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AUTOMOTIVE
AIRCONDITIONING SYSTEM,
SERVICING, REPAIRING AND
MAINTENANCE

HISTORY
The main job of refrigeration and air-
conditioning system is to cool a
certain place, particles or a substance
down to, and maintain them at a
temperature lower than the normal
ambient temperature.

Air-conditioning can be define as a
process that removes heat. The
oldest and most well known among
refrigerants are ice, water and air. In
the beginning, the sole purpose was to
conserve food. The Chinese were the
first to find out that ice increased
the life and improved the taste of
drinks and for centuries people have
conserve food by freezing it, and it
was followed to discover by the
egyptians.

The idea of air-conditioning started
before a machine was created to
produce the cooling effect desired.
Evaporative cooling has been around
in one form or another for some time.
The Persians used a wind catcher
system to pull air down through a
tower and over water to provide
cooling in the summer months and
there are still many of these visible
today.

HVAC.ppt heating ventillation and air conditioning

Today, air-conditioning is regarded as
normal necessities. There are
countless applications for air-
conditioning now. Examples are
foodstuff conservation, process
refrigeration, ice production,
household air-conditioning, vehicle
air-conditioning and others. In fact,
it is difficult to imagine life without
air conditioning, refrigeration and
freezing, their impact on our
existence is much greater than most
people imagine.

THE REFRIGERATION CYCLE
• The LP/LT gas refrigerant enters the
compressor through the suction service
valve. The gas is drawn into the
cylinder of the compressor and
compressed by the piston which
becomes HP/HT gas refrigerant. It is
then discharged through the discharge
service valve into the condenser.

• In the condenser, the heat drawn from
the evaporator and from the heat of
compression are given up to air flowing
from the condenser thus making the
refrigerant change its state from gas to
liquid, but still in HP/HT but in liquid
form. It will then pass to the receiver
drier.

• The receiver drier stores the liquid refrigerant
and filter any dirt or tiny particles inside the
system. It is equipped with a fusible plug set
to discharge at around 350 F in the event of
abnormal increase of temperature. A sight
glass is also installed to provide a quick and
easy way of checking the refrigerant charge
of the system. If you see any sign of bubbles
or foam like substances, this indicate a
shortage of refrigerant. The refrigerant then
flows to the thermostatic expansion valve.

• The expansion valve has a sensing bulb
clamped to the suction line or after the
evaporator exit. The main function of the
thermostatic expansion valve is to control the
quantity of refrigerant in the evaporator coil,
as well as to prevent any liquid refrigerant
from reaching the compressor because the
liquid refrigerant is non-compressable and
can damage the compressor. After this, the
refrigerant will flow to the evaporator where
it will absorb heat from the air drawn by the
evaporator blower.

• A blower forces air from the interior of
the car through the evaporator and
circulate it to the interior of the car by
means of the front grilles of the panel
board of the evaporating unit. As the
liquid refrigerant is absorbing heat
inside the car compartment, the liquid
refrigerant, will change to gas
refrigerant and return through the
suction line to the suction service valve,
and the cycle is repeated.

• The continuous cycle, once repeated,
will very often drop the temperature in
the car which could reach an
uncomfortable level. To prevent this
condition, a thermostat will open the
magnetic clutch of the compressor to
disengage and stop the cycle.

PURPOSE OF AIRCONDITIONING
• Temperature control
• Rehumidify
• Air purification
• Air circulation
• It conditions the air

PHASES OF MATTER
• SOLID- compact material
• LIQUID- a substance that does not expand.
• GAS- a substance with the capacity to expand.
• PLASMA- distinct state of matter. Described as an
electrically neutral medium of positive and negative
particles. Heating a gas may ionize its molecules or
atoms (reducing or increasing the number of
electrons in them), thus turning it into a plasma,
which contains charged particles: positive ions and
negative electrons or ions.

HEAT EFFECTS CHANGE OF
STATE
• LIQUID – HEAT = SOLID
• LIQUID + HEAT = GAS
• SOLID – HEAT = SOLID
• SOLID + HEAT = LIQUID
• GAS – HEAT = LIQUID
• GAS + HEAT = PLASMA
• PLASMA + HEAT = PLASMA
• PLASMA – HEAT = GAS

UNIT OF HEAT
• BRITISH THERMAL UNIT (BTU)
– It is the amount of heat required to raised
one pound of water to one degree
fahrenheit. The more BTU a substance, the
greater will be the total heat and vice
versa.

METHODS OF HEAT TRANSFER
• CONDUCTION
• CONVECTION
• RADIATION
• In conduction, heat transfer occurs
between objects by direct contact. In
convection, the heat transfer takes
within the fluid. In radiation, heat
transfer occurs through electromagnetic
waves without involving particles.

