Troubleshooting package-type air-conditioning units(PACU) / commercial refrigeration equipment (CRE)

Answer Key 2

Identifying Hermetic Compressor Terminal

1. The table shown below is an obtained test result of a 1.5 hp compressor, it reveals
that the resistances are;

Terminals Resistance
12 3.5 ohms
13 1.5 ohms
23 5 ohms

2. From the table terminal 2 and 3 is the highest resistance either of this terminal is start
or run, therefore terminal 1 is COMMON.

3. Terminal 1 and 3 is the lowest resistance, this indicates that this is the run winding.
Since terminal 1 is already pin pointed as COMMON terminal, therefore terminal 3 is
RUN terminal.

4. The configuration of terminals therefore are as follows:

COMMON
1

2 3

START RUN

TESDA-GOTEVOT 48
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Assignment Sheet 3

Determining Hermetic Compressor Terminal

Objectives: At the end of this activity, the learner/trainee should be able to:

o Tag the three terminal using number or letter.
o Obtain resistance results from the three terminals of compressor
o Identify the terminals.

Equipment: - 1 unit
o Multi meter 1 unit
o compressor
- 1 pc
Materials: 1 pc
o rug 1 pc
o sand paper
o pencil/ball pen - 1 pc
o masking tape 1 pc
1 pc
Tools: 1 pc
o Phillips screw driver
o Flat screw driver - 1 pair
o Long nose pliers - 1 pc
o Diagonal cutting pliers

Personal Protective Equipment:
o Gloves
o Goggles

Procedures:

1. Ask your instructor for 1 unit hermetic compressor.
2. Obtain the necessary tools materials and equipment.
3. Take the necessary data to identify the terminals of motor.
4. Upon completion, ask your instructor to check your work.
5. Perform housekeeping

TESDA-GOTEVOT 49
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Operation Sheet 7

Testing Compressor Motor Winding

Objectives: At the end of this activity, the learner/trainee should be able to:

o Identify shorted compressor winding
o Identify open compressor winding
o Determine grounded compressor winding.
o Observe safety precautions in testing compressor winding.

Equipment: - 1 unit
o Multi meter 1 unit
o compressor
- 1 pc
Materials:
o rag - 1 pc
1 pc
Tools: 1 pc
o Phillips screw driver
o Flat screw driver 1 pc
o Long nose pliers
o Lineman’s Pliers - 1 pair
o Diagonal cutting pliers - 1 pc

Personal Protective Equipment:
o Gloves
o Goggles

TESDA-GOTEVOT 50
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Operation Sheet 7

Procedures:

6. Unplug the unit

7. Disconnect the wiring connection of
compressor motor.

8. Set the multimeter to Rx1. Calibrate 51
the multimeter by adjusting the 0-ohm
adjust knob while the leads are
shorted.

9. Record the resistance reading
obtained from the different terminals.
Using the formula:
SR = CR + CS
13Ω = 5Ω + 8Ω
13Ω = 13Ω, therefore compressor
motor winding is good.
Note: If the resistance reading did not
conform to the formula, compressor
motor winding is defective.

10. Set the ohmmeter to Rx10, 000.

TESDA-GOTEVOT
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Operation Sheet 7

Calibrate the meter to zero and place
the test prod to common terminal and
compressor body.

Note: If the pointer deflects, the
compressor is grounded. If the pointer
did not deflect, the compressor winding
is not grounded (good).

11. Observe the following data of winding
resistance to indicate possible
compressor troubles.

Troubles Test Point Meter Indicator
infinity
Open Winding Terminals 1 & 2 and 1 &3
(R x 1) Terminals 1 & 2 and 1 &3 0 ohm reading
With deflection or continuity
Shorted Winding Terminals to casing
(R x 1)

Grounded Winding
(R x 10k)

12. Have your instructor check your work.

13. Perform housekeeping.

TESDA-GOTEVOT 52
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Job Sheet 2

Replacing Compressor Motor (Hermetic)

Objectives: At the end of this activity, the learner/trainee should be able to:

o Replace compressor motor of window-type air conditioning unit
o Follow safety practices in connecting compressor motor.

Equipment: - 1 unit
o Refrigerator Unit/Air-conditioning unit - 1 unit
o Set of system analyzer -
o Recovery/recycling machine -
o Torch set
- 1 pc
Materials: - 2 pcs
o Rug - 1 set
o Silver alloy brazing rod -
o Filter drier with sweat fittings -
o Sand cloth
o Silver brazing flux - 1 pc
- 1 pc
Tools: - 1 pc
o Tubing cutter - 1 set
o Striker - 1 pc
o Refrigeration ratchet wrench - 1 pc
o Combination open end, box end wrench
o Diagonal cutting pliers - 1 pair
o Shop towels - 1 pc
-
Personal Protective Equipment:
o Gloves
o Goggles
o Safety glasses

TESDA-GOTEVOT 53
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Job Sheet 2

1. Wear appropriate PPE

2. Check that the refrigerator is
disconnected from electrical power.
Caution: Make sure that the unit
has no pressure either
refrigerant or nitrogen.

3. Use sand cloth and polish the liquid
line prior to cutting

4. Disconnect electrical components
from the compressor.

5. Remove the compressor motor.

6. Install the new compressor.

Note: Make sure to clean the
system thoroughly before
connecting the new compressor.

7. Replace hold down bolts and tighten 54

TESDA-GOTEVOT
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Job Sheet 2

to secure the new installed
compressor.

