Q-My air conditioning system didn’t work when I turned it on for the first time this season. After spending $60 on a service call, I learned that a huge block of ice had formed inside my furnace. The service woman said the coil was dirty.
That doesn’t make sense. It seems to me the air would be much cooler if it was blowing over a block of ice. What happened? Can it be prevented in the future?
A-Once that ice melted and the coil was cleaned, I’ll bet the system worked fine. You possibly caused the problem by not changing your furnace’s air filter on a regular basis.
Your furnace contains an evaporator coil with many small fins, through which the furnace blower circulates air. The air conditioning effect comes as the coils’ continuous tube of refrigerant chills the fins.
When you turn your air conditioner on, the main blower in your furnace begins to recirculate the air through your house. As humid air passes over the cold fins of the coil, the water in the air condenses on the fins, just like on a cold glass of iced tea on your patio table. Everything works fine if enough of this warm moist air can move fast enough over the fins. If not, the temperature of the fins can drop below 32 degrees Fahrenheit. Ice then starts to form on the fins and soon the coil is a solid block of ice.
In your case, the air passageways between the fins became blocked by dirt and the dirt slowed down the air flow through the coil. A clogged air filter in your furnace can also slow down the air passing through the coil.
To prevent this problem in the future, consider using higher efficiency air filters. Standard inexpensive spun glass filters are almost always less than 20 percent efficient. Some of them may only be 6 to 8 percent efficient. These filters are designed to protect your heating and air conditioning equipment, not cleanse the air.
You can purchase air filters that will not only protect your equipment, but also do a remarkable job of cleaning your interior air. These filters can trap very small particles of dust, pollen, mold and other irritants.
Some of these filters work much like the air and oil filters in your car. They are made using pleated filter paper. Others are made with fine synthetic polyester fibers. Higher efficiency air filters are sometimes coated with chemicals that can kill tiny microbes such as bacteria and mold.
There are several advantages to using these higher efficiency air filters. Not only will your heating and cooling equipment perform better, but your operating costs may also be lower. And your home’s air will be cleaner.
That $60 service call could have bought 10 filters.
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Have questions about the remodeling process? Write to Tim Carter, c/o The Chicago Tribune, P.O. Box 36352, Cincinnati, Ohio 45236-0352. Questions will be answered only in the column.
For a listing of manufacturers of higher efficiency air filters, for charts showing average particle sizes of household dusts, pollens, etc., and for other tips on air filtration, send $2 and your name and address to the above address. Ask for Builder Bulletin No. 74.
You also can obtain a free order form for a wide variety of individual job bid sheets by sending a business-size, self-addressed envelope to the same address.
