Diagnostico Bus TermoKing

8/13/2019 Diagnostico Bus TermoKing

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CONVERSIONS ENGLISH TO METRIC

1 Btu = 252 Gram-calories1 Btu/Hr =.252 K cal/Hr

1 Btu/Hr-F =.453 K cal/Hr.C

1 Btu/Hr-Ft2-F = 4.88 K cal/Hr-M2-C

1 Cfm = 28.32 Liters/Minute

1 Cfm = 1.7 Cubic Meters/Hr

5/9 (F-32) = C

1 Foot =.3048 Meter

1 Square Foot =.0929 Square Meter

1 Cubic Foot =.0283 Cubic Meter

1 Gallon = 3.785 Liter1 Inch = 2.54 Centimeters

1 Square Inch = 6.452 Square

Centimeters

1 Cubic Inch = 16.39 Cubic Centimeters

1 Inch H20 = 2.54 Grams/CM2

1 Pound = 453.6 Grams

1 PSI =.07031 Kg/CM2

1 Watt = 3.413 Btu/Hr

Micron =.0000001 Meters

This Manual is published for informational purposesonly and the information so provided should not be

considered as all-inclusive or covering all contingencies.

If further information is required, Thermo King

Corporation should be consulted.

Thermo Kings warranty will not apply to any equipment

which has been so repaired or altered outside the

manufacturers plants as, in the manufacturers

judgment to effect its stability.

No warranties, express or implied, including

warranties of fitness for a particular purpose ormerchantability, or warranties arising from course

of dealing or usage of trade, are made regarding the

information, recommendations, and descriptions

contained herein. Manufacturer is not responsible

and will not be held liable in contract or in tort

(including negligence) for any special, indirect or

consequential damages, including injury or damage

caused to vehicles, contents or persons, by reason

of the installation of a Thermo King product or its

mechanical failure.


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Table of Contents

1

Safety Cautions 3

Responsible Refrigerant Handling 5

T-series Flow Diagram 6

R-series Flow Diagram 7

Diagnosing A System With an EPR Valve 8

Diagnosing A System Without an EPR Valve 9

EPR Non-Mechanical Cooling Problems 10

Conditions That Cause High Discharge Pressure 11

Conditions That Cause Low Discharge Pressure 11

Diagnosing Using The Liquid Line 11

Refrigeration System Access Tools 12-13

Compressor Service Valves 14

Gauge Manifold Installation (Standard Hose Fittings) 15-16

Gauge Manifold Installation (Low Loss Fittings) 17

Gauge Manifold Removal 18

Refrigerant Level Check 19-20

Adding Refrigerant 21

Charging An Evacuated Unit By Weight 22-23

EPR Valve Adjustment 24-27

Low Side Pump Down 28-29

Compressor Pump Down 30

Compressor Oil Pressure Check 31

Compressor Oil Level Check 32

Removing Compressor Oil 33

Adding Compressor Oil 34-35

Compressor Efficiency Test 36

Air Gap Adjustment 37

Testing For Air In System 38-39

Superheat 40-41

(Continued)

SAFETY

DIAGNOSTICS AND SERVICE TOOLS

SERVICE PROCEDURES


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Table of Contents

2

Refrigerant Leak Check Tools 43

Leak Characteristics 44

Recommended Solders and Soldering Procedures 45-46

Refrigerant Recovery 47

Recovery From A Working Unit Without an Orit 10 Valve 48

Recovery From A Working Unit With an Orit 10 Valve 49

Recovery From Non-working Unit 50

System Evacuation and Clean Up 51-52

Multiple Evacuation 52

Compressor Oil Acid Test 53

Compressor Oil Filter Kit 54

Suction Line Filter 54

Refrigerant Types and Properties 55

Temperature Pressure Relationships Chart 56-57

Bus Refrigeration Terminology 59-72

LEAK TESTING / SOLDERING / CLEAN UP

REFRIGERANT TYPES AND PROPERTIES

TEMPERATURE CHARTS

GLOSSARY


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3

Safety

DO NOT EXPOSE REFRIGERANTTO OPEN FLAME AS TOXIC FUMES

MAY BE RELEASED

CAUTION: STAY CLEAR

OF FANS AND OTHER

MOVING PARTSAJA785

CAUTION

ALL SERVICE VALVES MUST BE

BACK SEATED PRIOR TOREMOVING SERVICE PORT CAPS.

NOTE: SOME VALVES MAY NOT

HAVE A BACK SEAT.

HAZARDOUS VOLTAGE

CAN CAUSE SEVERE

INJURY OR DEATH AJA786


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4

Safety

ALWAYSWear Eye Protection

and Protective Clothing

When Handling Refrigerant

ALWAYSWear Eye and Ear

Protection When ServicingRefrigeration Units

CAUTION

Bus climate control systems are controlled by a

thermostat that may cycle the unit ON or OFF with

no prior warning. Condenser and evaporator fanswill start when the unit is cycled ON by the thermo-

stat. Do not wear loose fitting clothing or equip-

ment around operating climate control systems.

Always disconnect power to the unit before per-

forming any maintenance procedures.

AJA787


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5

Safety

Responsible Refrigerant Handling

Knowledge and Skills

Vital to Human Health

Scientific Evidence indicates that CFC refrigerantscon-

tribute to the depletion of the ozone layer and permits

an increasein the harmful ultraviolet raysthat reach the

earth.

Protecting the ozone layer through responsible refrigerant

handling is the responsibility of all refrigeration and air con-

ditioning service technicians.

Service Tools --Use the proper service tools. Gaugemanifold sets should include appropriate shutoff valves

or disconnects near the end of each service line.

Recovery Equipment -- Recovery equipment must be

used. Proper recovering, storing and recycling of refrig-

erants is an important part of all service work.

Service Procedures -- Recommended procedures

must be used to minimize refrigerant loss.

Components may be isolated by closing service valves

and performing system pump-downs.

Components unable to be isolated for service must be

repaired only after refrigerant is properly recovered.