8. Reconnect the electrical connections
of the new compressor motor.

9. Ask your instructor to check your
work.

10. Perform housekeeping

TESDA-GOTEVOT 55
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 7

Compressor Motor used in Package Air
Conditioning Unit and Commercial Refrigeration
Equipment

The function of the compressor in the refrigeration system is to draw low-pressure, low
temperature gas refrigerant into its cylinder; to compress it into a high pressure, high
temperature gas; and to discharge the refrigerant in this state to the condenser, through a
discharge valve.

Compressors are generally classified as: open type, semi hermetic, and hermetic.

Open Drive Compressor

An open drive compressor is bolted
together. Its crankshaft extends outside the
crankcase. The crankshaft is driven by a
pulley and belt or it can be driven directly by
an electric motor.

Semi-Hermetic Compressor

The motor and compressor of the
serviceable semi-hermetic compressor are
enclosed in a common housing. Usually the
cylinder head, end plates, and bottom plate
can be removed for servicing the internal
mechanism.

Hermetic Compressor

The hermetic compressor and motor
are sealed within a welded steel shell. The
shell cannot be removed for service in the
field.

TESDA-GOTEVOT 56
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 7

Compressors are further classified into four types according to the action of their
mechanical parts: reciprocating, rotary, centrifugal and screw type.

Reciprocating Compressor:

The reciprocating compressor has a piston that moves up and down or back and forth
in a cylinder. The vaporized refrigerant is drawn into the cylinder. The vaporized refrigerant is
drawn into the cylinder through an intake valve on down stroke of the piston. As the piston
completes its up stroke, the gaseous refrigerant is compressed to a specific pressure; at this
point, the discharge valve opens, and the compressed refrigerant is forced into the
condenser.

A. The low density vapor is B. The low density vapor is
drawn into the cylinder. compressed to be
converted into high
pressure vapor.

C. High pressure vapor is being D. High pressure vapor is being
released through discharge released through discharge
valve valve

TESDA-GOTEVOT 57
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 7

There are two types of rotary compressor: the stationary blade type and the rotating
blade type:

A. Intake begins. Suction gas B. Shaft continues to turn.
enters. Compression More suction gas enters
begins cylinder. Compression
continues.

C. Intake and compression D. Compression completed.
nearing end Both intake and
compression about to start

In the stationary blade rotary compressor, a roller is mounted off center on a shaft that
is in the center of the cylinder. The spring-loaded stationary blade moves in and out of the
cylinder but does not rotate with the roller. As vapor rushes into the cylinder through an
intake valve, it is trapped between the roller, the blade and the cylinder wall. As the roller
continues to turn, a larger space becomes available on the intake side of the roller and the
blade and this place is also filled with vapor. The roller keeps turning, and more vapor enters
until the blade is pushed completely out of the cylinder. As the high side of the roller passes
the blade, the gas that is trapped in the cylinder is compressed into smaller and smaller

TESDA-GOTEVOT 58
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 7

space until it reaches a specific pressure, where upon the discharge valve opens and
compressed gas is pushed into the condenser.

A. Vanes slide in and B. Suction gas entering
out trapping then the cylinder
compressing gas

The rotating blade rotary compressor has its roller centered on a shaft that is eccentric
to the center of the cylinder. As a rule, two spring loaded roller blades, mounted 180° apart,
sweep the sides of the cylinder. As the roller rotates, vapor rushes into the cylinder through
the intake port and is trapped in a space between the cylinder wall, the blade, and the point
of contact between the roller and the cylinder. The vapor is compressed as the next blade
passes the contact point and the vapor space becomes smaller and smaller. When the vapor
has been compressed, it exits from exhaust port to condenser.

TESDA-GOTEVOT 59
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 7

Centrifugal Compressor
Centrifugal compressors are used successfully in large refrigeration system. This type of
compressor, the vapor, as it is moved rapidly in circular path, moves outward. This action is
called centrifugal force.
The vapor is fed into housing near the center of the compressor. A disk with radial blade
(impellers) spins rapidly in this housing forcing vapor against outer diameter.
The centrifugal compressor has the advantage of simplicity. There are no valves or pistons
and cylinders. The only wearing part is the main bearing.

Screw Compressor

The screw compressor uses a pair of special helical rotors. They trap; and compress
air as they revolve in an accurately machined compressor cylinder.

The two rotors are not the same shape. One is male, the other female. The male rotor
is driven by the motor. It has four lobes. The female rotor mashes with and is driven by the
male rotor. It has six interlobe spaces. The cylinder encloses both rotors.

TESDA-GOTEVOT 60
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 7

In operation, the refrigerant low pressure vapor is drawn in, enters at one end of the
compressor and is discharged (compressed vapor) at the opposite end.

TESDA-GOTEVOT 61
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 8

Open Drive Compressor

Open drive compressors are manufactured in two styles: belt drive and direct drive.
Any compressor with drive on the outside of the casing has to have a shaft seal to keep the
refrigerant from escaping to the atmosphere.

Belt-Drive Compressor

Pulley-and-belt drives utilize pulleys,
or sheaves, connected by a continuous
belted loop. A belt drive always has at least
two pulleys. The driver pulley is connected to
the motor shaft, and one or more driven
pulleys connect to the load shaft. These
pulleys are coupled by a belt that transfers
the power from the driver pulley to the driven
pulley, causing rotation. About a third of all
motor transmissions use belts and pulleys.

Low cost and variable speed
capabilities are two advantages of belt and
pulley drives. On the other hand, belt pulley
systems are generally less efficient than
direct drives. The reason for this is belt
slippage. Drive efficiency diminishes rapidly
as the belt becomes worn or loose during
normal operation. This is why maintenance
requirements for this type of system are
extremely high.

