a problem with the components. If your furnace makes a boom, bang, or popping sound whenever it starts up, the equipment is telling you it needs some TLC as soon as possible.

What Is Making That “Boom” in My Furnace?

A gas furnace that booms, bangs, or pops when it first turns on has a problem called delayed ignition. This issue typically occurs when you haven’t used your furnace for a while or if the equipment is overdue for maintenance. Here is what happens:

  1. Your thermostat signals your furnace to start up.

  2. The gas valve opens.

  3. The released gas goes to the burners.

  4. The gas is supposed to ignite immediately. When it doesn’t, this problem is called delayed ignition.

  5. Because the gas doesn’t ignite right away (for reasons we’ll discuss below), it builds up inside your furnace. As you can imagine, a buildup of flammable gas is bad.

  6. At some point, the gas will finally come into contact with a flame from the burners and ignite in a small explosion. The “boom” you’re hearing is that explosion.

Why Is Delayed Ignition a Problem?

Delayed ignition can create safety hazards and lead to costly repairs. For instance, if you need to relight the pilot light, extra gas in your furnace can cause a flash fire that can burn you and even lead to a house fire.

Repeated explosions can also cause your heat exchanger to crack. This is one of the most expensive furnace parts to repair. Plus, a cracked heat exchanger allows carbon monoxide and other toxic gases that would usually be vented outside to enter your home’s air supply.

What Causes Delayed Ignition?

Multiple problems can cause delayed ignition. This is why it’s best to get a professional to diagnose the root of the issue. Many times, the equipment is merely overdue for maintenance, and the burners only need to be cleaned or realigned. A dirty or faltering pilot light can also be the culprit.

Other ignition problems involve the gas itself, which is actually a combination of natural gas and air. If not enough gas is supplied to the burners or too much air is in the mixture, the gas-air mixture will struggle to ignite.

Corrosion can also lead to ignition issues. When your furnace goes through a period without use, moisture can build up and cause the furnace’s firebox to corrode. The corrosion build-up can hinder gas from getting to the burners.

At Premier Indoor Comfort Systems, LLC, our thorough technicians are dedicated to helping you solve your home’s heating system issues. For heater repairs in Whittier, North Carolina, and Canton & Tyrone, Georgia, give us a call at (770) 268-2422 or contact us online.