ALWAYSHANDLE REFRIGERANT RESPONSIBLY

AND PREVENT REFRIGERANT LOSS

TO THE ATMOSPHERE.


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6

Diagnostics and Service Tools

T SERIESBUS CLIMATE CONTROL SYSTEM

AJA789

AJA788


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7


R SERIESBUS CLIMATE CONTROL SYSTEM

AJA791


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8


Diagnosing a System with a EPR Valve

SUCTIONLINE

A. COMPRESSOR SUCTION PRESSURE

Condition Low High

Frosty/Cold 1. Normal operation: Bus iscontrolling thermostat withlight load and/or at higherspeeds.

2. EPR valve set too high.3. Airflow through evap. is low.

Air filter dirty. Evaporator coil dirty.

4. EPR valve set too low: Coil frosted up.

5. Evaporator Blower Motor. Low Voltage.

ElectricalMalfunction.

Fan Blades -Damaged, Location,Direction.

1. Normal operation: Heavy load on the

evaporator2. Expansion valve malfunction:

Feeler bulb making poorcontact with suction line

Needle erodedvalvecan not control properly

Adjustment has beenincorrectly set (lowsuperheat)

Dry/Warm 1. Low refrigerant charge.2. Restriction in liquid line.3. Expansion valve malfunction:

Inlet screen plugged. Adjustment has been

incorrectly set (highsuperheat).

Feeler bulb lostcharge.

4. Too much oil in system.5. Restricted suction line.6. Airflow through condenser

coil too cold.

1. Compressor malfunction: Leaking discharge

valves. Leaking piston reeds. Worn piston/sleeve

assembly (blow-by).2. Heavy load on evaporator:

Compressor turning tooslowly.

Belts slipping. Clutch slipping.

B. COMPRESSOR DISCHARGE PRESSURE

Low High

Suction LineConditionDoes Not

Apply

1. Low refrigerant charge.2. Light load on evaporator:

Bus interiortemperature cool.

Dirty air filters. EPR set too lowcoil

frosted up. Airflow through

evaporator is low forsome reason.

3. EPR valve incorrectlyadjustedtoo high causinglow refrigerant flow.

4. Compressor speed low.5. Airflow through condenser is

cold.6. Restrictions to refrigerant

flow: Liquid line restricted Suction line blockage

1. Airflow into the condenser is lowor restricted: Dirty coil. Debris in the coi l in let .

2. Condenser fan or motorproblem: Motor running on low

speed. Motor not running

electrical malfunction. Fan blade(s) broken or

incorrectly adjusted.3. Restriction on high side of the

system: In-line service valve

partially closed.4. Non-condensables in system:

Air, ni trogen, and othergases(?).

5. Hot air entering the condensercoil.


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9


Diagnosing a System without a EPR Valve

SUCTIONLINE

A. SUCTION PRESSURE

Condition Low High

Frosty/Cold 1. Restricted airflow throughthe evaporator coil Iced up evaporator

coil Dirty evaporator

coil Plugged evaporator

filter2. Evaporator blower motor

Low voltage Electrical

malfunction

Fan bladesdamage, location,direction

1. Expansion valve malfunction: Feeler bulb making poor

contact Valve adjustmentopen

too much (lowsuperheat)

Valve needle eroded2. Overcharge of refrigerant

Dry/Warm 1. Low refrigerant charge2. Restricted drier3. Expansion valve

malfunction:Plugged screendirt, waxValve adjustmentclosedtoo much (high superheat)Internally frozenexpansion valveice frommoistureFeeler bulb lost charge

4. Overfill of compressor oil5. Restricted line in low side6. Airflow through condenser

coil too cold

1. Leaking discharge valve plates2. Leaking piston reed3. Worn piston/sleeve assembly

blow-by4. Heavy load on evaporator5. Compressor turning slowly6. Belt or clutch slipping

B. DISCHARGE PRESSURE

Low High

N/A 1. Low refrigerant charge2. Cold air across condenser

coil3. Discharge valve plates

leaking4. Piston reed leaking5. Inadequate compressor rpm6. Low side restrictions

1. Overcharge of refrigerant2. Air in the system3. Airflow restricted across

condenser coil: Dirty condenser coil

4. Condenser motor: Low voltage Electrical malfunct ion Fan blade damage/

location5. Restriction in discharge side6. Nitrogen left in system7. Hot air across condenser coil

N/A Does not apply.


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10


Non-Mechanical Cooling Problems

Check the suction line near the compressor. A cool, moist

line is normal. When line condition and refrigeration pres-

sures are near normal, look for problems outside of the

refrigeration system.

1. Excess Cooling Load.a. Open doors.

b. Open windows.

c. Open escape hatch.

d. Large load of passengers.

e. Damaged, deteriorated insulation.

2. Dirty return air filter and/or evaporator coil.

The suction lineshould feel cool orcool and moist

AJA793

AJA794


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11


Conditions that can cause High Discharge Pressure

1. Air or non-condensables in system.

2. Restricted air flow across condenser, dirty condenser

fins, slow fan speed, fans running backwards, etc.

3. A restriction in the high pressure line between the com-

pressor and the receiver tank.

4. Overcharge of refrigerant during warm ambients.

5. Incorrect refrigerant.

6. High ambient temperature.

7. Heavy heat load in bus.

Conditions that can cause Low Discharge Pressure

1. Low refrigerant charge.2. Lowside restriction.

3. Worn compressor.

4. Cold ambient temperature.

5. Incorrect refrigerant.

6. Light heat load in bus.

7. EPR valve closing too soon.

8. Restricted drier.

DiagnosingUsing the

Liquid Line1. The liquid lineshould be

slightly warmer

than the sur-

rounding air.

a. A low refriger-

ant charge may

cause the liquid

line

to be warmer

than normal.

b. A liquid line

restriction will

cause the line to

become cold

after the point of

restriction.

The Liquid lineshould be warmerthan the surrounding air

AJA795


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12


Refrigeration System Access Tools

ACCESS VALVE ACTUATOR TK 204-625

Use the access valveactuator to removerefrigerant or oil from1/4 in. male flare fittings.