The belt drive compressor was first
type of compressor and is still used to some
extent. With the belt-drive unit the motor and
its shaft are parallel with the compressor’s
shaft.

TESDA-GOTEVOT 62
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 8

Direct-Drive Compressor

Direct drives connect only to motors
and driven equipment that run at the same
speed. Direct drives allow very little loss of
power. They are generally considered to be
the most efficient drives available.

The shaft of the motor and the shaft of
the load are connected to the drive by means
of a coupling. Instead of using a solid
connection, many direct couplings have a
flexible quality which helps protect the motor
bearings from wear caused by misalignment
of the shafts. They also protect the motor
bearings from vibration developed by the
equipment to which it is connected. The two
shafts have to be in very good alignment to
run correctly.

Maintenance requirements for the
direct coupling itself are generally low unless
the coupling is not large or strong enough or
the motor and load are misaligned.

TESDA-GOTEVOT 63
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Job Sheet 3

Replace Compressor Motor (Open-Drive)

Objectives: At the end of this activity, the learner/trainee should be able to:
o change a hermetic compressor in a refrigeration/ air conditioning

system
o recover refrigerant charge
o perform leak test, evacuate and charge the system with new

compressor

Materials, Tools and Equipment:

Materials: - 1 pc
o Solenoid Valve - 1 cylinder
o Refrigerant R22
-
Tools -
o Tube cutter -
o Tube reamer - 1 set
o Refrigeration rachet - 1 set
o Wrench
o Flaring tools - 1 unit
- 1 unit
Instrument - 1 unit
o Multi-tester
o Gauge manifold - 1 unit
o Leak detector - 1 unit
- 1 unit
Equipment - 1 set
o Recovery machine
o Vacuum pump
o Oxyacetylene Outfit
o PPE

- Item is optional-

Introduction:
.
Compressor motor is the heart of a refrigeration system. It forces the refrigerant inside

the piping to circulate in the system.
Replacing the compressor motors requires a systematic procedure. The prescribe way

of replacing the compressor motor is discussed below.

Procedure:
Make sure that before you perform this activity, you are wearing appropriate personal

protective equipment.

TESDA-GOTEVOT 64
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Job Sheet 3

1. Remove the refrigerant from the
system.

2. Turn off and lockout the power,
remove the wiring from the
compressor terminals and mark each
wire.

TESDA-GOTEVOT 65
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Job Sheet 3

3. Remove the compressor hold down
nuts in bolts.

4. Remove v-belt

3. Remove suction line and discharge
line using adjustable wrench.

TESDA-GOTEVOT 66
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Job Sheet 3

4. Close the end of the tube using
masking tape.

5. Remove the compressor from the
appliance in frame and set it aside.

6. Mount new compressor as shown.
Note: Replace the compressor as
fast as possible so as not to replace
the liquid line drier.

7. Restore and align the v- belt

TESDA-GOTEVOT 67
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Job Sheet 3

8. Fasten suction line and discharge
line.

9. Pressurize the system using nitrogen
and test for leaks.

10. Evacuate the system

TESDA-GOTEVOT 68
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Job Sheet 3

11. Restore the electrical connection
12. Charge the system

13. Run the unit and observe its
operation.

14. Have your job check by your
instructor

15. Perform proper housekeeping
Evaluation:

While performing the activity it is important for you to assess your performance
following the criteria below:

 Refrigerant are removed before taking out the compressor
 Compressor and drive motor is fastened tightly to the bracket
 Electrical wirings are restored to original connection
 Belt is aligned correctly
 System is restored in to normal operation

TESDA-GOTEVOT 69
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 9

Troubleshooting Chart: Mechanical Trouble

Observable Symptoms:
 Low cooling effect
 Frosting evaporator

Start

Check if there are restrictions Restricted evaporating unit may cause
in the air flow in the evaporator refrigeration and air conditioning to have
low cooling effect because there is no
unit complete evaporation of refrigerant.

Is there any Clean evaporator unit 1
restriction? or remove any

restriction to the air
flow

1 Check evaporator fan Defective evaporator fan will have the
motor same effect with restricted air flow in the
condensing unit
Maintain/ Repair/
Replace evaporator 2

motor

Does evaporator If the air flow is not restricted Recover/ recycle
fan motor require and the fan motor is Refrigerant
functioning properly, the
maintenance/ most probable cause of the Change Filter
repair/ system not cooling is a
contaminated refrigerant. Evacuate the system
replacement?

2 Test run the unit

Did the unit
function
properly?

Re-charge the system

2

Stop

TESDA-GOTEVOT 70
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 9

Trouble: Compressor runs continuously (air conditioner)
Observable Symptoms:

 No cooling effect on the evaporator
 High pressure on the high side of the unit

Start

Check if the condensing unit is Restricted condensing unit may cause
full of air restriction refrigeration and air conditioning not to
have cooling effect because there is no
Is it full of air complete condensation of refrigerant.
restriction?
Clean condensing unit 1
or remove any

restriction to the air
flow

Check if the condenser fan Maintain/ repair/ 2
replace condenser fan
1 motor requires maintenance/
motor
repair/ replacement
Defective condenser motor
Does the motor will have the same effect
require with restricted air flow in the
condensing unit
maintenance /
repair/

replacement?

Recover/ recycle
Refrigerant

Test run the unit 2 If the air flow is not restricted
and the fan motor is
functioning properly, the Change Filter
most probable cause of the
system not cooling is a
contaminated refrigerant.

Did the unit Evacuate the system
function
properly?