TYPES OF HEAT
• SPECIFIC HEAT- is the amount of
heat required to raise the temperature
of 1 lb of a substance to 1 ˚F. It is also
the amount of heat available to a
specific substance.
• SENSIBLE HEAT- heat added to or
removed from a substance without
changing its state but changes occur in
its temperature level.

• LATENT HEAT- heat added to or
removed from a substance without
changing its temperature but its state
changes.
• SUPER HEAT- temperature of a gas
substance above its saturation change
of state temperature

TEMPERATURE
• It is the measurement of the intensity
movement of heat. The coldness and
hotness of a material.

UNIT CONVERSION
• CONVERSION FORMULAS:
-FAHRENHEIT TO CELSIUS;
˚C=5/9(˚F-32)
-CELSIUS TO FAHRENHEIT;
˚F=(9/5X˚C)+32
TO GET ABSOLUTE TEMPERATURE;
RANKINE(˚R) = ˚F +459
KELVIN (˚K) = ˚C +273

AUTHORS
• CELSIUS- Anders Celsius
• FAHRENHEIT- Daniel Fahrenheit
• RANKINE- William Rankine
• KELVIN- Lord Kelvin

FAHRENHEIT TO CELSIUS
212˚F TO ˚C
˚C=5/9(˚F-32)
˚C=.555(212-32)
˚C=.555(180)
˚C=100

CELSIUS TO FAHRENHEIT
100˚C TO ˚F
˚F=(9/5X˚C)+32
˚F=(1.8X100)+32
˚F=180+32
˚F=212

KELVIN TO RANKINE
100˚K TO ˚R
˚K=˚C+273 ˚ F=(9/5X˚C)+32 ˚R=˚F+459
˚C=˚K-273 ˚ F=[1.8X(-173)]+32 ˚R=-279.4+459
˚C=100-273 ˚ F=-311.4+32 ˚R=179.6
˚C=-173 ˚ F=-279.4

RANKINE TO KELVIN
100˚R TO ˚K
˚R=˚F+459 ˚C=5/9(˚F-32) ˚K=˚C+273
˚F=˚R-459 ˚C=.555(-359-32) ˚K=-217+273
˚F=100-459 ˚C=.555(-391) ˚K=56
˚F=-359 ˚C=-217

KELVIN TO FAHRENHEIT
200˚K TO ˚F
˚K=˚C+273 ˚F=(9/5X˚C)+32
˚C=˚K-273 ˚F=[1.8(-73)]+32
˚C=200-273 ˚F=-131.4+32
˚C=-73 ˚F=-163.4

FAHRENHEIT TO KELVIN
0˚F TO ˚K
˚C=5/9(˚F-32) ˚K=˚C+273
˚C=.555(0-32) ˚K=-17.76+273
˚C=.555(-32) ˚K=255.24
˚C=-17.76

RANKINE TO CELSIUS
180˚R TO ˚C
˚R=˚F+459 ˚C=5/9(˚F-32)
˚F=R-459 ˚C=.555(-279-32)
˚F=180-459 ˚C=.555(-311)
˚F=-279 ˚C=-172.6

CELSIUS TO RANKINE
60˚C TO ˚R
˚F=(9/5X˚C)+32 ˚R=˚F+459
˚F=(1.8X60)+32 ˚R=140+459
˚F=108+32 ˚R=599
˚F=140

KELVIN TO CELSIUS
150˚K TO ˚C
˚K=˚C+273
˚C=˚K-273
˚C=150-273
˚C=-123

CELSIUS TO KELVIN
10˚C TO ˚K
˚K=˚C+273
˚K=10+273
˚K=283

RANKINE TO FAHRENHEIT
120˚R TO ˚F
˚R=˚F+459
˚F=˚R-459
˚F=120-459
˚F=-339

FAHRENHEIT TO RANKINE
8˚F TO ˚R
˚R=˚F+459
˚R=8+459
˚R=467

PRESSURE
• It is the total force exerted on a
surface.
• Formula:
• P=F/A
• F=P(A)
• A=F/P
Where;
P=Pressure (psi)
F= Force (lb)
A= Area (Sq. in.)