Taking a compressor oil sample

QUICK DISCONNECT ACCESS VALVE-TK 204-679Low loss fittings and quick disconnects keep pressure

in the gauge lines when the gauge manifoldis removed from the system.


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13


Use the gauge adapter fitting with pressure gauges to readpressures with minimal refrigerant or oil loss.

GAUGE ADAPTER FITTING TK 204-626

AJA799

Compressor Oil Pressure Receiver Tank Pressure

AJA804


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Service Procedures

14

COMPRESSOR SERVICE VALVES

The suction service valve (SSV) is generally larger than the

discharge service valve (DSV) but is built the same.

Full Out-Valve Back Seated

In 1/2 way-Valve Mid-seated

WARNING: Service valve stems and service ports

must be properly capped and torqued with seals or

O-rings installed. STEMS AND PORTS NOT PROP-

ERLY CAPPED WILL LEAK REFRIGERANT.

AJA803

Full Out,1/4 turn in-Cracked Open to Service Port

Full In-Valve Front Seated

AJA800 AJA802

AJA801

Service PortCap

ServiceValve

Stem Cap

AJA805


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Service Procedures

15

Gauge Manifold Installation(Standard Hose Fittings)1. Remove the large service valve stem caps from the

discharge and suction service valves. DO NOT remove

the small service port caps!

2. Turn both service valves fully counterclockwise to

back-seat the valves and close the service ports.

3. Remove the small service port caps from both service

valves.

4. Attach the low pressure gauge line to the suction ser-

vice port. Leave the fitting loose. (This loose connec-

tion will be used to purge air from the gauge manifold.)

5. Attach the high pressure line to the discharge service

port and secure the line finger tight.

(Continued)

DischargeServiceValve

SuctionServiceValve

AJA806


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Service Procedures

16

6. Turn the discharge service valve stem 1/4-turn clock-

wise to open the service port. (The high pressure

gauge should indicate pressure in the discharge side of

the system.)

7. Open the high side hand valve on the gauge manifo-

fold. Purge air from the gauge manifold service line

(yellow) and tighten the line fitting to the manifold hoseanchor.

8. Open the low side hand valve on the gauge manifold

and allow a small amount of refrigerant to escape from

the loose suction service port fitting and tighten hose

on SSV (This will purge air from the gauge manifold

and the red and blue gauge manifold lines).

9. Close both gauge manifold hand valves.

10. Turn the suction service valve stem 1/4-turn clockwise

to open the service port. (The low pressure gauge

should indicate pressure in the suction side of the sys-

tem.)

WARNING! NEVER operate the compressor with the

discharge service valve front seated. The valve is frontseated when the service valve stem is turned fully

clockwise.

connect tomanifold

DSVvalvecracked

SSVvalveback

seated

AJA807


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Service Procedures

17

Gauge ManifoldInstallation (LowLoss Fittings)

1. Remove the large ser-

vice valve stem caps

from the discharge and

suction service valves.

DO NOT remove the

small service port

caps!

2. Turn both service

valves fully counter-clockwise to back seat

the valves and close

the service ports.

3. Remove the small ser-

vice port caps from

both service valves.

4. Attach the high pres-

sure line (red) to the discharge service port and secure

the line finger tight.

5. Turn the discharge service valve stem 1/4-turn clock-

wise to open the service port. (The high pressure

gauge should indicate pressure in the discharge side of

the system.)

6. Open both hand valves on the gauge manifold.

7. Purge the gauge manifold yellow service line. This is

accomplished by slowly screwing a 1/4 inch flare fitting

into the low loss fitting on the gauge manifold yellow

service line. Allow a small amount of refrigerant to

escape from the service line and then remove 1/4 flare

fitting. Tighten the yellow service line fitting to the

gauge manifold hose anchor. (See illustration)

8. To purge the gauge manifold and low pressure line,

slowly screw a 1/4 inch flare fitting into the low loss fit-

ting on the low pressure (blue) line.

9. Close both gauge manifold hand valves.10. Install the gauge manifold low pressure line (blue) on

the suction service port.

11. Turn the suction service valve stem 1/4-turn clockwise

to open the service port. (The low pressure gauge indi-

cates pressure in the suction side of the system.),

WARNING! NEVER operate the compressor with the

discharge service valve front seated. The valve is front

seated when the service valve stem is turned fully

clockwise.

AJA808


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Service Procedures

18

Removing the Gauge Manifold

NOTE:Minimize oil and refrigerant transfer. Use the fol-

lowing gauge manifold removal procedure to maintain

system integrity without the need to use a different

gauge manifold for each type of refrigerant.

1. Jumper the low pressure cut out.

2. Operate the unit in the cool mode.

3. Back seat the discharge service valve.

4. Open both manifold hand valves.

5. Front seat the suction service valve and pump down

the compressor to a 20 vacuum. Turn the unit off.

6. Establish compressor crankcase pressure between 1and 3 psig.

7. Remove the gauge line from the suction service valve

and cap the service port.

8. Remove the gauge line from the discharge service

valve and cap the service port.

9. Back seat the suction service valve and cap the valve

stem.

10. Cap the discharge service valve stem.

11. Secure all manifold lines to manifold hose anchors

when the manifold is not in use.

12. Remove low pressure jumper and reconnect wiring.


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Service Procedures

19

Check Refrigerant Charge Level

The charge level is very important to the efficient operation

of the unit, therefore, it must be checked as part of the

MONTHLY MAINTENANCE. This service procedure

addresses the method for checking and adding charge as

necessary.

Purpose: To have a charging procedure which will allow an

air conditioning technician to properly charge the system,

without over charging or under charging it, in all weather

conditions.

Scope: This bulletin supersedes all previous charging bul-

letins. This procedure only covers T-Series units with sightglass indicators with a floating ball in the upper half of the

receiver tank.

Procedure:

During a visual check, when the receiver tank ball is not

floating in the upper sight glass, use the following "Top Off

Procedure" to check and replace the required reserve

charge (Locate and repair all leaks to stop further leakage).

