Aluminum Coils and Air Filters

Some of you have had to replace your air conditioner’s or heat pump’s cooling coil in the past few years. If your new coil is constructed of aluminum there are some changes you may be interested in. The changes are for the better in the long term but there are things you should know that will be reviewed here.

When, in the interest of efficiency, home air infiltration was reduced starting in the 1970’s the air inside of homes became more contaminated because the air was not exchanged as often. Some of this was noticeable to the occupants but other events were observed by your air conditioning technician.

Technicians started to notice that copper indoor cooling coils leaked refrigerant after 5 to 8 years of use compared to 20 or more years previously. One cause among others was the increased concentration of chemical compounds of chlorine and sulphur in household air. These compounds react with the copper tubing used to manufacture cooling coils.

A ForeFront Air Handlers Coil beauty color

American Standard ForeFront Air Handler All-Aluminum Coil

Some manufacturers switched materials and now construct their coolings coils with aluminum tubing which is not affected by these chemical compounds. One benefit we in the industry have seen is a large reduction in refrigerant losses because of leaks. These aluminum coils are actually reducing by a large factor the amount of ozone depleting chemicals released into the atmosphere. A larger benefit to the homeowner is the extended life of the outdoor unit. Running an air conditioner with an insufficient refrigerant charge shortens the life of the compressor.

But there’s always a ‘but’. Copper coils were performing a function I was unaware of. Copper is toxic to mold and it was treating the drain piping, after a fashion, with copper sulfate and reducing drain problems.

American Standard® started using aluminum in about 2005 and we have noticed a slow increase in the frequency of drain problems and, to the observant technician, a change in the color of the mold clogging the drains.


Light colored mold on the ground flushed from an aluminum coil

Aluminum is not toxic to mold so it provides none of the treatment that copper coils performed in the past.


Mold has three necessary conditions to propagation:

  1. Darkness or absence of ultra-violet light
  2. Water or damp air greater than 60% relative humidity
  3. Food

As conditions 1 & 2 exist in all air conditioning equipment, to break the chain of mold propagation we can eliminate # 3 – depriving it of a source of food.

Household dust is comprised of hair, fibers, skin cells and other small particles. Visible particles such as hair and fibers are easily caught with most air filters. But smaller particles require improved filters to remove them from the air stream and the cooling coil.

Fiberglass Air Filter

Fiberglass air filter

Don’t consider using this filter on an air conditioner. Small particles fly through it easily. This filter is ineffective in the control of mold.


Pleated media filter

Pleated media filters are better as they catch the smaller particles like skin cells; but they restrict the flow of air and reduce the efficiency of the air conditioner. Also in variable speed indoor units, that restriction causes the ‘smart’ blowers to speed up to overcome the restriction and increase electricity consumption.

Return Grille Filter

In-wall 5″ thick media filter


Cartridge media filter

There is now available an easy solution that requires little to no installation costs. Five inch thick pleated media filters that usually fit in your wall return air grille. These filters can be ordered online directly from the vendor. The source we have been using can be found here. Make certain you measure your existing wall grille before ordering. This is such a good option that we recommend replacing your wall grille to match the available filters if you find that necessary. We can replace the wall grille for you.

If your return duct system is leakproof and you are diligent with air filter replacement you can eliminate drain problems with your air conditioner.

About Swinson AC Co

Residential Air Conditioning and Heating Contractor in Central Baldwin County Alabama and the Eastern Shore 964-9009 990-0998
This entry was posted in Air Conditioning, Allergies, Condensate Drain, Dirty Sock Syndrome, Mold, Odors, Technology. Bookmark the permalink.

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