3 Airflow Issues That Reduce Your Gas Furnace's Efficiency

Posted on: 22 December 2014

You expect your gas furnace to keep your home warm every winter. However, since you haven't taken time to properly maintain your furnace over the past few years, it just doesn't seem to operate as efficiently as it once did. As a result, you have to leave your furnace active for hours at a time before your home becomes warm and comfortable—which is a sure sign of an airflow problem. Instead of continuing to use your inefficient furnace, inspect it for these problems and perform or arrange for the necessary repairs.

Why Does Airflow Matter So Much?

Forced-air furnaces must receive a high volume of air to produce heat. Without sufficient airflow, your burner assembly won't completely ignite the gas supplied to your furnace. Additionally, the heat produced by your furnace won't ventilate throughout your air ducts and into the various rooms of your home as efficiently as possible if there's an airflow restriction throughout your HVAC system.

Restrictive Air Filter

All airflow throughout your furnace must first pass through your air filter. As air flows through your filter, airborne debris, such as dust, dirt, and pet fur, becomes trapped in the filter—which prevents the debris from being ignited inside your furnace.

However, when enough debris collects inside your filter, the pores of your filter will become clogged. As a result, the amount of air that can flow through your filter at any given point will be reduced. Eventually, your filter can become so clogged it allows components inside your furnace's combustion chamber to overheat and sustain damage.

Luckily, you can replace your filter in only a matter of minutes. To do so, shut off the power and gas to your furnace and open your blower compartment's access door. Pull your dirty filter out from the side of your compartment connected to your return duct. Wipe away any debris around the filter's location before sliding in a compatible replacement filter.

Once you replace your filter, inspect it every month to determine whether or not it needs to be replaced again. By regularly inspecting and replacing your filter, you can ensure that it doesn't become clogged once again.

Improperly Sized Ducts

The air ducts throughout your home must be sized according to the efficiency of your furnace and the power of your blower motor. If you replaced your furnace without replacing your existing air ducts, then your furnace has likely underperformed since day one. To fix this problem, an HVAC technician will have to measure your air ducts and compare the sizes with your furnace's specifications. If your technician finds that your ducts are improperly sized, they'll need to be replaced.

Air ducts sized too large for your furnace will reduce the speed of the air flowing throughout your HVAC system. As a result, it will take a long time for air from your furnace to ventilate into your home. Air ducts that are too small for your furnace will make it difficult for your blower motor to pull air into your combustion chamber—which prevents your burner assembly from efficiently igniting the gas supply delivered to your furnace.

Dirty Fan Wheel

Your furnace's blower motor is a centrifugal fan. A centrifugal fan works by spinning a fan wheel (also referred to as a squirrel cage). As the wheel spins, it's blades pull air into your blower and towards your combustion chamber.

However, as minute amounts of airborne debris slip through your filter (as well as through unsealed areas of your blower compartment), your fan wheel's blades will become dirty. When enough debris accumulates on the fan wheel, the amount of air that can pass through the blades and into your blower will be reduced.

Cleaning your fan wheel is a difficult task that requires in-depth knowledge of electrical wiring and your furnace's design. For this reason, it's best to leave the task of cleaning your fan wheel to a professional HVAC technician, like one from Aggressive Mechanical Contractors.

If any of these three problems are present in your furnace, then perform or arrange for the necessary repairs before the winter chill begins to turn your home into an ice box.