1. Follow standard Thermo King procedures and connect

your service gauges to the compressor service valves

or standard access ports. Be sure to purge the air from

your lines.

2. Start the bus and run the engine in the FAST IDLE

MODE with the air conditioning turned on. This shouldbe between 1200 and 1600 compressor rpm. For

buses without the fast idle mode, elevate engine speed

until compressor speed is between 1200 and 1600

rpm.

NOTE: On some applications, a regular low idle engine

speed will not allow you to see the correct refrigerant

level and may result in an improperly charged system.

3. If the system has not been running you must run the

system long enough to separate the compressor oil

from the refrigerant AND pull the bus INTERIOR down

(or up) to WITHIN THE 65 TO 75 DEGREE RANGE.

This may take sometime if conditions are extreme, buta minimum of 15 minutes should be allowed before

checking the charge level.

4. If the COMPRESSOR DISCHARGE PRESSURE is not

ABOVE 250 psig, use a piece of cardboard to partially

cover the condenser coil inlet grille.Do not shut off

condenser fans to raise pressure.This will drive the

pressure up into the range REQUIRED FOR CHECK-

ING AND CHARGING.


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Service Procedures

20

5. Once the conditions of steps 2, 3 and 4 above have

been met, check the ball in the receiver tank upper

sight glass. The proper charge level for this "Top Off"

procedure will have the ball floating at the top of the

upper receiver tank sight glass.

6. If the ball is not at the top of the sight glass, follow stan-

dard Thermo King charging methods, add charge to

the system until the ball floats to the top of the sight

glass.

Note: If the system is low on charge, leak check and

repair accordingly.

Note: Add liquid refrigerant on the low side,increasing the suction pressure no more than 25 psi.

When charging the system from a properly "Evacuated"

condition, (Refer to "Evacuating a System" procedure), we

strongly recommend that you weigh in the charge. This will

save you time and ensure the full reserve charge.

NOTE: Refer to unit maintenance manual specification

section for proper weight charge.

CAUTION: Air in the system will tend to collect in the

receiver tank forcing the refrigerant level down. If youhave air in your system, floating the ball may over-

charge the system. Check your system for air before

letting it go back into service.

CAUTION: AIR IN THE SYTEM WILL ELEVATE OPER-

ATING PRESSURES AND TEMPERATURES, which in

turn will begin a severe degradation process. AND,

which, if left unchanged, will result in system failure

which is NOT COVERED UNDER YOUR THERMO KING

WARRANTY.


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Service Procedures

21

Adding Refrigerant

Todays refrigerants must be added as a liquid. Use this

procedure to add liquid refrigerant to the low side of an

operating unit. Bus should be at fast idle mode, 1200 to

1600 RPM in compressor.

1. Crack the discharge service valve (DSV) and open it to

the service port.

2. Mid-seat the suction service valve (SSV).

3. Set the refrigerant bottle to withdraw liquid refrigerant.

4. Operate the unit in cool and read the suction pressure.

5. Slowly open the gauge manifold low pressure hand

valve until suction pressure rises approximately 25 psigabove the normal operating pressure.

6. Gauge must show 250 lbs. discharge pressure with R-

22 and R-407C refrigerant.

Gauge must show 150 lbs discharge pressure with R-

12 and R-134A refrigerant.

7. Closely watch the receiver tank top sight glass. Imme-

diately stop adding refrigerant when refrigerant is seen

at the top of the sight glass.

8. Close the refrigerant bottle hand valve.

9. Remove the gauge manifold in the recommended man-

ner.

Adding Refrigerant

SSVMidseated

DSVCrackedopen

AJA809


24/75

Service Procedures

22

Charging an Evacuated Unit by Weight

1. Install a gauge manifold. Keep the unit off.

2. Recover the refrigerant and evacuate the system.

3. Place the refrigerant bottle on a scale and attach the

manifolds service line.

4. Open the bottle to withdraw liquid. Purge air from the

service line as required.

5. Record total refrigerant and container weight.

6. Check the unit data plate or unit Maintenance Manual

for refrigerant weight required.

7. Mid seat the compressor discharge service valve.

8. Open the discharge hand valve all the way on thegauge manifold and begin charging the unit. Refriger-

ant flow can be felt as small pulsations on the manifold

service line.

9. Watch the scale and close the hand valve at the refrig-

erant bottle when the correct charge has been added.

10. If refrigerant flow stops before charging is complete,

close discharge manifold hand valve and return the

DSV to the cracked position. Add Liquid refrigerant into

the SSV with the unit running as described in the Add-

ing Refrigerant Procedure.


25/75

Service Procedures

23

UNIT

NOT

RUNING

Drawing shows liquidrefrigerant being added.

DSVvalvemid-seated

SSVvalvecracked

open

AJA810

To charge an evacuated unit, add liquid refrigerant to

the receiver tank or through the discharge service

valve. KEEP THE UNIT OFF.

To charge a running unit, add liquid through the

suction service valve. Control refrigerant flow toincrease suction pressure approximately 25 psi.

UNIT

RUNNING

IN COOL

Drawing shows liquidrefrigerant being added.

SSVvalvemid-seated

DSVvalvecracked open

AJA811


26/75

Service Procedures

24

Date: October 3, 1997

Service Bulletin

Subject: Evaporator Pressure

Regular (EPR) Adjustment

Application: ALL Thermo King Bus

units which are equipped with an

EPR valve.

(THIS PROCEDURE SUPERSEDES ALL PREVIOUS

EPR VALVE ADJUSTMENT PROCEDURES)

Read Me First:The purpose of the EPR valve is to limit how low the pres-

sure inside of the units evaporator coil will go. Holding the

pressure at or above a set value also limits how low the coil

temperature can fall.The pressure and temperature, once

they have moved above the EPR valve setting, are depen-

dent on the heat load being accepted by the unit. The EPR

valve should not allow the pressure to fall below the point of

condensate freezing on the coil. To achieve that, the EPR

valve will stop or restrict the flow of refrigerant to hold the

pressure at or above the set point of the valve.

