Why is my gas furnace making a scary 'boom' noise?  Pippin Brothers, Lawton, OK
October 28, 2014

Do you hear a 'boom' from your furnace when it starts up? Please don't ignore it!

Your furnace is most likely experiencing "delayed ignition." This can severely damage your furnace and burn you if you're not careful.

What is delayed ignition?

When your thermostat calls for heat from the furnace, a gas valve opens, sending gas to the furnace's burners to ignite the gas.

(Side note: Here's a simple video on how your furnace works)

Delayed ignition is when that gas isn't ignited immediately, allowing the gas to build up in the furnace. The gas keeps building until--BOOM--it reaches a flame and finally ignites, causing a small explosion in your furnace.

Imagine being in a room filled with gas and someone decides to light a match or you turn on the burners to your gas grill and hesitate a moment before pushing the ignite button. Yeah, it's like that.

What's causing the delayed ignition?

There are a variety of possible issues, all of which need a professional technician to solve.

But if you want to learn the lingo, delayed ignition can be caused by:

Too much primary air-- Primary air is the air mixed with the gas before it's ignited. Too much primary air makes the gas-air mixture hard to light, causing gas to build up. The tech can easily fix this.

Too little gas at the burners--Like too much air, not enough gas makes it hard for the gas-air mixture to ignite. This is can be caused by low gas supply pressure. The tech will have to examine what's causing this.

Dirty, restricted or weak pilot light--If you have an older furnace, this may be the problem. These pilot light issues prevent the main burners from igniting.

There are a ton of other causes (like misaligned or dirty burners), but you get the idea.

Why delayed ignitions are costly and dangerous

Several explosions by the delayed ignition can damage the furnace. It can also burn those trying to reignite the furnace pilot while extra gas is present (this is commonly called a "flash burn.")

This happens to more people than you'd think, like this woman from Denver who burned her face trying to relight her pilot light.

Delayed ignition can also result in the excess flames cracking the heat exchanger of the furnace (the most expensive part of the furnace) or allow the flames to roll out of the combustion chamber and result in a house fire.

Call a professional technician for help

Please don't try to solve this problem yourself. You could get hurt. Call a Lawton, OK heating company that knows their stuff.

Contact Pippin Brothers to repair your furnace if you feel you are experiencing this problem. Alternatively, a precision tune-up and professional cleaning of your furnace can uncover symptoms that lead to this hazardous problem and address it before it has catastrophic consequences.

Pippin Brothers is the Lawton-area's most trusted heating, air conditioning and plumbing company. We've been serving Oklahoma since 1978. Contact us for more information.