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Air Duct Cleaning: How to Handle Air Handlers

Posted by Peter Haugen on Fri, Nov 04, 2016 @ 09:52 AM

McQuay air handler in mechanical room.jpg   McQuay rooftop.jpg 

Air Handlers are the heart of any HVAC system. They move the air (with a fan) and may also clean (filter) the air and condition (heat, cool, humidify) the air.  Air Handlers come in all shapes and sizes from the furnace in your home to a 40’ long commercial rooftop unit to a 5-15 ton packaged rooftop units you see on the roofs of most strip malls and office parks. 

Surface Cleaning Options:

An air handler can contain some or all of the following components: fan, motor, coils (heating or cooling or both), condensate/drain pan, and filters, fresh air intakes, mixing boxes.   You can’t clean all of these components the same way so let’s look at your cleaning options:

  • Contact vacuuming is probably the most popular air handler cleaning tool. You can contact vacuum all of the internal surfaces (sheet metal and insulation if it’s in good shape), fans, motors, walls, ceiling/floor, coils, drain pans etc.
  • Air washing with high pressure air can be used if you have the air handler under negative pressure (to control and collect the dirt/debris) from your vacuum collection system.
  • Pressure washer can be used on large air handlers without internal insulation where you can control the water flow. You must protect the motor and other electrical components however.
  • In many cases you will use several of these cleaning methods on one air handler. The desired end result however it so remove the accumulated dirt and debris from all the air stream surfaces.

Coil Cleaning

Coil cleaning improves the heat transfer capability of the coil which will lower energy cost and improve comfort. There are two types of coil cleaning:

  • Type 1 (dry cleaning of loose dust and debris on the coil surface)
  • Type 2 (wet cleaning of adhered debris on coil, drain pan and drain line surfaces).
  • A visual inspection will help you to determine which type of coil cleaning is needed. If the inspection reveals microbial contamination then you should use Type 1 and then Type 2 cleaning. If the inspection reveals fins that are damaged, deteriorating or showing signs of corrosion replacement may be necessary.

Type 1 coil cleaning (dry cleaning of loose dust and debris on the coil surface) may include a variety of methods to thoroughly remove accumulated debris including:

  • Contact vacuuming with HEPA filtered vacuum.
  • Brushes for penetrating between coil fins.
  • Using compressed air to blow out accumulated debris.
  • Using fin straightening tools.
  • If debris is still present after Type 1 cleaning then Type 2 cleaning shall be done.  

Type 2 coil cleaning (wet cleaning of adhered debris on coil, drain pan and drain line surfaces) shall be done only after Type 1 cleaning has been completed and may include:

  • Application of coil cleaner (in accordance with manufacturer ’s instructions). It is recommended that coil cleaning solution that is close to PH neutral be used.
  • Water washing at normal water line pressure.
  • Pressure washing equipment.
  • Hot water or steam cleaning equipment.
  • Condensate drain pan and line shall be cleaned and flushed.
  • Precautions shall be taken to capture rinse water when cleaning coils without a drain pain.
  • When cleaning electric resistance coils the power source shall be de-energized and locked out/tagged out. If wet cleaning, the coil should be thoroughly rinsed and dried prior to being re-energized.
  • If debris cannot be removed using Type 2 cleaning methods, replacement may be necessary. Visual observation of the coil surface can be misleading; therefore it is recommended that a static pressure drop measurement be obtained before and after cleaning to demonstrate the effectiveness of coil cleaning.    

Dealing with Fiberglass

Many air handlers have internal fiberglass insulation. You need to take a good look at the insulation to determine if the insulation is in good enough condition to withstand the rigor of cleaning. If the insulation is not in a cleanable condition then it must be removed. Depending on the condition of the insulation you have the following options:  

If the insulation is in good condition (cleanable)

  • You can contact vacuum it.
  • You can contact vacuum it and then apply an insulation repair coating. This is an economical way to improve the insulation surface and extend the life of the air handler. The coating locks down any remaining loose fibers, gives you a more durable air stream surface that is more resistant to air erosion and water, locks in and isolates any mold spores and smoke particulate remaining after cleaning, and is easier to clean in the future.

If the insulation is damaged, deteriorated (not cleanable)

  • Remove the insulation and clean the air handler.  You lose the acoustical and thermal benefits of the insulation plus it’s very hard to get all the fiberglass fibers out of the glue used to hold the insulation in place.
  • Remove the insulation and apply a coating over the cleaned surface to lock down any remaining fibers.
  • Remove the insulation and replace it with new insulation. Over time the new insulation will degrade just like the insulation you just removed unless a coating has been applied.
  • Remove insulation and replace with close cell liner. Closed cell liner is a good long lasting solution.

Drain Pans

Drain pans can be the most challenging surface in an air handler to clean and restore. Constant exposure to moisture can cause corrosion.  Severe corrosion will lead to leaks.   Preventative maintenance and restoration of a drain pan cost significantly less (in both time and money) than drain pan replacement. There are several products on the market designed specifically for drain pan refurbishment (Pancrete, Panseal, Safe Encasement, etc).  Only submersion or immersion rated coatings should be used. 

  • Cleaning via power washing, scrapping, wire brushing is typically required prior to coating.
  • Some coatings require the mixing of two different components together.
  • Some coatings require a submersible primer to be totally dry/cured before the submersible top coat is applied.
  • Most of these coatings can be applied with a brush, roller or spray equipment. When done properly these drain pan coatings deliver a refurbished drain pan that looks good and will last for years.


Air handlers come in all shapes and sizes and you need to be able to clean and refurbish them as needed. You have several cleaning methods to choose from and several options to clean and refurbish deal coils, fiberglass insulation and drain pans. 

If you have any questions about this blog article, contact Peter Haugen, ASCS, CVI at 855-Vac-Systems, 952-808-1619 or phaugen@vacsysint.com. Click on the following links for additional information on Coating HVAC Systems and Closed Cell Insulation


Tags: cleaning air handlers