TO GET THE PRESSURE
GIVEN: FORCE= 20lbs
AREA= 10sq.in
FORMULA: P= F/A
P=20Pounds/10sq.in
P=2Psi

TO GET THE FORCE
GIVEN: PRESSURE= 2Psi
AREA= 10sq.in
FORMULA: F= P(A)
F=2Psi(10sq.in)
F=20Pounds

TO GET THE AREA IN A GIVEN PRESSURE
GIVEN: FORCE= 20Pounds
PRESSURE= 2Psi
FORMULA: A= F/P
A=20Pounds/2Psi
A=10 sq.in

ATMOSPHERIC PRESSURE
• At sea level, the air with full height of the
atmosphere is weighing 14.7 pound. Thus the
pressure is 14.7 psi. At higher altitudes, there
is less weight so the pressure is less. Below
sea level, atmospheric pressure is more
than 14.7 psi. any conditions where pressure
is less than atmospheric pressure is called
vacuum. A perfect vacuum is the complete
absence of pressure.

AMBIENT TEMPERATURE
• It is the surrounding air temperature.

ATMOSPHERIC AIR
• Air surrounding the earth is called
Atmospheric Air.
• Atmospheric air is a mixture of 23% of
oxygen by weight and 75% of nitrogen by
weight, and the other gasses which is
composed of the remaining weight. These are
the carbon dioxide, ozone, carbon monoxide
and neon in small quantities. Moisture is
water in the form of gas

RELATIONSHIP: PRESSURE AND
TEMPERATURE
• Temperature and Pressure is directly
proportional. When the pressure rises,
the temperature also rises and vice
versa.

LAWS OF THERMODYNAMICS
• Zeroth Law of Thermodynamics
• First Law of Thermodynamics
• Second Law of Thermodynamics
• Third Law of Thermodynamics

ZEROTH LAW OF THERMODYNAMICS
“It state that temperature is the
indicator of thermal equilibrium in the
sense that there is no flow of heat
between two substance in thermal
contact that have the same
temperature.”
It is also called “THERMAL EQUILIBRIUM”

FIRST LAW OF THERMODYNAMICS
• It is the expression of the Law of
Conservation of Energy.
• It state the relationship between work,
heat and changes in the internal
energy.

SECOND LAW OF
THERMODYNAMICS
• It states that heat travels from high
temperature to low temperature of a
substance.

THIRD LAW OF THERMODYNAMICS
• It state that it is not possible/impossible
to lower the temperature of any
substance to absolute zero (T=0˚K) in
a finite number of steps.

HUMIDITY
- is the amount of water vapor in the
air. Water vapor is the gas phase of
water and is invisible. Humidity
indicates the likelihood of precipitation,
dew, or fog. Higher humidity reduces
the effectiveness of sweating in cooling
the body by reducing the rate of
evaporation of moisture from the skin.

• TYPES OF HUMIDITY
1. Absolute- is the water content of air.
2. Relative- is a function of both its water
content and temperature.
3. Specific- is a ratio of the water vapor
content of the mixture to the total air
content.

PROCESS OF AIRCONDITIONING
• Process of compression
• Process of condensation
• Process of filtration
• Process of expansion
• Process of evaporation

AIR-CONDITIONING SYSTEM: PARTS
• BASIC PARTS OF THE A/C SYSTEM
INCLUDES;
1. COMPRESSOR
2. CONDENSER
3. RECEIVER DRIER
4. EXPANSION VALVE
5. EVAPORATOR

A/C COMPRESSOR
• Also called as the “heart of the system”.
• It compresses the LP/LT gas
refrigerant.
• It also circulates the refrigerant
through out the system.

TYPES OF COMPRESSOR IN
GENERAL USE
A. Reciprocating
B. Swash plate
Other types;
1. Screw compressor
2. Rotary compressor
3. Centrifugal compressor
4. Scroll compressor

RECIPROCATING COMPRESSOR
• The reciprocating compressors are one
of the most widely used types of the
refrigerating compressors. They have
piston and cylinder arrangement like
the automotive engine. It has reed
valves that control the entrance and
exit of the refrigerant gas during the
pumping operation. Schrader valves are
mostly used for the service valves for
easy connection.

DURING SUCTION STROKE
• When the piston is on the down stroke,
the discharge reed valve is closed as
well as the suction service valve until
the piston reach the middle area of the
cylinder to create vacuum and to lower
the pressure inside the cylinder. The
suction reed valves will open when the
piston reach the middle area in the
cylinder, then allowing the refrigerant
to come in.

DURING DISCHARGE STROKE
• Wile the piston is on the upward stroke,
the suction reed valve will close while
the discharge reed valve will open when
the piston reach the middle area of the
cylinder to create compression, then
allowing the refrigerant to come out of
the cylinder.

SWASH PLATE COMPRESSOR
• It has an axial plate pressed to the
shaft. Instead of a crankshaft, produces
the reciprocating motion to the piston.
The flow of incoming and outgoing
refrigerant is controlled by the opening
and closing of reed valves which are
inside the compressor. There is one
common suction port and one common
discharge port in the compressor.