Re-charge the system

2

Stop

TESDA-GOTEVOT 71
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 9

Trouble: Compressor operate in short cycle
Observable Symptoms:

 Low cooling effect
 Frosting evaporator

Start

Check if there are restrictions Restricted evaporating unit may cause
in the air flow in the evaporator refrigeration and air conditioning to have
low cooling effect because there is no
unit complete evaporation of refrigerant.

Is there any Clean evaporator unit 1
restriction? or remove any

restriction to the air
flow

1 Check evaporator fan Defective evaporator fan will have the
motor same effect with restricted air flow in the
condensing unit
Maintain/ Repair/
Replace evaporator 2

motor

Does evaporator If the air flow is not restricted Recover/ recycle
fan motor require and the fan motor is Refrigerant
functioning properly, the
maintenance/ most probable cause of the Change Filter
repair/ system not cooling is a
contaminated refrigerant.
replacement?

2 Test run the unit

Did the unit Evacuate the system
function Re-charge the system
properly?
2

Stop

TESDA-GOTEVOT 72
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 9

Trouble: Compressor runs continuously

Observable Symptoms:

 Low cooling effect
 Low pressure on the low side of the unit

Start

Check if there are restrictions Restricted evaporating unit may cause
in the air flow in the evaporator refrigeration and air conditioning to have
low cooling effect because there is no
unit complete evaporation of refrigerant.

Is there any Clean evaporator unit 1
restriction? or remove any

restriction to the air
flow

1 Check evaporator fan Defective evaporator fan will have the
motor same effect with restricted air flow in the
condensing unit
Maintain/ Repair/
Replace evaporator 2

motor

Does evaporator
fan motor require

maintenance/
repair/

replacement?

Leak in the system may also
cause the pressure to drop.

3 Leak test the unit Repair Leak 2

Is there a 3
leak?
Did the unit
2 function
properly?
Replace metering Test run the unit
device

Defective metering device may prevent Stop
refrigerant to build required pressure.
73
TESDA-GOTEVOT
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 9

Trouble: Compressor runs continuously
Observable Symptoms:

 Low cooling effect in the room temperature
 The running current of the current is normal

Start

Adjust the thermostat control Thermostat is a device used in controlling
of the unit to the coolest level the adjustment of temperature setting of
the unit. This adjustment is done to set
the unit to coolest setting.

Test-run the unit while
observing any charge in the

1 room temperature

Is the change Room insulation helps in Redesign air
in the room maintaining the cold air in the conditioning
temperature room. system for the
sufficient?
Check room room
Stop installation

Is the room
properly
insulated?

Add room 1
insulation

1

TESDA-GOTEVOT 74
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 9

Trouble: Compressor runs continuously
Observable Symptoms:

 Normal cooling effect
 Normal current

Start

Adjust the thermostat control
of the unit to the warmest
cool setting

Test-run the unit while
observing any charge in the

1 room temperature

Did the The thermostat should be
compressor placed where it can sense
the return air
turn off?
Check
positioning of

thermostat

Stop Is the sensing Replace
element in thermostat
proper
position? 1

Check positioning
of sensing
element

1

TESDA-GOTEVOT 75
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Assignment Sheet 4

Troubleshooting PACU/CRE: Mechanical Trouble

Objectives: At the end of this activity, the learner/trainee should be able to:
o Apply different testing method in determining the defects of

PACU and CRE
o State the recommended action to repair the defective unit

Direction: Troubleshoot a package-type air conditioning unit and commercial refrigeration
equipment. Note your findings using the form below.

Station number: PACU CRE
Type:
Temperature:
High pressure side:
Low pressure side:
Full load current:
Root causes:

Recommended action

Station number: PACU CRE
Type:
Temperature:
High pressure side:
Low pressure side:
Full load current:
Root causes:

Recommended action

TESDA-GOTEVOT 76
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 10

Troubleshooting Unit When Compressor Fails to
Start

The most noticeable symptoms of a compressor not running are when the system
fails. Not functioning compressor can be detected and verified by using a voltmeter, ac clamp
ammeter and ohmmeter.

The voltmeter will be used to detect the presence of electromotive force (voltage) in
the terminal of the compressor. Lack of voltage means, the electrical path from the supply to
the compressor is open this is the reason why the compressor is not running. Low voltage
may also cause for the compressor not to run. Normal voltage means that the compressor
motor would function if it will draw current from the system.

The ammeter will be used to detect the current being drawn by compressor. The
reading will be compared to the compressor motor’s FLA and LRA. Lower current reading
means that the compressor is not drawing current from the source which is the reason for it
not to function. High current being drawn by the compressor means it is overload, which may
cause some protector to break the circuit and cut the supply going to the compressor.
Normal current means that the compressor motor is dissipating enough power to drive the
system.

Ohmmeter will be used to check and verify the condition of the compressor motor coil
out circuit. The continuity of the coil is checked because some technicians made mistakes in
jumping into conclusion that because the compressor does not draw current the compressor
motor coil is defective. There are cases wherein the reason why the compressor does not
draw current is because of loose connections in the compressor terminal. This mistake can
be eliminated by verifying the integrity of the compressor motor out circuit.

Three Major Probable Causes for a Compressor Motor Not to Function

There are three major probable causes for a compressor motor not to function; (1) the
electrical line that will supply the power for the motor is open; (2) the compressor motor is
defective or overloaded and; (3) the power supply is below than the required power of the
unit.

Among the three major probable causes, the first one is the trickiest to troubleshoot
because you need to trace the signal from the load side (terminals of the compressor motor)
to the line side (terminals of circuit protector). You need to find out where the signal stops
due to a defective component or protector design.