Once this valve is properly set it does not get out ofadjustment. The valve is factory set, but should be

checked as part of the delivery checkout procedure.

Adjustment if required, should be done by qualified

personnel only. NOTE: Improper adjustment of this

valve may cause damage to the system.

NOTE: The ambient temperature and the bus interior

must be above 80 F.

CAUTION: Do Not attempt to adjust this valve if the

ambient and bus interior temperatures are not above

80 F. Improper setting, and damage to the system may

result.


27/75

Service Procedures

25

Procedure For Checking And Adjusting The EPR Valve.

1. Install service gauges on the compressor and jumper

the low pressure cutout.

2. Install a compound gauge on the pressure tap on the

evaporator side of the EPR valve.

3. Replace all covers removed to install the compound

gauge on the EPR valve.

4. Be careful not to pinch the hose on the compound

gauge, seal all areas that will leak air when the unit is

running.

5. Start the Bus, run at either fast or slow idle for at least

ten minutes. This will return the oil to the compressor.

6. If necessary, turn the heat mode on and raise the inte-rior temperature above 80 F. Then return the unit to the

cool mode.

Note: you will need two people to finish the test.

7. One person raises the engine/compressor speed to

maximum governed speed. (If not governed 2/3-throttle

point.)

Caution: You must increase the compressor speed

(step #7). If you dont, the set point will not be cor-

rect and damage to the refrigeration system may

result.

(continued)


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Service Procedures

26

8. When the Bus engine is maintained at high speed, shut

off the evaporator fan motor(s).

9. Watch the compound gauge installed on the EPR

valve. The pressure will drop and stabilize. This should

take one minute or less.

10. When the compound gauge stabilizes this is the set

point. The set point should be at the pressure stated on

the following table.

11. There should be a large difference between the com-

pound gauge [EPR valve] and the suction service valve

gauge readings (20-30 PSI or the compressor may

even go into a vacuum).

Note: You may need to jumper the low side pres-sure cutout switch to be able to complete this set-

ting procedure.

Lower the engine/compressor speed to high idle and

switch the evaporator fan motor(s) back on.

12. Run the unit at high idle for more than 5 minutes to

clear the liquid refrigerant in the coil or compres-

sor damage may occur.

13. If the EPR valve requires adjustment, turn the adjusting

screw CW to increase the setting (raising coil tempera-

ture/pressure) and CCW to decrease the setting (low-

ering the coil temperature/pressure). Do not turn more

than 1/4 turn at a time.


29/75

Service Procedures

27

14. After every adjustment all covers must be reinstalled

and then run for at least 5 minutes before retesting.

15. If the setting is still incorrect, repeat steps 13 and 14.

16. When the setting is correct, recheck the setting twice

(steps #6 thru #13], you should get the same reading.

17. When the test is complete remove all gauges, jumper

wires and reinstall all covers back.

18. Check the refrigerant charge, oil level and return to ser-

vice.

Filed: F:\Bus\Usrefdat\procedur\eprset.doc

Type of EPR

valve:

ORIT-15 Large

type

ORIT-10 Small type

Refrigerant: Set pressures: Set pressures:

R-134a 24 +/-1 psig 24 +/-1 psig

R-22 50 +/-1 psig 50 +/-1 psig

R-407C 50+/-1 psig 50 +/-1 psig

R-12 27+/-1 psig 27 +/-1 psig


30/75

Service Procedures

28

Low Side Pump Down

Purpose: To test for internal (high side to low side) leaks

and to perform service on the low side without refrigerant

loss.

1. Check gauge manifold hose gaskets. They must not

leak during this test or the system may be contami-

nated with air!

2. Jumper out low pressure cut out (LPCO).

3. Install a calibrated gauge manifold on the SSV & DSV.

4. On units with Orit 10 EPR valve, mount the service

hose from the manifold gauge to the EPR service port.

Then open the low side hand valve.On units with the Orit 15 EPR valve, shut the hand

valve on the pilot valve.

5. Run the unit in cool for ten minutes or longer.

6. Front-seat the receiver tank outlet valve (RTOV).

7. Pump down the lowside to a 25" vacuum.

8. Stop the unit.

9. Observe the low side gauge. Low side pressure should

remain below a 15" vacuum for two minutes or longer.

If pressure rises to zero and stops, there is a low side

leak to the atmosphere.

If pressure continues to rise above zero, the following

may be responsible -

Refrigerant boiling out of the compressor oil. (Restartunit and pump down to 25" vacuum.)

High side to low side leaks at the compressor dis-

charge valve plates or hot gas bypass valve if

equipped.

The following services can be performed with the low side

pumped down and a slight positive pressure established on

the low side:

Add or remove refrigerant oil.

Clean the expansion valve screen.

Change the expansion valve.

Replace the liquid line drier.

Replace the compressor oil filter. Replace lowside tubing.

Replace EPR valve.


31/75

Service Procedures

29

Shut The HandValve on thePilot Valve(Orit 15 only)

AJA813


32/75


33/75

Service Procedures

31

Compressor Oil Pressure Check

1. Install suction pressure gauge

2. Install gauge on compressor port A. It may be neces-

sary to pump down system and use a gauge line with a

schrader valve depresser.

3. With unit running observe gauge reading at compres-

sor oil pump, this is both suction pressure and com-

pressor oil pressure.

4. Read the suction pressure gauge.

5. Calculate oil pressure using the following sample as a

guide:

Pressure from port A 60 PSISuction pressure gauge reading - 25 PSI

Net oil pressure* = 35 PSI*

*Recommended net oil pressure should be

between 15&45 PSI.

PortA

SchraderValvein fitting

60 PSI 15-45PSI

Suction pressureGauge


34/75


35/75

Service Procedures

33

5. Ensure the unit is in COOL cycle. Check the oil level

with a flashlight while unit is operating. The compressor

oil level sight glass should indicate 1/4 to 1/2 full. If indi-

cator reading is low, oil must be added; proceed to

Adding Compressor Oil. If indicator reading exceeds

1/2 level, oil must be removed; proceed to Removing

Excess Oil.

