Understanding the Danger of Furnace Flame Rollout and How to Prevent It
Gas furnaces are designed so that they operate safely and mitigate against any potential hazards. Nonetheless, there are various issues that have the potential to create a safety hazard, and the chances of this happening are higher the older the furnace gets or if you neglect any of the important yearly maintenance tasks. One of the biggest potential hazards is a furnace flame rollout, and today we’re going to take you through exactly what a flame rollout is, why it can happen, and what steps you can take to prevent this potentially dangerous hazard.
What Is a Furnace Flame Rollout?
When a furnace is working correctly, all of the flames created when the unit burns gas remain safely trapped inside its combustion chamber. The combustion chamber is connected to the heat exchanger, which is essentially a series of metal pipes that run from the combustion chamber to the exhaust flue.
When gas is burned inside the combustion chamber, it produces hot fumes that flow out of the chamber into the heat exchanger. This process causes the heat exchanger to become almost glowing hot. The HVAC blower fan works to circulate cold air over the heat exchanger, and the heat is then transferred from the exchanger into the air.
Although the hot combustion fumes flow out of the combustion chamber into the heat exchanger, the system is designed to keep all of the flames inside the chamber. A flame rollout occurs when there is some issue that prevents enough oxygen from getting inside the chamber. If the flames are starved of oxygen, they will quickly start to grow much bigger in an attempt to capture oxygen. This can result in the flames escaping or “rolling out” of the combustion chamber, hence the term flame rollout.
It is usually fairly easy to tell if your furnace has suffered a flame rollout. In most cases, you will see that noticeable discoloration or singing on the furnace and its components. You may also even see the flames shooting out of the chamber if you look at it while a flame rollout is occurring.
What Issues Can Cause a Furnace Flame Rollout?
The combustion fumes produced by burning gas are no longer flammable. A flame rollout occurs because these inflammable fumes get trapped inside the combustion chamber, which can happen for a few different reasons. As the fumes build up inside the chamber, they will eventually start to starve the flames of oxygen and eventually lead to a rollout. This can cause serious damage to the furnace as the flames can reach parts of the unit that are not designed to withstand high temperatures. A flame rollout can also heat the entire furnace and surrounding area to the point where it creates a serious fire risk.
Flame rollouts usually happen for one of three reasons. One possible cause is that the outlets between the combustion chamber and the heat exchanger have become clogged with grime and soot. This will prevent much of the combustion fumes from flowing out into the heat exchanger and cause them to build up inside the chamber. This issue can easily be avoided by having your furnace professionally maintained every year as the technician will clean the entire furnace and make sure the heat exchanger isn’t clogged or obstructed.
Flame rollouts can also occur because the exhaust flue is clogged. This can happen because leaves and debris get stuck inside the pipe where it exits the building or because animals have decided to nest inside the pipe. The same issue can also occur if the flue is damaged, poorly designed, or not installed properly. Any of these issues can prevent the combustion fumes from being dispersed through the flue properly, causing them to accumulate inside the combustion chamber and leading to a flame rollout.
The most serious issue that can lead to a flame rollout is a cracked heat exchanger. Whenever the furnace is heating, the hot fumes cause the metal exchanger to slightly expand due to the high heat. The exchanger then contracts again as it cools. Over time, this can weaken the metal and eventually cause the heat exchanger to crack simply as a result of wear and tear due to aging. That being said, the most common reason a heat exchanger cracks is due to extreme temperatures caused by the furnace overheating.
A cracked heat exchanger can make it more difficult for the combustion fumes to be drawn out of the combustion chamber and thus lead to a flame rollout. Still, the bigger issue here is that a cracked heat exchanger will also allow some of the fumes to escape into the ductwork, and this can cause carbon monoxide to circulate throughout the entire building whenever your heating system is running.
If you suspect that your furnace is having flame rollout issues, the technicians at North Point Air Conditioning & Heating can inspect the unit and determine what is causing the problem and how to fix it. We work on all brands and types of furnaces, and our team also installs and services air conditioners, ductless mini-splits, thermostats, and indoor air quality equipment. If you need a furnace inspection or any residential or commercial HVAC service in Spring or the surrounding areas, give us a call today.