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.

Posted in Air Conditioning, Allergies, Condensate Drain, Dirty Sock Syndrome, Mold, Odors, Technology | Leave a comment

Fireplaces and your central heating system


Fireplaces offer a cozy view and a warm, radiant heat to enjoy in your home. But, if your primary source of heat is from a central heating system, a fireplace can waste the fuel it consumes along with the fuel used by the central system. It will also make the farthest places in your home colder. 

Fireplaces can be fueled by wood or natural gas. One pound of fuel requires 15 pounds of air for combustion. Unless your fireplace has an outside air source, this air comes from your already heated home air. In addition to combustion air, the heated flue pulls in another 15-20 pounds of air from the house to the outside.

00-tiling-fireplace-1208-xOpen fireplaces are a primitive method of home heating.


Glass Fronts can reduce the amount of air drawn from the home.


Wood heaters


regency-wood-insertFireplace Inserts

that contain a heat exchanger capture the heat that otherwise would go up the chimney with the smoke. They can provide heat to the home along with a central heating system.

If your primary heating system is a central gas, electric or heat pump system, the system should be turned off during operation of an open or glass-fronted fireplace. Wood Heaters and Fireplace inserts, on the other hand, can be operated together with a central system. In this part of the country they can produce much more heat than necessary to heat a home and are operated in a throttled condition. A variable speed fan on your central system can be used to distribute this heat to the rest of the home without causing a drafty feeling.

Prefabricated fireplaces now outnumber masonry fireplaces. They are much less expensive to build. I see very few of these with a heat exchanger like you would find on a fireplace insert, but that type does exist. The majority of these use gas logs with a triple-wall flue to the outside and have the efficiency drawbacks of masonry fireplaces as described above. There is a way to use these for home heating in an efficient manner: Vent-Free Gas Logs.


Vent-Free Gas Logs come with an Oxygen Depletion Detection System and do not produce dangerous carbon monoxide. They can be operated with a closed flue or without a flue. This makes them nearly 100% efficient in operation. They do present drawbacks compared to a central system; all products of combustion are dumped into the living space.

The products of combustion are:

  • trace amounts of hydrogen sulfide
  • large amounts of water vapor
  • Carbon Dioxide

Hydrogen sulfide is not noticeable to humans in trace quantities but it is a corrosive gas. Large levels of water vapor raise the relative humidity in the home and can cause sweating of glass and window sashes. Carbon Dioxide is non-toxic to humans but elevated concentrations can make you drowsy. This is controlled for with the Oxygen Depletion Sensor that is part of a vent-free gas logs device.

I’ll include a note here about Carbon Monoxide. Carbon Monoxide is toxic and accumulates in the blood. It is created through the incomplete combustion of hydrocarbon fuels. High accumulation in the blood can be fatal. The symptoms are similar to influenza. If you have propane or natural gas supplied to your home you should own one or more carbon monoxide detectors. They are incredibly cheap and very reliable.

Gas logs are a much cheaper way to achieve high efficiency gas heating. A comparable 96% AFUE efficient Gas Furnace can cost as much as $5,000 or more. But of course there is a trade off – Gas logs degrade the quality of air inside the home.

I remember going to an elderly aunt’s home in Mobile in the 1960s who heated her home with free-standing radiant gas heaters. The indoor environment was oppressive because of the elevated humidity and odor of combustion products. I didn’t, of course, know these causes at the time but the indoor air was unpleasant nonetheless.

New furnaces draw combustion air from outside the home, recover almost all heat from the fuel and then dump the products of combustion outside. All this without adding or removing anything from the air inside the home. Gas logs are used primarily to heat the room with the logs and to also enhance the ambiance. As nice and quiet as our furnaces are, they’re not much to curl up in front of.

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IAQ – Allergies and Asthma – Odors in your home

A visitor to your home will sense them more quickly than you. Prolonged exposure makes them invisible to you. You will often notice them when you first arrive home. Odors are part your body’s self-defense warning system.

Dogs, cats, hamsters, carpet, cooking, people all give off cells, hair, fur, gasses, VOC’s that are detectable to the human nose. To some people it’s just a smell. To some it can trigger an allergic, histamine reaction. I’m not an expert in allergies but my work involves dealing with the conditions related to humidity and air filtration. Controlling relative humidity in South Alabama is a larger part of maintaining comfort than in most other non-coastal locales. Mold grows in humid conditions so that makes air conditioning technicians a resource for controlling airborne mold inside the home. We apply and repair the equipment that controls humidity, and filters particulates from the air.

