the location of filters and different types of
furnaces. (See figure on left).
Air filters are provided on all forced air furnaces to remove dirt and lint from heated air. (See figure on left). This keeps the fan, heat exchanger and air conditioning coil clean. It also helps clean the air of your home as air circulates through the system (Note the direction of the air flow).
The standard filter on most furnaces is a nominal 1"-thick media filter. (See figure on right). Usually, this filter is made of fiberglass. The filter should be changed when it is visibly dirty - usually every one month or two, depending on the quality of the filter and the amount of dirt in your home's air. Children, pets, plants, and activity tend to produce more dirt that finds its way into the heating system.
careful about the direction of the airflow through
the filter. Filters are designed to be installed
with one particular side facing the air stream.
Most filters have directions or an arrow telling
you which side should be installed toward the
furnace. The arrow is the direction of the airflow
and should be toward the base or the fan of the
Remember: the furnace filter is also used when you operate the fan and/or central air conditioning, so you should check on the filter during the summer, too.
based on the type of filter, how often the
unit is running (heating and cooling), and
how you use your home. The three basic
types of filters are media, electronic,
I recommend that you try one of the pleated paper filters. These catch more dirt than inexpensive fiberglass filters. (See figure on left). Some even have a static charge to attract dirt. Others have a carbon filter content. Paper filters cost between $3 and $15 and can be found in most hardware stores. You will need to change this type of filter more often because it collects more dirt.
Washable filters can be made of foam or woven synthetic fiber. They are about as effective as inexpensive fiberglass filters. You can improve the efficiency of a foam filter by spraying it with a special filter coating; this oily/waxy spray helps the filter hold dirt better.
PLEATED, 4- TO 6-INCH THICK
A big improvement over the standard 1" -thick filter is a pleated fiberglass or paper filter.
Often, the pleated paper filter is housed in a 6" -thick frame. The paper filter is very fine, and it catches smaller particles of dirt and dust. This type of filter is normally changed once per year, and you replace only the paper element. (See figure on right).
A pleated fiberglass filter often is mounted in a throwaway paper frame. The entire unit is replaced about once a year.
Electronic filters use electrically charged metal plates and wires that attract dirt. (See figure on left). These filters can remove very small particles from smoke and pollen which aren't caught by standard filters. If you have respiratory problems or are sensitive to dust or pollen, you may want to use this type of filter.
filters cost more than $600 to install.
Maintenance involves washing the interior frame
and metal plates and wires with detergent or
running them through a dishwasher. Most electronic
filters have a metal pre-filter that also must be
washed. For more specific cleaning instructions,
contact a heating contractor or the filter
manufacturer. The references section includes
Electrostatic and Electronic Filters
Many types of washable filters have multiple layers of filtering material; vendors claim these layers contain an electrostatic charge that attracts and traps dirt more effectively than a standard media filter.
Several companies also make a 1" -thick electrostatic/electronic filter as a direct replacement for throwaway filters. This filter may have an electronic power supply and may require particular maintenance procedures.