3.SAFETY PRECAUTIONS
4.ELECTRICAL CONTROL DEVICES
THERMOSTATS
e
n
RELAYS
HEATER CONTACTOR
5. APPLICATION
which controls the heater.
The coil uses 24 volts but the contacts carry line voltage .The heater contactor is a large relay,
There are similar overloads in the indoor air handling portion with the electric resistance heaters. The
NOTE: Never disconnect or wire around a safety device. First determine why it opened, then replace it
with a properly rated part.
indoor blower motor has an internal overload. The electric elements use two types of protectors, both
protector and must be replaced upon opening. Limit controls are thermal discs that automatically reset.
replaceable. Some electric heat sections use fusible links. They are a one time over-temperature
Normally, limit controls open and stop the temperature rise before the fusible links open.
OVERLOADS AND LIMITS
ƽ Follow the manufacturer’s instructions when making repairs, installing replacement parts and
ƽ Use only authorized factory parts.
ƽ Always use industry-recognized service practices in the maintenance, adjustment and repair of the
products covered in this manual.
ƽ Always wear safety glasses when handling refrigerant and peforming brazing operations.
CAUTION: please read all instructions prior to
installing, operating, maintaining or repairing the
product.
WARNING: THE MANUFACTURER’S WARRANTY DOES NOT COVER DAMAGE TO CAUSED BY
THE USE OF ANSUTHORIZED COMPONENTS OR ACCESSORIES, THE USE OF SUCH
UNAUTHORIZED COMPONENTS OR ACCESSORIES MAY ENDANGER LIFE AND
OR INJURY RESULTING FROM THE USE OF SUCH UNAUTHORIZED COMPONENTS OR
PROPERTY. THE MANUFACTURER DISCLAIMS ANY RESPONSIBILITY FOR SUCH LOSS
ACCESSORIES
performing system maintenance.
In the cooling mode, the thermostat calls for cooling by energizing the compressor contactor and the
indoor blower control. The indoor blower can operate continuously by setting the thermostat subbase fan
switch to the “ON” position.
subbase selection information found in the wiring diagram booklet.
various manual changeover, auto changeover and set-back thermostats or see the thermostat and
accessible by the consumer. Contact your local distributor for information on part numbers of
Thermostats are the most obvious control in the air conditioning system because these controls are
Generally relays used in air conditioning use 24VAC coils. Contact voltage may be either low or line voltage.
Relays provide a method for control switching. Relays may switch either low(24VAC) or line voltage.
Before specifying any air conditioning equipment, a survey of the structure and a heat gain calculation
The cooling load calculation determines the unit size. There are two capacities that enable the
must be made. A heat gain calculation involves identifying all surfaces and openings that gain heat from
the surrounding air and quantifying that heat gain. The heat calculation also calculates the extra
heaty load caused by sunlight and by humidity removal. These factors must be considered before
selection an air conditioning system to provide year round comfort. The Air Conditioning Contractors
cooling load.
of America (ACCA) J Manual method of load calculation is one recognized procedure for determining the
Sensible heat is the heat energy
measured on the dry bulb thermometer.
equipment to provide comfort. The first is sensible capacity.
5
Central Air Conditioning Model: Air Handler, HB-D series
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