Newer houses are constructed to leak less air than older houses. This trend started earlier in the North as heating homes uses quite a bit of fuel. Energy efficiency in air conditioned homes moved this practice to the southern United States in the 1970’s. I mention this to point out that you live in a different structure from your parents. The home you grew up in during the 1950’s, 60’s, 70’s and 80’s exchanged air more freely with the outside which reduced the concentration of various pathogens and chemicals. Tightening up homes creates a different indoor environment but ventilation practices have not kept pace with these changes.

Ventilation – Kitchen range hoods carry steam and aerosol oils from cooking directly to the outside. The best way to keep cooling odors reduced is the kitchen range hood. Open the cabinet above your range. If there is no duct visible you probably don’t have a vented range.

Use bath exhaust fans after showering until the mirrors clear and then 15 minutes longer. Consider removing the inexpensive fan that came with your home and replacing it with a larger model. Quiet models with heaters for winter use save energy by heating the bath while you are damp from bathing. Removing excess humidity reduces the moisture necessary for mold spore propagation.

Air Filters – There are several options available here. Even the least expensive is effective if they are changed regularly. panel-air-filter-392070How often depends on your home: More often in summer, less often in winter. Looking at them is a good indicator of the correct interval.

Extended surface filters are a good option but are not always commonly available. air-cleaner-filtersThe advantage is that they offer less resistance to airflow while still filtering a very small particle. People that use them properly gain the advantage of clean equipment and extended life. The dirt that collects on the cooling coil accelerates corrosion that leads to refrigerant leaks and the moldy odor noticed when the air conditioner comes on. Customers sensitive to that odor usually call us asking to have the ductwork cleaned. Here is a photo from a few weeks ago.

Dirty indoor Cooling Coil

Dirty indoor Cooling Coil

Click on the image and you can see at the bottom where I cleaned a small section with a wire brush. The rest of that is mold living on the coil. It is more common to see this than not. Once mold gets started, it maintains itself very easily and is difficult for you to remove.

Carpet – Carpet can be cleaned. The pad under a carpet cannot be cleaned. Dirt from outside sifts through the carpet and pad and forms a silt-like layer on the underlaying floor. If you watch carpet being replaced, look at the fine powder on the floor under the pad. 3 month air filters last 3 months in a carpeted home, 6 weeks or less with wood or tile (2 to 4 weeks with pets). Air filters last longer in a carpeted house because carpet catches a large amount of dirt. Carpet in a home collects years worth of debris from shoes, skin cells from humans, spills, dust mites.

The dirt under the pad can have dust mites which can trigger allergies. It also has bacteria in abundance; not ‘can have’ but ‘has’. Interior relative humidity above 65% provides an ideal environment for mold. Mold propagates well in dark, damp places and bacteria is a food-source for mold.

A normally functioning central air conditioner will maintain right about 55% relative humidity (rh) many months of the year .  In the spring and fall during mild weather you will see 60 to 80% rh for extended periods.

If you are having allergic reactions and you have carpet, consider hard-surface flooring as an alternative.

Dirty sock syndrome – This condition mostly affects heat pump indoor units. The aluminum fin of the indoor coil becomes etched chemically in a short time of operation forming microscopic fissures in the surface of the fin. A cooling coil in a typical home has up to 300 square feet of aluminum fin surface. Mold growing on these 300 square feet gives off a moldy, dirty sock odor at the first start-up in the winter. The wet mold in the fissure is heated by the heat pump operation and gives off a very strong repugnant odor for a day or so until the heat kills it. In the fall we routinely switch between cool and heat which generates a new crop of mold and odor.

Containment – Laundry hampers, compost pails and closed garbage cans can prevent odors from building up in your home. Damp clothes, food scraps and household garbage emit products of decomposition that linger and accumulate in textiles in your home. Containing them reduces the odors.

