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HVAC Preventive Maintenance: Guide to HVAC Filters – Part I

Posted by CLS Admin on January 06, 2014


The word ‘filter’ shouldn’t leave much to the imagination. It’s truth in advertising. A filter…filters.

And that’s a good thing for everyone concerned. In the realm of HVAC, filters matter big-time. When they’re clean and working properly, they keep HVAC units running smoothly and efficiently, saving building owners and managers’ time and money. They also keep indoor environments clean from dust, mold, dirt and other contaminants.

On the other hand, dirty air filters cause HVAC units to work harder and consume more electricity. When an HVAC system works harder, it not only uses more energy, but it also breaks down more frequently.

In fact, according to the Houston Lighting and Power Company, “…a clogged air filter causes a 10% reduction in air flow and increases operating costs by 11%. Your air conditioner works harder to reach the thermostat setting, and you end up paying for energy that doesn’t cool anything.”

Folks at the Louisiana State Extension Service bolster that argument. “A slightly dirty filter can reduce the capacity of a typical 2.5-ton residential air conditioner system by ¼ ton. This illustrates how important air flow is to performance.” 

Air filters truly are essential to the smooth operation of HVAC equipment. They maximize energy efficiency, mitigate maintenance costs, and promote healthy and productive indoor environments.

When automatic heating equipment was first manufactured, air filters were installed to protect the equipment, not to clean the air for building occupants. This is because dirt that accumulates on a blower's "air foils" (blades) of a “squirrel cage” (wheel) dramatically reduces that blower’s output. 

With the advent of air conditioning, not only are filters important to keep the blower clean, but they also keep the evaporator coil clean. If your unit’s blower and/or coil become dirty, then air flow is reduced. Your equipment loses capacity as a result, and your utility bills rise. If the airflow is reduced enough, your evaporator will freeze the condensing water and completely block the airflow.

At least three things can happen at this point. None of them is good:

  1. The conditioned indoor space gets warm.
  2. You run the risk of liquid refrigerant seeping back to the compressor, which will reduce
    its lifespan. 
  3. The freezing of the coil can cause refrigerant leaks in the system.                 

But wait – there’s more. You’ll probably pay for a service call in the process, you’ll definitely pay higher utility bills, and you may likely face water damage when the block of ice melts. And of course, once that melting is complete, yet another additional service call will be needed to clean the blower and evaporator coil.

Following the energy crunch in the mid-1970s, consumers clamored for lower energy costs, while the Federal government echoed those sentiments by establishing tough efficiency mandates. HVAC manufacturers responded, and consequently, today’s HVAC equipment runs far more efficiently than its predecessors. Partly, this is due to manufacturers increasing the number of fins per inch within an HVAC unit, thus increasing the total radiation surface, which makes the coil more efficient.

But efficient design is only a foundation. Filters – and effective filter management – are crucial to the smooth, long-lasting operation of today’s HVAC units.

Air filter management is the most cost-effective maintenance tactic for HVAC equipment. And while it may seem obvious, we’ll state it nonetheless: Filter management means more than just changing filters. Rather, filter management begins with selecting the appropriate filter; it continues with strategically planning the frequency of maintenance; and it’s capped by selecting a reliable and experienced company to service your units. 

We’ll cover this topic in more detail in our next post. Until then, please call us at 800-548-3542 to learn more about CLS’s national HVAC services, or all other CLS services.


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