Advice from Contractors:
Get Ready to Chill This Summer
By Rick Dole
Don't wait until
the first 90-degree day of the year to check your air conditioning system.
You'll already be miserable, and HVAC professionals will be very busy.
Now is the time to do some maintenance or consider a new unit, if needed.
Air Conditioning 101
An air conditioner
cools an area by transferring the heat to a less objectionable place,
usually outside. The unique elements that make the air conditioning system
work are the compressor, the refrigerant gas, and the expansion valve.
When refrigerant is compressed into a hot liquid and forced through a
tiny hole in the expansion valve, it changes (flashes) into a very cold
gas. It is then able to cool the room by absorbing heat.
With central air
conditioning, the condenser unit that sits on a cement pad outside of
your house contains the compressor, the condenser coil, and evaporator
coil, as well as the electrical connections and controls. The condenser
and evaporator coils are heat exchangers (similar to car radiators). The
small copper line going into the house is the high-pressure line to the
expansion valve. The larger suction side copper line next to it flows
to the intake (suction) side of the compressor.
fan filter on a central air system should be changed at least once a year,
and that is a good time to check the condensation drain as well. It's also
important to keep leaves and other debris away from the condenser coil.
The condenser unit can be opened for better access to the condenser coil,
but always shut off the power first.
The evaporator coil
is often inaccessible, but the filter can be changed. If you are lucky
and have access, check to make sure the airflow through the coil is not
restricted by a buildup of lint and dirt. Compressed air is best when
cleaning coils, but a soft brush and vacuum also will work. Be very careful
not to mash the fins, or the coil will lose efficiency.
Keep away from
Keep away from
Shut off the
before cleaning the coils or performing any work on the
Use eye protection
when cleaning the coils.
When to Call in the Pros
A properly installed air conditioning system will last many years, but it
may occasionally have trouble. Handy do-it-yourselfers can do some troubleshooting,
but if you are inexperienced, it is easy to short out a compressorand
very expensive to replace it. A good source of available local professionals
is ImproveNet, which conducts independent screening of the professionals
in its network. (Editor's note: Visit our
Find a Contractor
page to use this free service.)
If your unit is not
cooling properly, it means there is not enough of a heat exchange in the
condenser coil. This is usually because of obstructed airflow through
the coil, or because the condenser fan doesn't work. Another cause could
be a shortage of refrigerant because of a leak in the system. If you've
checked that airflow across the coil is not hampered with leaves and other
debris, call a professional before going any further on your own.
Finally, if you plan
to replace or install a new air conditioner any bigger than a window unit,
you need to contact a qualified air conditioning contractor. Installation
requires special equipment and, in many areas, a license to work with
refrigerant. If the installation is done improperly, the compressor will
have a very short life.
Rick Dole is a contractor in San Jose, California.
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