OTHER TYPES
SCREW
ROTARY
CENTRIFUGAL
SCROLL

MAGNETIC CLUTCH
• The main purpose of the magnetic
clutch is to engage and disengage the
compressor from the engine. It has a
drive belt pulley which is connected to
the engine.

COMPRESSOR OIL
• Is necessary to lubricate the seal,
gasket and other moving parts of the
compressor. A small amount of oil is
circulated through the system with
refrigerant. Only non-foaming oil
specially formulated for use in each car
airconditioner should be used. The oil
act as a lubricating agent and a coolant
in the compressor.

• Refrigeration oil is highly refined, it is
mineral oil with all impurities such as
wax and sulphur. Never use any kind of
motor oil except those oil recommended
by the manufacturer.

A/C CONDENSER
• The purpose of the condenser is to receive the high-
pressure gas refrigerant from the compressor and
change it to liquid by discharging heat into the
atmospheric air. It is the principle that heat flows from
warmer to a cooler substance. The greater the
amount of heat given of in the condenser, the
greater will be the cooling effect attainable by the
evaporator. It is installed usually at the front end of
the car radiator to enable forcible cooling by the air
drawn in the engine radiator fan and the air stream
created by the running of the car.

TYPES OF CONDENSER
1. Air-cooled – air-cooled condenser have
two basic types: Ram Air and the Forced air
condenser.
2. Water cooled- Not common used in A/C
system, mostly at bigger size refrigeration.
A. Ram air condenser depend upon car
movement to force a large of air pass the
aluminum fins and coils of the condenser.
The engine blower is used to increase air
volume at lower speeds.

The clutch-type blower is designed to allow
the blower blades to free-wheel at higher
speeds to eliminate blade drag. At lower
speeds, the blower fan clutch will engage the
fan to increase air flow over the condenser
and radiator coils.
B. Forced air condenser are usually used for
off-the -road units. It uses blower fan to move
a large volume of air over the condenser.

A/C RECEIVER DRIER
PARTS & FUNCTIONS
The receiver-drier is divided into three parts: the receiver,
the drier and the sight glass.
1. The receiver section - is a storage compartment that
accepts the proper amount of refrigerant.
2. The drier section – is simply a bag of desiccant; such
as silica gel, a chemical that absorbs and holds small quantities
of moisture that can damage the system.
3. The sight glass section – is provide to check if the
amount of refrigerant charged to the system is enough. If the
vapor bubbles appear in the sight glass this is an indication of
the lack of refrigerant.

FUSIBLE PLUG
The fusible plug protects from damage of the
other parts in the system when the temperature and
pressure inside the condenser or receiver go up
abnormally because of poor radiation of the
excessive heated components. The fusible plug is
soldered wherein it will melt at the temperature of 212
to 350 degrees fahrenheit.

A/C EXPANSION VALVE
• Is a metering device that lowers the
temperature of the liquid refrigerant
from the condenser. The orifice tube of
the expansion valve sprays out the high
pressure liquid refrigerant from the
condenser to the evaporator, thus
lowering the pressure. Expansion valves
are classified into two; internally
equalized and externally equalized.

A/C EVAPORATOR
• Evaporator is just an opposite of the
condenser. If the condenser discharges
heat and converts the gas refrigerant
into liquid, the evaporator absorbs heat
and converts the liquid refrigerant into
gas. The evaporator absorbs heat inside
the compartment of the car thus cooling
it on the level of human comfort.

• As the evaporator absorbs heat, the
100% liquid refrigerant sprayed by the
expansion valve to the evaporator is
converted to 100% gas refrigerant that
is induced to the compressor. If too
much refrigerant is sent into the
evaporator, it will not cool normally
because the pressure of the refrigerant
will be higher and it will not boil easily.

• If little refrigerant is supplied into the
evaporator, it is referred to as starved
evaporator. This condition will not
normally cool because the refrigerant
will boil off, long before it passes
through the evaporator.

A/C BLOWER FAN
• The fan motor or the blower fan forces
the passenger compartment of the car
through the evaporator and circulates it
to the interior of the car by means of
the grills. The motor input of the fan
blower ranges from 60W to 150W.

ACCUMULATOR
• Located between
evaporator and
compressor (low side)
• Primary function is to
separate the vapor
from the liquid and oil.

REFRIGERANT LINES AND
CONNECTIONS
• Suction line- Evaporator outlet to
compressor inlet.
• Discharge line- Compressor outlet to
condenser inlet.
• Liquid line- Receiver drier outlet to
thermostatic expansion valve.

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