Photograph of a filthy air conditioning air handler filter Dirty Air Filters on Heating and Air Conditioning Systems

  • DIRTY AIR FILTER PROBLEMS - CONTENTS: Causes and effects of clogged heating or air conditioning air filters - what problems are caused by a dirty or clogged air conditioner or furnace filter? Not just weaker airflow.
    • WASHABLE AIR FILTERS how to clean & inspect a washable air filter used in a window unit, split system air conditioner, or portable air conditioner
  • POST a QUESTION or READ FAQs about clogged HVAC duct air filters, causes, effects, cure and prevention - washable air filters
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Clogged or dirty air conditioner or furnace filter troubleshooting: This article explains the causes and effects of clogged air conditioning or heating air filters.

Air filter clogging may be the result of high indoor debris levels, abnormal condensate handling or indoor moisture, or even more subtle problems that need to be corrected.

A clogged HVAC air filter increases heating and air conditioning operating cost and in some cases can even be quite dangerous. We describe how to recognize a dirt-clogged air filter, and how to recognize replaceable air filters versus washable air filters.

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Dirty Air Conditioner Filters Cause Multiple Problems for an Air Conditioning System

Photograph of a dirty air conditioning filter

Dirty Air Filters: are a source of increased operating costs and poor cooling system operation. Dirty air filters can and in fact probably will have these bad effects:

  1. reduce air flow into the building

  2. increase the operating cost of the heating or air conditioning system
  3. cause dirt to accumulate on the fan blades, wasting your energy dollars -
  4. cause excessive dirt build-up inside the duct system, leading to mold or allergen problems in a building and to the need for more costly duct cleaning or replacement
  5. block the cooling coil itself with dirt, reducing system effectiveness and possibly leading to costly repairs
  6. lead to frost build-up on the cooling coil and reduced or totally blocked air flow in the system
  7. eventually permit dirt to bypass the filter where it soils and blocks the blower fan itself, leading to more costly repairs.
  8. and in extreme cases a clogged HVAC air filter can be dangerous: a blocked air filter can be "sucked" out of position and right into the blower assembly. If this happens the flower fan can jam, overheat, and the result is a risk of actual fire in the equipment. See HEAT RECOVERY VENTILATOR FIRE for an example.

Dirty HVAC air filter (C) Daniel FriedmanThe filters on an air conditioning or hot air heating system should be changed monthly when the system is in use. Discuss with your heating/cooling service professional the possible need to clean the blower fan and duct work.

Air Filter Accessibility

An air filter that is installed where it is not readily accessible may in fact be ignored completely by building owners/occupants, and may rarely if ever be serviced.

Be sure to inspect your HVAC system and ductwork thoroughly to be sure that you know where any and all air filters are located.

A forgotten air filter will mean poor heating or cooling in the building and higher energy costs.




Washable HVAC Air Filters: Washing a Split System Air Conditioner Plastic or Nylon Air Filter

Wall-mounted split system air conditioners as well as window air conditioner units include one or more removable air filters that are designed to be simply rinsed clean using cold water.

Inserting a cleaned washable air filter into the air conditioner unit (C) Daniel FriedmanAt left you can see the author replacing the left-hand air filter of a wall-mounted split system air conditioner after having washed it clean.

You can wash these plastic mesh filters in the kitchen sink using a dish sprayer but I prefer to perform the operation outdoors (shown below). Outside avoids messing up the kitchen and eliminates any risk of drain clogs.

Watch out: We have read of washable air filters that can be sent through your dishwasher.

We do not recommend this step - as you risk clogging the dishwasher or its pump with dust and debris that wash off of the air filter.

Details of how to remove, clean, and replace these washable air filters are found at SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS


Continue reading at ENERGY SAVINGS by AIR FILTERS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


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