Cub Cadet 8454 Service Manual page 325

C. OPERATION PRINCIPLES OF SYSTEM
COMPONENTS
a . Refrigerant
In order to accomplish the intrinsic function of air-con-
ditioning system, it is needed to use the suitable re-
frigerant - which features relatively low temperature
boiling point and the desirable safety and stability. The
refrigerant to be used in the air-conditioning system is
HFC-134A.
Ref.) In order to observe the environment regulations,
the air emission of the refrigerant including HFC-134A
is prohibited.
NOTE:
The refrigerant HFC-134A is not available to be com-
patible with CFC-12. It is not available to replace the
HFC-134A refrigerant with CFC-12 refrigerant or test
the system by using the gauge or equipment that is
used for CFC-12 before as it may affect the damage to
the system. The HFC-134A refrigerant is stable at all
operation temperature and available to absorb lots of
heat. The boiling point of HFC-134A is -22°C (-15°C).
b. Compressor
The compressor that is a major component of air-con-
ditioning system, shall be installed on the upper part
of the left side of engine.
The compressor is divided into the low-pressure side
and high pressure side and originally is one pump
which has two functions.
(1) The function to increase the refrigerant tempera-
ture higher than the ambient temperature.
(2) The function to circulate the necessary capacity of
refrigerant through the system.
c. Condenser & Receiver Drier
The condenser is located in front of tractor and con-
sists of continuous revolution of coil mounted on the
series of fine cooling pin, and offers maximum heat
movement in the minimum space.
The condenser receives a hot and high-pressure steam
of refrigerant from the compressor. The hot steam
passes the condenser coil and the air outside passes
the condenser by the cooling fan of engine.
The heat moves from the hot steam of refrigerant to the
cold air outside and flows to the coil and pin of the
condenser.
When the steam of refrigerant reaches the pressure,
the temperature causes the change of state and a large
amount of heat moves to the air outside and the refrig-
erant is changed to the hot and high-pressure fluid.
The hot fluid of refrigerant continues the receiver drier
which is filtered and dried and removes all humidity
before passing the outlet line and automatic tempera-
ture control extension valve.
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As the drier contains a drying agent, it absorbs all hu-
midity in the system and the filter prohibits the external
particles to enter in.
Ref.) The humidity of air-conditioning system is abso-
lutely harmful. The humidity that is not absorbed by a
drying agent shall be circulated with a refrigerant and
able to cool down the hole of automatic temperature
control extension valve. Such action prevent the flow of
refrigerant and stop the operation of cooling. The hu-
midity may generate the corrosive acid caused by a
reaction of HFC-134A refrigerant and lubricant.
A drying agent is available to absorb the limited amount
of humidity before reaching to the point of saturation.
Thus, it is needed to change the receiver drier after
replacing or repairing the system components.
d. Extension Valve
The extension valve is located near the pressure line
which is connected to the receiver drier, and its func-
tions are as follows:
-
-
-
e . Vaporizer
The vaporizer is located on the upper part of the cabin
and consists of continuous revolution of coil mounted
on the series of fine cooling pin and offers maximum
heat movement in the minimum space.
The low-temperature refrigerant of vaporizer absorbs
the heat from hot air that exists in the space of operator
and accordingly cools down the air.
f. Blower Fan
The blower fan draws out the air through ventilation
filter hole from outside the cabin and makes the hot air
cross the vaporizer before flowing into the cabin
through the radiation hole.
The blower motor is adjusted by 3 stages. The switch
changes the speed of fan by using various resistors.
The high speed blower offers the maximum volume of
the circulated air while the low speed blower makes
the air to contact the cooling pin and the coil of vapor-
izer for a long time which results in the failure to make
the hotter air and the colder refrigerant. Therefore, the
coldest air temperature will be acquired when the
blower fan operates at the lowest temperature.
To change the fluid refrigerant from high-pressure
and low temperature fluid to the injected fluid with
low pressure and low temperature.
The valve that is controlled by automatic tempera-
ture control in the extension valve shall adjust the
capacity of fluid refrigerant that passes through the
hole and make the refrigerant be evaporated com-
pletely in the evaporator.
The valve reacts according to the change of cooling
condition but if the cooling increase is needed, the
valve will be open to increase the flow of refrigerant
and on the contrary, if the cooling reduction is
needed, the valve will be closed to reduce the flow
of refrigerant.
CABIN SYSTEM
9-11