Bard 2100-066 Rev. A - Manual (Page 5)

Cooling Section
This cooling section in a typical split-system application is the
indoor evaporator coil. This coil is located in the supply plenum of
the furnace. Stated simply, cool refrigerant is pumped through the
evaporator coil by the cooling unit. The refrigerant in the
evaporator coil removes heat from the air, and the furnace blower
distributes this cool air to the conditioned spaces.
Blower
The device which moves the treated air to points throughout the
home is called the blower, The blower consists of a wheel with air
scoops sometimes called a scroll and a motor to drive the wheel.
There are two types of blowers; a belt drive and a direct drive.
Illustrated here are typical gas-fired and oil-burning
counterllow furnaces.
Belt Drive Blower
A belt runs from a pulley mounted on the motor to a pulley
mounted on the blower wheel, All moving parts are anchored on a
rigid U-ffame, which in turn is fastened on resilient mountings to
the furnace. The design of this frame insures easy adjustment and
alignment of pulleys and belts for optimum performance. Varying
amounts of air can be moved by a belt drive blower, depending
upon the motor pulley size adjustment (see diagram). The pulley
can be made larger by screwing one side of the pulley inward
toward the other side; this causes the blower wheel to rotate faster.
Screwing one side outward from the other side reduces the pulley's
effective circumference, which in turn reduces the speed of the
blower wheel. If volumes of air are desired, which caimot be
obtained by motor pulley adjustment, the motor or blower pulleys
themselves can be changed,
NOTE: A larger pulley might also necessitate a larger motor.
Direct Drive Blower
The direct drive blower motor is mounted inside the blower and is
directly linked to the blower wheel. Air volume changes are made
by electrically varying the speed of the motor. The speed in direct
drive blowers is changed depending upon which of several wire
leads (speed taps) coming from the motor are used. Usually two to
five speeds can be obtained by wiring the hot wire to the desired
speed tap lead and the neutral wire to the common motor lead. The
unused hot wire leads must be taped separately to prevent coming
in contact with an electrical ground. The rotating motor produces a
back voltage (emO of approximately 200 vac through
electromagnetic induction.
A
WARNING
Use caution when handling these leads with 200 vac
electrical potential. If not taped, they could cause arcing
to ground, shorts or serious electrical shocks.
Filter
A filter is the device in a forced air heating or cooling unit which
mechanically screens out dust, dirt, lint and other impurities from
the Systran's airstream.
The filter is usually located just upstream from the blower, in the
return air side of the system. A fiberglass media commonly acts as
the screen, cleaning the air before it is recirculated throughout the
system by the blower.
A dirty filter greatly reduces the system's airflow, which greatly
reduces the operating efficiency of the heating or cooling unit. For
this reason, The homeowner should be instructed to check the filter
monthly and clean or replace it if necessary. (Never reuse a dirty
filter by turning it bottomside up; this will result in the collected
dirt being dumped back into the airstream.)
Two types of filters are the disposable and the permanent. Most
slab filters are disposable, consisting of rectangular fiberglass
screen in a cardboard frame. These come in a variety of sizes to fit
completely across the airstream. Arrows marked on the frame
indicate correct placement with respect to system airflow. When
the filter becomes dirty, it should simply be removed and a new one
put in its place. A nondisposable slab filter uses a polyurethane
media encased in a metal frame. When this filter becomes dirty, the
media may be cleaned (washed or vacuumed) and reused.
Thermostat
The thermostat is a heat sensitive switch that serves as the
automatic control center for heating and cooling system operation.
Since the thermostat was discussed in detail in a previous manual,
its story will not be repeated here. The student should review the
manual on thermostats if necessary.