Pets – Control of pet odors varies with the pet. In my life I have had hamsters, rats, birds, cats, dogs, iguanas and probably some that I forget. I won’t go into the varied types of odors and requirements of keeping down pet odors. Litter boxes, cages, and the pets themselves all require different measures. Assuming that each pet is cared for and their quarters are clean, there are still odors that can be readily detected by visitors. For this there is a magic bullet(s). Oxidizers. That annoying guy on the Oxiclean commercials is selling a product that uses this principle in cleaning fabrics. It can also be used to clean air.

There are devices available that generate oxidizers, mainly ozone and hydrogen peroxide. These are molecules that are dispersed into the living space from devices inside the return or supply duct. These devices consume less than 25 watts of electricity to power ultra-violet lamps.

Ozone and hydrogen peroxide react with mold and viruses in the ductwork and in the household environment killing them and/or stopping their propagation. Ozone (O³) is generated with a less expensive device than hydrogen peroxide (H²O²). Peroxides have a less noticeable odor than ozone. Also, there are limits to the amount of ozone you want in your home as it can irritate lung tissue. Peroxide generators are surprising in their effectiveness in eliminating odors inside the home. Installed cost of a peroxide generator is about $750.00 and they require an element replacement every 3 years at a cost of about $350.00. This gives an annualized cost of operation over a 15 year period of $165 per year or 44¢ per day. It is a luxury but it is a nice luxury. It can really make your home smell fresh with no masking odor. Also there is a reduction in allergens which can reduce histamine reactions. We have an ongoing offer on these as they are not cheap and it is difficult to get consumers to assess their value. Here is the offer: We will install a REME Generator in your home for $750.00 and let you try it for one month. If you don’t think it helps you enjoy your home, we will take it out, repair the ductwork entry point and write you a check for $650.00. We do this to weed out people that would abuse the offer. I think they are worth it and want to let you evaluate it at a small risk.

Other points in your home to review are mainly structural in nature. Some structural issues are air conditioning related because of the temperature of the building materials and the humidity of the outside air. I will go other some of these items in future articles.

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IAQ – Allergies and asthma – Ductwork

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IAQ – Allergies and asthma – Indoor AC Equipment

Indoor Air Quality

In the previous article on Indoor Air Quality, the section of your air conditioning system from the wall filter to the indoor equipment was covered. This installment covers the indoor machinery. Two types of equipment are used depending on the fuel used for heating. If you have a gas furnace your indoor cooling coil is less accessible than if you have a heat pump.

Dirty Indoor Cooling Coil

Dirty indoor Cooling Coil

Above is a view of the inlet to a cooling coil (click for enlarged view). All air that moves through the cooling system passes thru this coil which is wet and functions as a very efficient air filter. The coil remains wet during cooling operations and collects nearly all dirt and debris that is not filtered upstream. This coil is very difficult and expensive to clean and that is one reason why timely filter replacement is so important. Look at the lower center section to see an area that we cleaned with a wire brush. This coil is over 2 inches thick; a wire brush cleans the first .125 inch so it only clears debris from the surface.

Dirty Blower Wheel

Dirty Blower Wheel

This isn’t a great photo but it shows typical growth of mold on a blower wheel. The blower is after (downstream of) the cooling coil. You would think that air would be dry after leaving the coil but it leaves the cooling coil at 100% relative humidity. The air going through the blower deposits dirt on the blades reducing their effectiveness. Also, the blower section is dark and wet so the bacteria in the dirt furnish everything necessary for a mold colony (shown as round globs in the photo).

There is very little a homeowner can do to clean this equipment. Before the introduction of the American Standard ForeFront® Air Handler, air handlers weren’t designed to be cleaned, even by professionals; cleaning was a difficult, improvised process.  Proper filter replacement schedules mean that the interval between air handler cleanings can be 10 years or more.

The next installment will deal with mold in ductwork and duct cleaning, one of the most frequently asked questions we receive.

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IAQ – Allergies and asthma – Return Air Duct

SneezeIndoor Air Quality

Allergies and asthma are triggered by the body’s reaction to substances in the environment. Sometimes the cause is:

  • known from experience
  • told to you by your physician
  • unknown

I am starting a series of short articles on these problems and how they relate to air conditioning. This guide will allow you to investigate it yourself or to look over the shoulder of a technician. There are many deceptive practices in the field of mold remediation; some of it is just overkill on a problem; some is dishonest; some is inattention to the problem. As in all issues of your health, it is up to you to keep plugging away and asking questions until you find your answer.Heater Closet - 1

Our interest here is to ascertain how well the system is sealed from the outside air and that air’s entrained moisture and contaminants. The first place to look is the largest air grille in the system, the return air grille. Starting at the return grille to the supply grille where the conditioned air enters the home, all surfaces inside the air conditioning system are shielded from view and cannot be cleaned by the homeowner. The purpose of these articles is to explain what goes on in these spaces.