TESDA-GOTEVOT 77
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 10

Take the diagram above. The highlighted part is the compressor circuit. As you can
see, the signal path from the compressor terminal going to the source terminal passes
through different devices. If your going to trace the signal path you can see that from
terminal C of the compressor, the signal passes through the overload protection, going to
compressor switch (terminal 1 and 1A), then dual pressure control (terminal 3 to 1),
thermostat (terminal L and C), then main power switch (terminal 2B- 1B), then going through
the MCB and finally connected to L1. On the other hand the electrical path for S and R
terminal of the compressor passes through the current relay (Terminal S and M going to
terminal 1), then main power switch (terminal 2 A and 1) finally connected to L2.

To trace the signal from this circuit, you need test the presence of voltage in the
terminal of compressor, if there is you can assume the compressor it self is defective (see
operation sheet in testing compressor in the learning element compressor motor for more
details), if there is low voltage or non at all, you need to trace back the signal path from the
compressor to the supply line terminal.

The second major probable cause of trouble is simpler to troubleshoot. A defective
compressor motor can be caused by an open motor coil or shorted motor coil. Overloaded
compressor may have similar symptoms with shorted motor coil when tested in operation.
The open coil has the symptom of not drawing current from the source when checked with an

TESDA-GOTEVOT 78
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 10

ac clamp ammeter. To finally verify that the cause of trouble is really an open coil, continuity
of the coil must be checked using an ohm meter (see operation sheet in testing compressor
in the learning element compressor motor for more details).

The shorted coil or overloaded compressor however is a little bit trickier. The symptom
of these troubles is drawing excessive current from the supply source (more than 600% of
FLA rating) and probably tripping-off the protective device of the system when the unit is
tested for operation (power-on testing). To identify whether the compressor motor coil is
shorted, check the resistance of the coil. Although the normal resistance of the coil is very
low, shorted coil is still noticeable. Overloaded compressor however will have a non-shorted
coil but draws excessive current when energized. It may happen due to overcharging of
refrigerant, liquid slugging (liquid refrigerant returns to compressor during off cycle), air in the
system, changes in pressure in the low side and high side or partial stuck-up of crankshaft
due to lack of lubricant. This trouble basically is not compressor trouble, but the load and
effect falls in the compressor. Necessary corrective actions should be done (refer to the
learning element repair and retrofit for more details).

The third major probable cause is low voltage supply. This can be checked by using a
volt meter. The voltage supplied to the unit should not be less than or greater than 10% of
power rating of the unit (see nameplate of the unit). This trouble may be caused by a blown
fuse in supply line or trouble in the local power distribution.

Low voltage supply may cause severe damage to compressor due excessive current
drawn by the motor winding to compensate the power required by the unit therefore
protection device is essential to prevent the motor from overheating.

TESDA-GOTEVOT 79
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 11

Troubleshooting Chart Electrical Troubles

Trouble: The unit does not start

Observable Symptoms:
 The circuit breaker keeps tripping off

Start

You can check the load
side for short circuit by
using an ohmmeter.

Check the load side of 3
the circuit breaker for

short circuit

Locate the short Reset the circuit
in the circuit breaker,

A good technique in 1 Test the unit for
locating short circuit is operation
by isolation. You
Is the Yes isolate the components
circuit which dissipate big
shorted? amount power then
measure their
No resistance. Some a
short circuit can be

caused by faulty wiring.

No Did the Yes
unit

Defective circuit breaker function?
may trip repeatedly even
Replace circuit though there is no short in Does it have 2 Stop
breaker the circuit the same

1 No symptom as
before?
Refer to other
troubleshooting guide Yes

3
2

TESDA-GOTEVOT 80
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 11

Trouble: The unit does not start

Observable Symptoms:
 Supply in the load side of the circuit breaker is normal
 Evaporator fan circuit, ok
 Condenser fan circuit, ok

Start Tracing back circuit can be done 2
visually or by measuring the
Check power in the continuity of the line
terminal of the
Does the supply No Trace-back circuit for
compressor, to verify if reach the loose wiring.
the signal reaches
compressor terminal of the
compressor?

Replace compressor Yes Restore Is there a
motor connection loose wiring?
If signal is present in the
terminal of the compressor, 1 Check controls and
therefore it is safe to assume protections for defects
that the compressor is defective
or troubles
Test the unit for Control and protection contacts
operation 1 are connected in series with the Repair/replace control
or protection
Did the Yes power line going to the
unit compressor. Defects from these 1
devices can cause the
function? compressor not to run

No Stop

Does it have 2
the same

symptom as
before?

No

Refer to other
troubleshooting guide

TESDA-GOTEVOT 81
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Information Sheet 11

Trouble: Compressor does not start (single phase motor)

Observable Symptoms: Open or loose connection in
 Compressor hums
 Supply is normal the start line may cause the
 High current
2 compressor not to start
Start because it will cut the current

going to the start winding.

Check current 3 Check loose or open
relay/potential connection at the start
Defective relay may cause line of the compressor Overload or stuck-up
relay compressor may cause the
compressor to hum Is there a compressor to hum and
Is the loose or open draws a large amount of
relay because it will cut the connection? No current.
defective?
No current flowing to start
winding.

Yes Is there a No Yes Check motor
Change Relay capacitor? compressor for
Restore loose open starting coil
connection open circuit or mechanical

stuck up

Yes 1
1 Repair/ replace

compressor motor

Check 1
capacitor
Defective capacitor may cause Refer to other
Is the compressor to hum because it troubleshooting guide
capacitor 2 will not be able to change the No
defective? phase angle of the current
flowing in the start winding which Does it have
Replace may prevent the rotor from the same
Capacitor revolving
symptom as
1 before?

