Komatsu 830E-AC Shop Manual page 936

AIR CONDITIONER SYSTEM
COMPONENTS
Compressor (Refrigerant Pump)
The compressor is where the low pressure side of
the system changes to high pressure. It concentrates
the refrigerant returning from the evaporator (low
side) creating high pressure and a temperature much
higher than the outside air temperature. The high
temperature differential between the refrigerant and
the outside air is necessary to aid rapid heat flow in
the condenser from the hot refrigerant gas to much
cooler outside air.
To create high pressure concentration, the compres-
sor draws in refrigerant from the evaporator through
the suction valve and during compression strokes,
forces it out through the discharge valve to the con-
denser. The pressure from the compressor action
moves the refrigerant through the condenser,
receiver-drier and connecting hoses to the expansion
valve.
The compressor is driven by the engine through a v-
belt driving an electrically operated clutch mounted
on the compressor drive shaft.
Service Valves
Quick-connect hose end fittings with integral service
valves attach to system service ports for servicing
the unit. A manifold gauge set is connected into the
system at the service valve ports and all procedures,
such as discharging, evacuating and charging the
system, are performed through the service valves.
Condenser
The condenser receives the high pressure, high-tem-
perature refrigerant vapor from the compressor and
condenses it to high pressure, hot liquid.
It is designed to allow heat movement from the hot
refrigerant vapor to the cooler outside air. The cool-
ing of the refrigerant changes the vapor to liquid.
Heat exchange is accomplished using cooler air flow-
ing through the condenser. Condenser cooling is
achieved by air flowing from the radiator fan along
with ram air provided by vehicle movement. The radi-
ator fan moves more than 50% of condenser air flow
unless travel speed is at least 25 mph.
N4-10
Ram air condensers depend upon the vehicle move-
ment to force a large volume of air past the fins and
tubes of the condenser. The condenser is usually
located in front of the radiator or on the roof of the
truck.
Condensing of the refrigerant is the change of state
of the refrigerant from a vapor to a liquid. The action
is affected by the pressure of the refrigerant in the
coil and air flow through the condenser. Condensing
pressure in an A/C system is the controlled pressure
of the refrigerant which affects the temperature at
which it condenses to liquid, giving off large quanti-
ties of heat in the process. The condensing point is
sufficiently high to create a wide temperature differ-
ential between the hot refrigerant vapor and the air
passing over the condenser fins and tubes. This dif-
ference permits rapid heat transfer from the refriger-
ant to ambient air.
Receiver-Drier
The receiver-drier is an important part of the air con-
ditioning system. The drier receives the liquid refrig-
erant from the condenser and removes any moisture
and foreign matter present which may have entered
the system. The receiver section of the tank is
designed to store extra refrigerant until it is needed
by the evaporator. The storage of this refrigerant is
temporary and is dependent on the demand of the
expansion valve.
A desiccant is a solid substance capable of removing
moisture from gas, liquid or solid. It is held in place
within the receiver between two screens, which also
act as strainers.
The receiver-drier is also equipped with a sight glass
and a moisture indicator. The sight glass can give a
good indication of the charge of the system. If the
sight glass is not clear, the system is low on refriger-
ant.
The moisture indicator is a device to notify service
personnel that the drier is full of moisture and must
be replaced. The indicator is blue when the compo-
nent is free from moisture. When the indicator turns
beige or tan, the drier must be replaced.
Operator Comfort 10/06 N04031