NOTE: The compressor must be pumped down if oil is

added or removed. Pumping down the compressor

causes the oil to indicate lower than during normal

operation. Therefore, it is necessary to carefully note

the difference in oil level between normal operation

and when it is pumped down. Be sure to take this dif-ference into account when adding or removing com-

pressor oil.

Removing Excess Oil

1. Pump the compressor down. Refer to Low Side Pump

Down Procedure or Compressor Pump Down Proce-

dure.

2. After stopping the compressor use the manifold gauge

set to adjust the compressor (low side) pressure to 1 to

3 psi. (Pressure measured at the compressor suction

service valve port).

3. Loosen the drain plug (DO NOT REMOVE) allowingthe oil to drain SLOWLY while watching the level in the

compressor sight glass.

NOTE: Heavy foaming of the oil as it leaves the com-

pressor may indicate an excess of refrigerant in the oil.

Run the system longer to insure a warm sump. Then

recheck level.

4. Tighten the drain plug and leak check.

5. Run the system again and confirm the refrigerant

charge level as well as recheck the oil level before

allowing the bus to return into service.


36/75

Service Procedures

34

Adding Compressor Oil

1. Estimate how much oil will be required to make the

level adjustment.

2. Perform a compressor pump down by following the

procedure indicated in this manual.

3. Stop the bus engine, turn off the bus power and operat-

ing safety switch to insure that no one can start the bus

while you are working on it.

4. Front seat the compressor discharge service valve in

addition to the suction service valve which was front

seated in step #2 above.

5. Balance pressures toestablish positive pressure

and recover excess refrig-

erant pressure.

6. Confirm which oil is to be

added to this system.

7. Hook up a vacuum pump

to your service gauges

which were connected in

step #2.

8. Hook up another service

hose to the oil pressure

port on top of the compres-

sor oil pump at the top rearof the compressor.

9. Open the oil container.

Never leave oil contain-

ers open to the air for

long periods of time.

10. Put the hose from the oil pressure port into the con-

tainer of oil. Turn on the vacuum pump and lower the

pressure inside of the compressor to pull the oil into the

sump through the compressor oil pump until the oil

level is correct.

11. Secure the oil pump pressure port and replace the cap.

Continue evacuating the compressor sump area toremove all air and noncondensable gasses which were

pulled in with the oil.

Balance System

bothvalvesfront-seated

AJA815


37/75

Service Procedures

35

12. When evacuation is complete, back seat all system

valves, start the bus and A/C system and recheck the

compressor oil level.

13. Confirm the system refrigerant charge level, following

the correct procedures (noted in this manual) adjust

charge as required before allowing the bus to return to

service.

CAUTION: Always confirm which oil is in the system

you are servicing before you add oil. The wrong oil can

cause severe damage.

1. Oil Drain Plug 7. Service Manifold Gauge

2. Oil Fill Plug 8. Micron Gauge

3. Oil Pump Port 9. Vacuum Pump

4. Shut-off Valve 10. Measuring Container

Filled w/ Compressor

Oil

5. Discharge Service Port 11. Compressor Oil Sight

Glass

6. Suction Service Port


38/75

Service Procedures

36

Compressor Efficiency Test

Purpose:

Check the discharge valve plate reeds for leakage.

Check the piston reeds for leakage.

Check the piston to sleeve clearance.

1. Install gauge manifold set to monitor system pressures.

2. Bypass the Low Pressure Cutout (LPCO) to prevent

the clutch from disengaging.

3. Start and run the unit at fast idle for 15 minutes to stabi-

lize system pressures.

EXAMPLE: On an 80 F day, your discharge pressure

will be approximately 240 psig.(With R-22 or407-C refrigerant.)

4. Cover the inlet side of the condenser coil to increase

the discharge pressure 70-100 psig higher than nor-

mal.

EXAMPLE: If your discharge pressure is 240 psig after

15 minutes of operation, increase it 310-340 psig.

5. Front seat the suction service valve.

6. When the compressor reaches a 10 vacuum, observe

the discharge pressure. It should read as follows:

A. R-12 & R-134a 125 psig or higher

B. R-22 & R-407C 190 psig or higher

NOTE: If you cant increase the discharge pressurehigher than normal, check the following:

Piston reed(s) or discharge valve plate reed (s) may be

defective.

Compressor may have excessive piston to sleeve

clearance.

Unit may be low on refrigerant.

NOTE: If the compressor will not pull at least a 15 vac-

uum, the piston reed may be defective or the piston to

sleeve clearance may be excessive.

If the compressor will pull a deep vacuum, but not stay

below 15 of vacuum for at least 15 seconds after unitis turned off, the discharge valve reed(s) are defective.


39/75

Service Procedures

37

Air Gap Adjustment

1. Loosen the lock nuts on the three adjustment screws.

2. Using a 3/32 in. (2.4 mm) Allen wrench, turn each

adjustment screw in clockwise (CW) until the armature

bottoms out on the pulley.

3. Back each adjusting screw out counterclockwise

(CCW) 1-1/2 turns. This equals a .045 in. (1.143 mm)

air gap.

4. Double check air gap with feeler gauge per procedure

in step 3 of checking air gap (new clutch only).

5. Tighten the lock nuts. Make sure the adjusting screw

does not turn by holding it with an Allen

wrench.

6. Check the air gap in three different places 120 apart.

NOTE: The clutch should be checked monthly dur-

ing high usage periods

Allen ScrewBottoms OutArmature

AJA817

Wrench Tightening Locknut

3/32 in. (2.4 mm) Allen Wrench


40/75

Service Procedures

38

Testing For Air In The System

Ice Bath Sample Method Test

This inexpensive method requires that a small amount of

the systems refrigerant be placed in a sample bottle and

the bottle submerged in an ice bath.