Test unit for No
operation
Did the unit
work Yes Yes
3
properly?

Stop

TESDA-GOTEVOT 82
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Assignment Sheet 5

Troubleshooting PACU/CRE: Electrical Troubles

Objectives: At the end of this activity, the learner/trainee should be able to:
o Apply different testing method in determining the defects of

PACU and CRE
o State the recommended action to repair the defective unit

Direction: Troubleshoot a package-type air conditioning unit and commercial refrigeration
equipment. Note your findings using the form below.

Station number: PACU CRE
Type:
Full load current:
Symptoms

Root causes:

Recommended action

Station number: PACU CRE
Type:
Full load current:
Symptoms

Root causes:

Recommended action

TESDA-GOTEVOT 83
Troubleshooting Package Type Air Conditioning Unit and Commercial Refrigeration Equipment
Version 2007 -1.0

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Commercial Refrigeration Equipment

Introduction Troubleshooting Package-type Air Page
Conditioning Unit/ Commercial 1 of 29
Refrigeration Equipment

Introduction:

Welcome to the Module on “Troubleshooting Package-type Air
Conditioning Units/Commercial Refrigeration Equipment”. This module covers
the required knowledge, skills and attitude of the unit of competency “Troubleshoot
Package-type Air Conditioning Units/Commercial Refrigeration Equipment” in
a Package-type Air Conditioning Units/Commercial Refrigeration Equipment
Servicing NC II Course.

Summary of Learning Outcomes:
On completion of this module you should be able to:

 Troubleshoot electrical trouble of PACU/CRE
 Troubleshoot mechanical trouble of PACU/CRE

Assessment Criteria

To be able to verify that you are competent enough in this module you must be
able to demonstrate the criteria listed below while performing tube processing
activities and installing piping system for PACU/CRE.

 Locating cause of electrical trouble is done following prescribed procedure
 Electrical components are tested in accordance with prescribed procedure
 Defective electrical parts are repaired/replaced in accordance with prescribed

procedure
 Locating cause of mechanical trouble is done following prescribed procedure
 Mechanical components are tested in accordance with prescribed procedure
 Defective Mechanical parts are repaired/replaced in accordance with

prescribed procedure
 Unit is tested following prescribed procedure

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Commercial Refrigeration Equipment

Introduction Troubleshooting Package-type Air Page
Conditioning Unit/ Commercial 2 of 29
Refrigeration Equipment

Conditions:

The trainee must be provided with the following:

Equipment Tools
 Oxyacetylene equipment
 Electric drill  Hacksaw
 Packages air conditioning unit  Push-pull rule
 Flat file
Supplies and Materials  Half round file
 Lubricant  Tube cutter
 Replacement components  Flaring tools
 Refrigerant  Swaging tools
 Polyethylene tape  Ball peen hammer
 Insulator  Swaging punch
 Marker/ pen, chalk  Wrench
 Bond paper  Pliers
 Copper tubing soft drawn  Screw drivers
 Copper tubing hard drawn  Nut driver
 Rand sand paper
 Rag Learning Materials
 Silver rods  LE on tube processes
 Silver rod, eutectic type
 Flux  LE in tools equipment used in
 Wet cloth RAC servicing

 T copper tubes 3/8  LE in Electrical Circuit
Protection
 Copper tube 3/8
 LE in Recovering and
 Wires Recycling
 Electrical tapes
 LE in charging refrigeration
Personal Protective Equipment System

 Helmet /hardhat  LE in Compressor Motor
 Goggles  LE in Metering Devices
 Gloves  LE in Refrigeration
 Gas Mask
 Working clothes/ jacket/apron Accessories
 Safety shoes  Learning Module in Servicing

and Maintaining PACU/CRE

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Commercial Refrigeration Equipment

Introduction Troubleshooting Package-type Air Page
Conditioning Unit/ Commercial 3 of 29
Refrigeration Equipment

Reference Materials:

 Althouse A. D., Turnquist C. H., Bracciano A. F.MODERN REFRIGERATION
AND AIR CONDITIONING. 1992. The Goodheart-Willcox Company, Inc.

 Institute of Integrated Electrical Engineers. PHILIPPINE ELECTRICAL
CODE, Part 1, 2000 Edition. June 2002. Bookman Inc.

 Jones L., Morse O. SHEET METAL BASICS. 1983. Mid-America Vocational
Curriculum Consortium, Inc.

 CODE OF PRACTICE FOR REFRIGERATION AND AIR CONDITIONING
(Philippine Setting. June 2004. Department of Environment and Natural
Resources (DENR)

Prerequisites:

To complete this module you must have the competency in doing different
bench work activities and maintaining tools and equipment, performing basic
electrical activities. It is also required that you have the competence in performing
good housekeeping and safety practices. If you still lack these competencies,
meet with your trainer/facilitator to determine what method you will use to gain
the said skill. One option is to complete the information and practice activities in
the following modules:

 Performing Basic Bench Work Activities
 Performing Mensuration and Calculation
 Performing Good Housekeeping and Safety Practices
 Performing Basic Electrical Works

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Commercial Refrigeration Equipment

Introduction Troubleshooting Package-type Air Page
Conditioning Unit/ Commercial 4 of 29
Refrigeration Equipment

About this Competency Based Learning Material

This Competency Based Learning Material is composed of a learning guide
and Resource-pack. The Learning guide will help the learner in achieving the
competence required in the competency standard for installing package-type air
conditioning unit/ commercial refrigeration equipment piping system.

