|  Check
the Switches
While it is probably
okay, it’s not a bad idea to stroll over
to your breaker panel and make sure the breaker marked “Furnace” is
on. If your A/C was on recently, you can rest assured the breaker
is okay. Then head back to the furnace and look for the switch
that controls
the electricity to the unit. Most furnaces have a switch that looks like a light switch controlling
the electrical supply. In a new house, the switch is often on a
wall or a support about 6 feet above the floor, near the furnace.
In an older
house, the switch is often on the basement ceiling, or high on
a wall, near the bottom of the basement stairs. This allows
you to shut off the
furnace quickly in the event of an emergency, without having to
get near the furnace.
Now that you finally know what that mystery switch is, check
to see if it is ON. If not, the heat will not come on no matter
how high you set the thermostat. It is embarrassing to write a $75
cheque
for
a technician to come to your house and flip a switch.
It’s now time to focus on the two primary maintenance jobs for
furnace owners: the air filter and the humidifier. We’ll talk about
the air filter now and save the humidifier for the next issue.
The Air Filter
When the outside
air makes its way inside, pollutants like dust, dander and spores
are added to the air which has already
been exposed
to urban car exhaust, smog, dirt and pollen. The result is a
thick, soupy haze…that
is entirely normal. While most people aren’t bothered by the
usual level of air-borne particulates, some are more sensitive,
and everyone is affected if the level becomes excessive. To remove
many
of the larger particles from the air, your furnace is equipped
with a filter. 
Most filters are simply screens of paper, metal or plastic mesh that
allow air through but trap most of the dirt. Some of these are thicker
for more surface area, and some have specially treated media. Electronic
air filters use electricity to electrostatically attract even smaller
particles. They have a metal cover, an on/off switch, and may have
an operation light. There are those that dispute the quality of the
air cleaning abilities of standard household filters. These people
usually sell high-end systems. For most houses the normal filters will
do, and if nothing else they help keep the furnace itself free of massive
dust accumulations.
Where is It?
The furnace filter
is typically a one to two-inch wide slot (for conventional filters)
or a six to eight-inch wide slot
(for electronic filters)
in the ductwork immediately beside the furnace air return duct.
If you don’t see such a slot, your furnace’s air filter
is accessed only by removing the furnace and/or fan compartment
cover. Turn OFF the switch to the furnace before removing any covers.

What do I do?
Once you have located
the filter, pull it out to have a look. Turn off the switch on the
electronic air filter
before opening the
cover. For a regular filter, if the mesh looks dirty and/or
the unit is more than 3 to 6 months old, throw it out (paper
media or fiber
glass) or clean it (metal or plastic media). For an electronic
filter, make sure you turn off the unit’s power switch. There
will be two washable metal screens called pre-filters, then two electronic
cells looking like layers of metal plates. These can all be
soaked
and washed, every one to three months. Careful of the fine
wires running down one side of each cell…they are easy to lose
or break. Regular cleaning of the air filter is important for
your furnace
and your lungs.
Line
drawings are from Carson Dunlop's The Home Reference Book

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