Advanced Air

Can I Run My AC Without a Filter for One Night?

October 25, 2017

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We get it—emergencies happen. One night you might remove and toss a dirty air filter only to realize that the stores are closed and you don’t have a replacement filter.

So is it really that bad to run an air conditioner without a filter for a short amount of time?

Here’s our professional answer: Running the AC without a filter just for one night won’t hurt your AC system, but it sure won’t help it either. Note: Running the AC any longer than a night without a filter risks serious damage and poor indoor air quality.

To help explain our answer, let’s first look at the role your air filter plays in the AC process.

Your air filter is there for 2 big reasons…

Your filter has 2 jobs:

  1. To purify your home’s air
  2. To keep your AC system free of dust and dirt

Think of your air filter as a bouncer: it stands guard 24/7, allowing clean air into your AC system/home but preventing harmful dust and contaminants from ever entering.

You see, air has to pass through your filter before it’s cooled and blown back into your home. And because your filter is composed of tightly woven material (fiberglass, paper or cloth), larger particles in the air like dust, pollen, mold spores, etc. get trapped in the filter.

Now that you know why your air filter is there in the first place, let’s look at what happens to your AC system when you don’t use one.

What happens when I run my AC without a filter?

The longer you run your AC without an air filter, the more contaminants get pulled into the AC system, eventually leading to poor indoor air quality and expensive AC problems.

Let us explain…

Problem #1: Lower indoor air quality

Without a filter there to trap air pollutants, your home’s air quality will deteriorate. That’s because the same air contaminants will just circulate through your home. 

But what’s worse is that you’re likely bringing even more pollutants into your home on a daily basis. Pets, guests, leaky air ducts and even vacuuming can add more and more pollutants to your home’s air.

Eventually, poor air quality can lead to:

  • Flu-like symptoms
  • Nose and throat irritation
  • Itchy, watery eyes
  • Increased chance of asthma attack
  • Respiratory disease

Problem #2: AC problems

The biggest problem with running the AC without a filter is the dust/dirt that settles inside the AC system, restricting airflow over your evaporator coils.

You see, your evaporator coils sit inside your AC air handler and are filled with cold refrigerant. This refrigerant is what actually cools the air. As air passes over the cold coils, heat and moisture is absorbed by the refrigerant.

diagram of the evaporator coil inside the AC system

Your evaporator coil, seen above, absorbs both heat and moisture from the warm air inside your home, turning it into the cool, conditioned air that you feel at your AC vents.

But if there’s insufficient airflow over those coils, they can’t absorb as much heat. And eventually, the (already cold) refrigerant drops so low in temperature that the coils freeze over.

Related: Why Is My Air Conditioner Frozen On the Inside?

a frozen evaporator coil

Frozen evaporator coils

3 AC problems caused by frozen evaporator coils:

  • Warm air from your AC vents
  • Higher-than-normal monthly energy bills
  • Compressor replacement (this can cost up to $2,375)

Need more filter tips? Ask a Florida tech

Need help replacing a clogged filter? Or want to upgrade your air filter to capture even more air pollutants?

We can help. Just contact us and we’ll send over a professional who can offer professional help and advice.

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