Principles Of Refrigeration - Komatsu 830E Shop Manual

(HFC) refrigerant, commonly identified as HFC-134a or R-134a, is being used in most current mobile air condition-
ing systems. Additionally, the practice of releasing either refrigerant to the atmosphere during the charging/
recharging procedure is prohibited.
These restrictions require the use of equipment and procedures which are significantly different from those tradi-
tionally used in air conditioning service techniques. The use of new equipment and techniques allows for complete
recovery of refrigerants, which will not only help to protect the environment, but through the "recycling" of the refrig-
erant will preserve the physical supply, and help to reduce the cost of the refrigerant.
OPERATOR CAB AIR CONDITIONING
Mining and construction vehicles have unique char-
acteristics of vibration, shock-loading, operator
changes, and climate conditions that present differ-
ent design and installation problems for air condi-
tioning systems. Off-highway equipment, in general,
is unique enough that normal automotive or high-
way truck engineering is not sufficient to provide the
reliability to endure the various work cycles encoun-
tered.
The cab tightness, insulation, and isolation from
heat sources is very important to the efficiency of
the system. It is advisable to close all vents, even
the intakes of pressurization systems, when there
are high humidity conditions.
The general cleanliness of the system and compo-
nents is important. Dust or dirt collected in the con-
denser, evaporator, or air filters decreases the
system' s cooling capacity.
The compressor, condenser, evaporator units,
hoses and fittings must be installed clean and tight
and be capable of withstanding the strain and abuse
they are subjected to on off-highway vehicles.
Equipment downtime costs are high enough to
encourage service areas to perform preventative
maintenance at regular intervals on vehicle air-con-
ditioning systems. (Cleaning, checking belt tight-
ness, and operation of electrical components).
M9-2

PRINCIPLES OF REFRIGERATION

A brief review of the principles of air conditioning is
necessary to relate the function of the components,
the technique of troubleshooting and the corrective
action necessary to put the AC unit into top operat-
ing efficiency.
Too frequently, the operator and the serviceman
overlook the primary fact that no AC system will
function properly unless it is operated within a com-
pletely controlled cab environment. The circulation
of air must be a directed flow. The cab must be
sealed against seepage of ambient air. The cab
interior must be kept free of dust and dirt which, if
picked up in the air system, will clog the intake side
of the evaporator coil.
AIR CONDITIONING
Air conditioning is a form of environmental control.
As applied to the cab, it refers to the control of tem-
perature, humidity, cleanliness, and circulation of
air. In the broad sense, a heating unit is as much an
air conditioner as is a cooling unit. The term "Air
Conditioner" is commonly used to identify an air
cooling unit. To be consistent with common usage,
the term "Air Conditioner" will refer to the cooling
unit utilizing the principles of refrigeration; some-
times referred to as the evaporator unit.
Air Conditioning System
for HFC 134a Refrigerant
05/02 M09010