At this location you should see an air filter. Many homes have the filter in the furnace or air handler and not here at the return air grille. Having a filter at locations other than the return air grille is universally sub-standard. Not having a filter at the starting point of the system causes heavy accumulation of household dust under the furnace and in the return air plenum or return air duct.

Open this grille and use a flashlight to look around the space.

1. If the furnace is in the closet above you –
The only holes should be the ones for the filter and at the bottom of the furnace; the rest of the space should be ‘bubble-tight’. This is very important. When the filter is in place, the plenum is at a negative pressure and will pull air in through every crevice. As the filter loads with dirt, this negative pressure increases. This intruding air is unfiltered, humid and from the attic.

If there are holes, the repair for this does not require high skills; it is pretty tough getting in and out of the hole amongst the piping nonetheless.

The preferred material is 1/2″ thick sheetrock but that is during construction. After the fact, we use 1/2″ styrofoam exterior building sheathing and expanding foam. We are attempting to build a smooth, sealed, cleanable enclosure between the return air grille and the furnace.

2. If the furnace is under the house or in the attic –
Most homeowners are out of their depth at this point. This space behind the return grille is an extended duct to the furnace. Reliable repairs to duct material require developed skills and only the handiest of homeowners should make these repairs. As with the closet mounted furnace, this section is at a negative pressure and pulls in outside air if defective. Here is a good tip for anyone with a furnace in the attic. If you are spry enough to walk the ceiling joists of an attic or it is decked, look at the point where the return duct rises through the ceiling to the attic. There will be insulation covering this location. If the insulation is dirty in a ring 4-6 inches away from the duct, you have found an important duct leak. The negative pressure from the duct is pulling air through the insulation. The insulation filters dirt from the air and becomes darkened with age.

Modern air conditioning works best when it doesn’t have to process new air. It recycles the same air through the system removing moisture and heat and contaminants. In a normal house, clothes dryers, range hoods, bath fans and door traffic supply plenty of fresh air.

If you are going to win the battle with mold you have to deny it the things it needs to live:

  1. moisture
  2. darkness
  3. food

If you live near me, your summer consists of 8 months of 90% or higher relative humidity. Mold cannot grow in an environment of 55% relative humidity or less. When we replace indoor air conditioning equipment, we always improve the seal; very often we find huge holes that have been pulling attic air into the house, sometimes for decades.

If you will follow the things I post on here in the coming weeks you can educate yourself about mold allergies related to duct systems. This treatment of the return duct is just the start of the process but I will take others in turn. Some houses are easier to correct than others but the causes of mold allergies are known causes. There is no reason for you to suffer in your home from allergies caused by your home.

Posted in Air Conditioning, Allergies, Asthma, Ductwork, Mold, Odors | Tagged , , , , | 1 Comment

Good news about freon leaks

In preparing our annual refrigerant purchase in light of the upcoming refrigerant phase-out I made a surprising discovery.

Refrigerant usage analysis

Click on the link above and you will see the result of American Standard’s all-aluminum coils sold by Swinson Air Conditioning.

Our fiscal year starts on Oct 1 so the year 1998 is truncated. What the chart indicates is the more than halving of R22 refrigerant sales in a record overall year for Swinson Air Conditioning. American Standard changed production of indoor cooling coils for gas furnaces in 2004 and heat pump air handlers in 2010 to all-aluminum manufacturing.

We started to emphatically recommend to our customers that they not repair their copper coil indoor equipment but to let us replace it with all-aluminum machinery. It has taken some time to get traction but last year’s sales of R22 is down more than 50% by weight over the previous year.

We place a special emphasis on locating and repairing refrigerant leaks because we see the year to year expense that the repairs can stop. This drop in sales represents large savings for our customers as well as a reduction in the release of refrigerant gas to the atmosphere. And the savings extend into the future at no additional cost to our customers.

This illustrates our commitment to do our part in giving you a comfortable, healthy home at the lowest expense.

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