Required Tools

Manifold Set, Sampling Bottle, Micron Gauge, Vacuum

Pump, Thermometer, Ice Water Bath Consisting of 75%

Ice,

Set of Refrigeration Wrenches to open and close valves.

Manifold Set Hookup Procedure

Attach manifold set as follows:

1. Connect low side hose to sample bottle.

2. Connect center hose to receiver tank service valve.

Valve remains closed.

3. Connect high side hose to evacuation pump.

CAUTION: If hoses are not connected properly, gauge

readings will be inaccurate.

Ice Bath Test Procedure

1. Open manifold gauges and evacuate all hoses, mani-

fold and sample bottle to 500 microns.CAUTION: Check for leaks in the system.

(continued)

AJA819

AJA820


41/75

Service Procedures

39

2. Run the compressor to circulate any air that may be in

the system.

3. Close the high side gauge valve to isolate the micron

gauge and pump.

4. Open the receiver tank service valve to a count of four

(4). Then close the valve and count four (4) again.

5. Then close the low side gauge valve.

6. Place the sample bottle into the ice bath for 15 to 20

minutes. Stir the ice mixture occasionally.

NOTE: An ice water bath must be 75% ice in small

pieces and it should completely cover the sample. The

smaller the tank, the faster the temperature will equal

that of the ice water bath.CAUTION: The procedure of taking the sample is

extremely important to avoid contaminating the

sample.

7. Compare low side gauge reading with your pressure/

temperature chart for 32F (0C).

R-12 = 30 psig (207.5 kPa)

R-22 = 57.5 psig (396.4 kPa)

R-134a = 27.3 psig (188.3 kPa)

R-407c = 50.9 psig (356.3 kPa)

READING MUST BE +/- ONE (1) psig (7 kPa).

If pressures exceed specifications, the refrigerant must be

reclaimed and the unit totally evacuated according toproper evacuation procedures. After the system has been

evacuated, leak tested, and recharged with clean refriger-

ant, reconfirm the system operation. If system operation is

satisfactory, return the bus to service.

CAUTION: If the air and other non-condensables are

not removed, premature system failure will result.

AJA821

AJA822


42/75

Service Procedures

40

Superheat

Expansion Valve Measure (Superheat)

NOTE. Be sure the temperature reading instrument and

compound pressure gauge are accurately calibrated.

Procedure:

1. Pump down the low side into the receiver tank. Open

the receiver tank outlet valve to bleed the pressure

back to 1 to 3 psi in low side.

2. Install pressure gauge in the expansion valve external

equalizer line. This will indicate the pressure directly

and accurately. Use the Temperature Pressure Chart inthis manual to convert the pressure reading into tem-

perature.

Measure suction line temperature at point where feeler

bulb is attached.(See drawing)

3. Open the receiver tank outlet valve and operate the

unit for 15 minutes.

4. Subtract temperature reading obtained by Temperature

Pressure Chart conversion from the suction line tem-

perature to obtain the expansion valve setting (Super-

heat).

Thermo Bulb Suction Line Temperature (F)

-Suction Pressure Temperature Conversion (F)Superheat (F)

NOTE: To establish stable condition, run the unit at

least 15 minutes at 1000 rpm engine speed so the

evaporator air inlet temperature reaches 70.0 to

80.0 (F) (21.0 to 27.0 C). Read pressure and tempera-

ture readings simultaneously. Temperature difference

should be 10.0 to 15.0 (F) (5.5 to 8.0 C).

CAUTION - Thermo King expansion valves are Factory

preset and do not require adjustment. Itis very difficult

to establish controlled conditions in the field to accu-

rately adjust superheat. If it is verified that the super-

heat is out of range and before attempting to adjust theexpansion valve, the following three causes for an out

of range reading MUST be carefully checked.

Check the following:

1. Dirty air filters, or other cause of reduced air flow.

2. Sensing bulb leaking, bulb placed improperly (on refrig-

erant line, or bulb is not properly wrapped with insulat-

ing tape.

3. Kinked capillary tube.


43/75

Service Procedures

41

After these items have been checked and expansion valve

adjustment is unable to bring the superheat measurement

into range, then replace the expansion valve with factory

preset part.

Superheat Adjustment

1. Remove the cap over the adjusting stem.

2. To reduce superheat, turn the adjusting stem counter-

clockwise.

3. Make no more than one 1/4 turn of the stem at one

time, and observe the change in superheat closely to

prevent overshooting the desired setting.As much as

30 minutes may be required to obtain the new bal-ance after the adjustment has been made.

4. When proper readings have been achieved, pump

down the low side into the receiver tank.

5. Remove the pressure gauge from the equalizer line

and thermometer.

6. Install the equalizer line, open the receiver tank and

check for leaks.

WHATS YOUR SUPERHEAT?

52

12

40

66# 52

Example: R-22 Refrigerant

To the suction pressure of 66PSIG

(at compressor)Add estimated suction line loss 2 PSITo obtain suction pressure....68 PSIG (at Bulb)

converted to Temp

Your Superheat is

AJA823


44/75

Notes

42


45/75

Leak Testing/Soldering/Clean-Up

43

Refrigerant Leak Check Toolsand Recommended Testing Procedures

Units low on refrigerant must be tested for leaks and the

leaks must be repaired before adding refrigerant. Following

are recommended tools and testing procedures:

AC & DC Powered Electronic Detectors

DC detectorsnormally use a heated tip and convectional

currents to pull air samples across the sensor. Pumps used

are usually low capacity.

Travel Rate1/2 inch per second.SensitivityAs little as 1/2 oz. refrigerant loss per year.

AC poweredelectronic detectors normally react faster and

are the most reliable. A built-in pump pulls air across the

sensor.

Travel Rate1/2 to 1 inch per second.

Sensitivity1 /10 oz. refrigerant loss per year or less.

Liquid Leak Check Solutions

Leak check solutions are generally acceptable in areas thatare easily reached or where the air is saturated with refrig-

erant. However, several factors determine how well a solu-

tion will work. A good solution should:

Be bubble free

Have a high surface tension

Adhere to and not break away from the joint

Work for several minutes without evaporating

Be commercially made for leak detection


46/75


44

Leak Characteristics

Multiple leaksmay exist. Leak check beyond the first leak.

