Section 20A
Section 20A
Air Conditioning SystemAir Conditioning System
Introduction.Introduction. The air conditioning / heating sys-The air conditioning / heating sys-
tem provides the operator with a comfortabletem provides the operator with a comfortable
operating environment.operating environment.
Major ComponentsMajor Components(Illustration 20A-2)(Illustration 20A-2).. The airThe air
conditioning system consists of a wall-mounted airconditioning system consists of a wall-mounted air
conditioner / heater unit, condenser, compressor,conditioner / heater unit, condenser, compressor,
four 30 amp circuit breakers, and a heater shut-offfour 30 amp circuit breakers, and a heater shut-off
valve.valve.
Air Conditioner / Heater UnitAir Conditioner / Heater Unit (Illustration 20A-1)(Illustration 20A-1)..
The floor-mounted air conditioner / heater unit isThe floor-mounted air conditioner / heater unit is
capable of delivering 36,000 BTUs (37,980 kJ) ofcapable of delivering 36,000 BTUs (37,980 kJ) of
cooling capacity, 38,700 BTUs (40,830 kJ) ofcooling capacity, 38,700 BTUs (40,830 kJ) of
heating capacity, and is powered by 12 VDC fromheating capacity, and is powered by 12 VDC from
30 amp circuit breakers (CB21, CB22 and CB23).30 amp circuit breakers (CB21, CB22 and CB23).
The air conditioner / heater unit is a three speedThe air conditioner / heater unit is a three speed
unit with a unit with a preset thermostat. preset thermostat. The air conditioner The air conditioner //
heater unit has a cool / heat switch that allows theheater unit has a cool / heat switch that allows the
operator to select for cooling or heating of the cab.operator to select for cooling or heating of the cab.
The air conditioning system is charged withThe air conditioning system is charged with
approximately 4.25 lbs. (1.9 kg) of R134a Freon.approximately 4.25 lbs. (1.9 kg) of R134a Freon.
NOTE:NOTE: The Clean Air The Clean Air Act, passed Act, passed in 1992, speci-in 1992, speci-
fies that anyone who works on vehicle air condi-fies that anyone who works on vehicle air condi-
tioning systems must be certified by an EPAtioning systems must be certified by an EPA
approvedapproved agencyagency
warm, high pressure liquid (to the expansionwarm, high pressure liquid (to the expansion
valve). valve). The drier is The drier is equipped with a equipped with a binary switchbinary switch
which protects the compressor.which protects the compressor.
The binary switch is normally closed when theThe binary switch is normally closed when the
system pressure is within operating specifications.system pressure is within operating specifications.
The binary switch will open when the system pres-The binary switch will open when the system pres-
sure exceeds 312 sure exceeds 312 psi (22 bar). psi (22 bar). The binary sThe binary switchwitch
will not close again until the pressure has droppedwill not close again until the pressure has dropped
below 225 below 225 psi (16 psi (16 bar). bar). When the When the pressure dropspressure drops
below 2 psi, below 2 psi, the binary sthe binary switch will witch will open. open. TheThe
binary switch will not close again until the pres-binary switch will not close again until the pres-
sure is above 28 sure is above 28 psi (2 bar). psi (2 bar). The binary switchThe binary switch
can be replaced without recovering the refrigerant.can be replaced without recovering the refrigerant.
The binary switch is located in the air conditionerThe binary switch is located in the air conditioner
unit on tunit on the high presshe high pressure side. ure side. The fitting The fitting thatthat
holds the binary switch is equipped with a checkholds the binary switch is equipped with a check
valve, that prevents the high pressure coolantvalve, that prevents the high pressure coolant
from exhausting if the switch is removed.from exhausting if the switch is removed.
Evaporator / Heater Coil.Evaporator / Heater Coil. The The evaporator evaporator / / heat-heat-
er coil is located inside the air conditioner / heaterer coil is located inside the air conditioner / heater
unit. unit. The evaporator The evaporator and heater coils and heater coils are inte-are inte-
grated into grated into one unit. one unit. The evaporator The evaporator coil changescoil changes
the warm, metered pressure liquid refrigerantthe warm, metered pressure liquid refrigerant
(from the expansion valve) into a cold, low pres-(from the expansion valve) into a cold, low pres-
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