In going through the Learning Guide, you must follow the “Learning Activity
Sheet”. This Learning Activity Sheet will guide you through different “Instruction
Sheets” (located at different resource-packs) that will assist you in performing
different learning activities towards the attainment of the learning outcome.

The instruction sheet may be in the form of:

 Information Sheet - This will provide you with information (concepts,
principles and other relevant information)
needed in performing certain activities.

 Operation Sheet - This will guide you in performing single task,
operation or process in a job.

 Job Sheet - This is designed to guide you how to do a job
that will contribute to the attainment of the
learning outcome.

 Assignment Sheet - The assignment sheet is a guide used to
enhance (follow-up) what you have learned in
the information sheet, operation sheet or job
sheet.

 Worksheet - Worksheets are the different forms that you
need to fill-up in certain activities that you
performed.

How to Use this Competency-Based Learning Material

This learning material is designed to guide you in learning at your own pace.
To start with, talk with your trainer and agree on how you will both organize the
training for this module. Most probably your trainer will also be your supervisor or
manager. He/she is there to support you and guide you the correct way to do
things. From time to time you will be required to practice and demonstrate the
skills that you’ve learned from this module and you will be requiring some
assistance from your trainer (as instructed in the learning material).

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Commercial Refrigeration Equipment

Introduction Troubleshooting Package-type Air Page
Conditioning Unit/ Commercial 5 of 29
Refrigeration Equipment

To proceed with the learning session you just have go through the Learning
Activity Sheet where in you will follow series of learning instructions towards
attaining the learning outcome.

For example:

The learning instruction states that you are to perform Reading
Activity 1. The instruction sheet needed is Information Sheet 1 with the title
Operation of Window-type Air-conditioning Unit located at page 7 of this
learning material. Below the learning instruction is a short description of the
instruction sheet. Special instructions which you may need to follow while
doing this activity may also be found in this section, if there are any.

Learning Instruction sheet Title of the Page where the
Instruction type and number instruction instruction sheet is

sheet located

Description of the content of
instruction sheet and sometimes
special instructions that you need to
follow while performing this learning

activity

This procedure should be repeatedly done until you have completed all the
learning elements in this Competency-Based Learning Module or until such time
that you are ready to take the final assessment for this module. You may skip
some learning activities if you can demonstrate that you are competent
enough on the said task/s.

At the end part of this module is a Learner’s Diary. Use this diary to record
important dates, jobs undertaken and other workplace events that may provide
further details to your trainer or assessor. A Record of Achievement will be
provided to you by your trainer for you to accomplish once you complete the
module.

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Commercial Refrigeration Equipment

Introduction Troubleshooting Package-type Air Page
Conditioning Unit/ Commercial 6 of 29
Refrigeration Equipment

Upon completion of this module, study the evidence plan at the end of the last
learning element of this module then ask your instructor to assess you. You will
be given a certificate of completion as proof that you met the standard
requirements (knowledge, skills and attitude) for this module. The assessment
could be made in different methods, as prescribed in the competency standards.

If you have questions, don’t hesitate to ask your instructors for
assistance. Your instructor will always be available to assist you during the
training.

Recognition of Prior Learning (RPL)

You may already have some or most of the knowledge and skills covered in
this module because you have:

 been working for some time
 already completed training in this area.

If you can demonstrate to your trainer that you are competent in particular
skill, talk to him/her about having them formally recognized so you would not
have to undergo the same training again. If you have a qualification or Certificate
of Competency from previous trainings, show it to your trainer. If the skills you
acquired are still current and relevant to this module, they may become part of
the evidence you can present for RPL. If you are not sure about the level of your
skills, discuss this with your trainer.

Symbols

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Commercial Refrigeration Equipment

Introduction Troubleshooting Package-type Air Page
Conditioning Unit/ Commercial 7 of 29
Refrigeration Equipment

These symbols are located in the left margin of the module. It illustrates action
which should be taken or resources to be used at the particular stage in this module.

Learning Optional Activity
Outcome

Resources Practice

Reading Activity Self Check

Use Computer Answer Key

View Video Competency
Assessment
Listen to Audio
Tape Safety

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Learning Commercial Refrigeration Equipment
Activity
Troubleshooting Package-type Air Page
1 Conditioning Unit/ Commercial 8 of 29
Refrigeration Equipment

Troubleshoot Electrical Trouble of
PACU/CRE

Assessment Criteria:

The learning outcome stated above is attained if you
can demonstrate the following:

 Locating cause of electrical trouble is done following
prescribed procedure

 Electrical components are tested in accordance with
prescribed procedure

 Defective electrical parts are repaired/replaced in
accordance with prescribed procedure

 Unit is tested following prescribed procedure

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Learning Commercial Refrigeration Equipment
Activity
Troubleshooting Package-type Air Page
1 Conditioning Unit/ Commercial 9 of 29
Refrigeration Equipment

Reading Activity 1

Read: Information Sheet 1 of Copper Tubes different
the Learning Element

for tubing, piping

and fittings (LE 0001)
o This is an informative sheet that discusses

characteristics of copper tubes.

Reading Activity 2

Read: Information Sheet 2 of Other Tubes and Pipes used
the Learning Element in Refrigeration System
for tubing, piping
and fittings (LE 0001)

o This is an informative sheet that discusses different
characteristics of other types of tubes and pipes used in
refrigeration system

Self-Check 1 p.14

Do: Self-Check 1 on this Learning guide

o This is to self-evaluate what you have learned about the
different types of tubes and pipes used in refrigeration system

o After answering the questionnaire, you may check your answer
with the answer key located at the back part of this learning
material. You need to get at least 80% correct answer on the
self-check before proceeding to the next learning activity.

