Generally speaking, all heating and cooling components (except
the thennostat) are housed in sheet steel cabinets. The cabinet
helps protect the components and adds to the attractiveness of
the units.
The heating unit or furnace cabinet is normally located indoors. It
has connection provisions for attaching the cooling coil, supply air
plenum and return air plenum. The cabinet also contains openings
or knockouts for electrical service and required plumbing.
Designed into the cabinet are removable access doors to allow for
servicing the unit. The front door to oil and gas furnaces is slotted
to allow combustion air to enter (this is not necessary on electric
furnaces, since no fuel is burned).
Since the cooling system’s outdoor unit is exposed to the weather
elements and in the public eye, it is especially important the
cabinet is durable, weather resistant and attractive in appearance.
Like the furnace cabinet, the outdoor cooling unit cabinet has
service access doors and provisions for electrical and mechanical
(i.e. refrigerant line) connections.
Gas is fed into the burners and ignited by a pilot flame on a call for
heat from the thermostat. The burning gas warms the heat
exchanger and the blower distributes the heat throughout the house.
The oil heat section is made up of a firebrick pot and steel heat
exchanger. When the thermostat calls for heat, oil is pumped
through a nozzle and ignited by a spark from a set of high voltage
electrodes. A ball of fire is produced in the firebrick pot, which
heats the steel heat exchanger. The blower then moves this heated
air to the various distribution points.
Temperature Treatment Section
The temperature treatment section of a heating or cooling unit is
that portion of the unit which produces the heating or cooling. (All
types of heating units and cooling systems are discussed in greater
detail in the sections that follow.)
Heat Sections
Most residential furnaces use either natural or liquefied propane
(LP) gas, oil or electricity as their source of heat.
The heat section of an electric furnace consists of one or more
electric heating elements. The element is much like that in an
electric toaster, only bigger. When the thermostat demands heat, an
electrical resistance to the flow of electricity in the element
produces heat. The heated air is moved by the furnace blower
through the ducts and distributed to points all over the home.
The heat section of a gas (either natural or propane) furnace
consists of a steel heat exchanger and gas burners. The
burners fit in a cavity at the bottom of the heat exchanger.
Bard Total Electric Features
Built-In Cooling Coil Compartment—Slidein type for easier conversion to summer cooling,
Accomodates 1-1/2, 2, 2-1/2, and 3 ion
cooling coils.
Controls—On demand from the wall
thermostat, the heating elements are energized
by electrical contactors. The 15 thru 30K.W
versions have the blower motor interlocked with
each stage for safety. Easily two staged.
Limit Switch—Thermal snap disc in each
heating element shuts oif power automatically
if system air temperature becomes excessive
Built-In Transformer—Provides power
supply for heating and optional cooling controls
Blower Relay—Provides automatic blower
speed change-over to meet heating and cooling
air delivery requirements.
Branch Circuit Fusing—Factory installed in
models rated over 48 amps.
Heating Elements—Nickel-chrome wire with
individual fusible links for long life. Entire
assembly slides out for easy maintenance.
Motor—Multi-speed for both heating and
cooling.
Blower—Heated air is quietly circulated by
large volume centrifugal blower that is matched
to the electrical heating system for efficiency.
Slides out for easy maintenance.
Fillers—Twin permanent type slide out from
front for easy cleaning on all models except
Models EFC5 andEFClO.
Typical Gas Furnace
Sled Cabinet is accoustically and ihennaUy
insulated for quieter operation and minimum
heat loss.
Filter is extra large for better system air cleaning
efficiency.
Heat Exchanger efficiently extracts all usable —
heat for greater fuel economy.
Safety Pilot provides 100% automatic shut-o£f
for safely.
Mono“.Jet® Burner provides ease in adjustment
and has uniform flame distribution for maximum
efficiency.
Powerful Blower Motor is resilient mounted for
quieter operation.
Model G152
All components are easily accessible for service and inspection.
Typical Oil Furnace
Bard Cooling Coils with plenum and system matched
components are optional for converting to summer
air conditionirrg.
Electrostatic Air Cleaner traps up to 95% of air-bome
dust, bacteria-size particles, smoke, odors and 99%
pollen. This optional accessory may be installed with
furnace or added later.
Fan and Limit Control with helcx element
automatically controls blower and burner operation.
Blower is capaci^ matched to heating components and
quietly circulates air throughout system.
Typical Installations
steel Cabinet is accoustically and ihermaOy
insulated for quieter operation and minimum heat
loss.
Fan and Limit Control with helex element
automatically controls blower and burner
operation.
Heat Exchanger provides more heating surface
for efficiency.
Motor has resilient base mounting for both
heating or cooling applications.
Blower is centrifugal type, dynamically balanced
and mounted on rubber grommets for quieter
operation.
Burner is designed for super-quiet efficiency.
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.
WARNING
A
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.
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