Practice Activity 1

Perform: Operation Sheet 1 on Cutting Tube Using Tube
Learning element for Cutter
tube processes
(LE 0003)

o This activity aims to guide you in cutting soft drawn copper
using tube cutter.

o If your not familiar with the cutting tool yet, supplemental
information about cutting tool can be found at the learning
element for tools and equipment used in refrigeration and air
conditioning servicing (LE 0002).

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Learning Commercial Refrigeration Equipment
Activity
Troubleshooting Package-type Air Page
1 Conditioning Unit/ Commercial 10 of 29
Refrigeration Equipment

Practice Activity 2

Perform: Operation Sheet 2 on Cutting Tube Using
Learning element for Hacksaw
tube processes
(LE 0003)

o This activity aims to guide you in cutting hard drawn copper
using tube cutter.

Practice Activity 3 p.15

Perform: Assignment Sheet 1 Cutting Hard Drawn Tubes
on this Learning
Guide

o This activity aims to enhance your skill in cutting hard drawn
copper tube by either using a tube cutter or hacksaw and to
prepare materials to be used in practices and the actual
installation of the piping system for PACU/CRE.

Practice Activity 4

Perform: Operation Sheet 3 on Annealing Copper Tubes
Learning element for
tube processes
(LE 0003)

o This activity aims to guide you in the process of annealing hard
drawn and old stock copper tubes

o Before you can do this activity, you need to know first how to
use oxyacetylene equipment. If you lack the knowledge and
skills in using oxyacetylene equipment, supplemental
information and activity can be found at the learning element for
tool and equipment used in refrigeration and air conditioning
servicing (LE 0002)

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Learning Commercial Refrigeration Equipment
Activity
Troubleshooting Package-type Air Page
1 Conditioning Unit/ Commercial 11 of 29
Refrigeration Equipment

Practice Activity 5 p.16

Perform: Assignment Sheet 2 Annealing Copper Tubes
on this Learning
guide

o This activity aims to enhance your skill in performing annealing
of copper tubes and to prepare materials to be used in practices
and the actual installation of the piping system for PACU/CRE

Practice Activity 6

Perform: Operation Sheet 4 on Tube Bending
Learning element for
tube processes
(LE 0003)

o This activity aims to guide you in bending soft drawn copper
tube

Practice Activity 7

Perform: Operation Sheet 5 on Insulate Copper Tubing
Learning element
Installation of
Refrigeration Piping
System (LE 0004)

o This activity aims to guide you in insulating copper tubing

Reading Activity 3

Read: Information Sheet 3 of Refrigeration Fittings
the Learning Element
for tubing, piping
and fittings (LE 0001)

o This is an informative sheet that discusses the most common
fitting used in refrigeration and air conditioning units

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Learning Commercial Refrigeration Equipment
Activity
Troubleshooting Package-type Air Page
1 Conditioning Unit/ Commercial 12 of 29
Refrigeration Equipment

Self-Check 2 p.17

Do: Self-Check 1 on this Learning guide

o This is to self-evaluate what you have learned about the
different types of refrigeration fittings.

o After answering the questionnaire, you may check your answer
with the answer key located at the back part of this learning
material. You need to get at least 80% correct answer on the
self-check before proceeding to the next learning activity.

Practice Activity 8

Perform: Operation Sheet 5 on Flaring
Learning element for
tube processes
(LE 0003)

o This activity aims to guide you in performing copper flaring
operation.

o If you are not familiar yet with the flaring, supplemental
information about flaring tool can be found at the learning
element for tools and equipment used in refrigeration and air
conditioning servicing (LE 0002).

Practice Activity 9 p.18

Perform: Assignment Sheet 3 Preparing Flared Joints
on this Learning
guide

o This activity aims to enhance the knowledge, skill and attitude
that you have learned in flaring process. It also aims to prepare
the materials for the actual installation practice of piping system
for PACU/ CRE

Unit Troubleshoot Package-type Air Conditioning Unit/
Module
Learning Commercial Refrigeration Equipment
Activity
Troubleshooting Package-type Air Page
1 Conditioning Unit/ Commercial 13 of 29
Refrigeration Equipment

Practice Activity 10

Perform: Operation Sheet 6 on Swaging
Learning element for
tube processes
(LE 0003)

o This activity aims to guide you performing swaging soft copper
tubing.

Practice Activity 11 p.19

Perform: Assignment Sheet 4 Swaging Practices
on this Learning
guide

o This activity aims to enhance your knowledge, skills and
attitude in swaging process. It also aims to prepare the needed
materials in brazing practices.

Practice Activity 12

Perform: Operation Sheet 7 on Perform Brazing and
Learning element for Soldering
tube processes
(LE 0003)

o This activity aims to guide you performing brazing and soldering
on copper tubes.

Practice Activity 13 p.20

Perform: Assignment Sheet 5 Soldering and Brazing tube

on this Learning fittings

guide

o This activity aims to enhance your skills, knowledge and

attitude that you have learned from previous activity.

Unit Install Package-type Air Conditioning Unit/Commercial
Module
Refrigeration Equipment Piping System

Self-Check 1 Installing Package-type Air

Conditioning Unit/ Commercial Page

Refrigeration Equipment Piping 14 of 29

System

Test what you have learned about the different
types of tubes and pipes

Direction: Read the questions carefully. Write the answer on the space provided.

1. What do we call the copper tube which is already annealed?

2. What wall thickness is commonly used?

3. What happens to the working pressure of the tube if the
temperature increases?

4. What type of plastic pipe can be used for hot or cold water
source?

5. What type of metallic pipe is commonly used in food
processing and manufacturing?