Component or line temperaturemay determine leak or

leak size. Leak test before and after running the unit.

Circulating refrigerant oil may temporarily plug leaks on

a unit that is operated. When possible, leak check before

running the unit.

Leak Testing Recommendations

Observe lines and components for an oil and dirt accu-

mulationindicating leak location.

Apply liquidbubble solution with soft brushto preventbubbles from forming. Allow several minutes to work,

Blow outconfined areas with compressed air to remove

refrigerant accumulations.

In windy conditions, shieldthe leak area for leak testing.

Electronic Detectors

Calibratefrequently with a standardto be sure of reliabil-

ity.

Calibrate in fresh air toincrease sensitivity.

Calibrate in slightly contaminated air to

reduce sensitivity.Keep sensorfree of dirtand refrigerant oil.

Movesensor slowly(1/2 inch per second).

Start leak testingat the topand work down.


47/75


48/75


46

Good soldering connections are frequently the result of

extensive practice. However, several factors and tech-

niques if properly observed will help ensure success for

even the inexperienced.

Tubing Fit

Too tight a fit between two pieces of swedged tubing may

not permit the solder to flow throughout the joint. Too loose

a fit will also weaken the connection.

A five thousandths of an inch space is recommended

between two pieces of a swedge joint. This is about equal

to two pieces of notebook or typing paper.

Cleanliness

Remove all grease or oil with solvent or clean rags.

Remove oxides from the tubing with scotch brite pads.

Sandpaper and steel wool are not recommended as they

may contaminate the connection or remove excess metal.

Wipe away loose oxide and abrasive particles to prevent

contamination.

Proper Flux

Use recommended fluxes to reduce oxide formation, to aid

in cleaning the connection and to help the solder flow.

AVOID getting flux inside the tubing.

Heat Control

Speed is important. Use a neutral flame large enough to

finish the job quickly and prevent oxide formation.

On swedge connections, heat the male tubing first, then

heat the entire connection evenly.

Cool slowly. Never cool with water or wet rags.


49/75


47

Refrigerant Recoveryand Methods of Recovery

Whenever refrigerant is removed from a refrigeration unit

for service or after leak testing the unit, it must be recov-

ered to limit the potential harm it could cause to the envi-

ronment if it were allowed to escape to the atmosphere.

The following terms are used to refer to the process of

removing, storing and cleaning or purifying refrigerant:

Recovery . The process of removing refrigerant from a unit

and storing it in an external container for later processing.

Recycling . The process of removing moisture and/or oil

from refrigerant to prepare it for reuse.

Reclaiming . The process of cleaning refrigerant to meet

the standards of new refrigerant.


50/75


51/75


49

Recovery from a Working UnitWith An Orit 10 ValveIf a unit is operable and the compressor functions, the

refrigerant should be removed as a liquid. This is the fast-

est and most efficient method. Proceed as follows to

remove refrigerant as a liquid:

1. Install a gauge manifold on the SSV and the RTOV.

Install the service line onto the access port on the Orit

10 EPR valve.

2. Open the manifold low side hand valve.

3. Complete a low side pump down.

4. When you have achieved a 20 vacuum, close the low

side hand valve on the gauge set.5. Remove the service hose from the EPR valve and

attach to the recovery device. (Note: low loss fittings

must be used.)

6. Set the recovery machine for liquid recovery and open

high pressure gauge hand valve. Remove the refriger-

ant through the receiver tank outlet service valve.

7. Recover refrigerant until proper recovery level is

achieved.

Connect serviceline to Orit valveduring low sidepump downonly

Recovery Unit

AJA825


52/75


50

Recovery from a Non-functioning Unit

When a unit is inoperable or the compressor will not func-

tion, the refrigerant must be removed as a vapor. It can be

removed from almost any convenient service port on the

compressor or receiver tank. Because refrigerant must

evaporate in the unit before removal, it is less efficient and

more time consuming than the liquid removal process.

1. On units equipped with an Orit 15 valve or no EPR

valve, attach gauge manifold hoses to the SSV and

DSV. If equipped with an Orit 10 valve, attach the man-

ifold hoses to the discharge valve and to the access

valve on the Orit 10 EPR valve.

2. Open both manifold hand valves.3. Recover vapor refrigerant until proper EPA recovery

levels have been achieved.

Recovery Unit

AJA826


53/75


51

System Evacuation and Clean-up

Refrigeration systems that have had service performed

with the system open to the atmosphere must be evacu-

ated to remove air and moisture that may have entered

during service.

In addition, systems that have been open to the atmo-

sphere for an extended period may require multiple evacu-

ations to be sure all air and moisture are removed.

Refrigeration systems that have had major service or

repairs, and systems suspected of having air, moisture, or

foreign particle contamination, must follow procedures out-

lined in TK 40229, "Clean-up of Refrigeration Systems withThermo King Compressors," and TK 40612, "Evacuation

Station Operation and Field Application

Normal Evacuation Procedure

1. Recover and totally recycle refrigerant making sure

contaminates are removed from the refrigerant using a

certified reclaiming / recycling machine.

2. Properly install evacuation pump and hoses. Attach

one evacuation hose to the receiver tank service valve

(high side) and the other hose to the suction side (low

side) Try to avoid evacuating from schrader valves.

Note: Units with EPR valves must be evacuated from

both sides of EPR valve. Refer to Service Bulletin No.362 dated August, 1989.

3. Properly install micron gauge.

4. Install and tighten stem caps on service valves.

5. Evacuate to 500 microns. Once 500 microns are

reached, evacuate for 30 additional minutes.

(continued)


54/75


52

6. Close off unit from pump, shut pump off.

7. Observe micron gauge. Micron level should not exceed

1500 microns within 5 minutes. Address problem if

gauge exceeds 1500 microns and re-evacuate. Use

nitrogen to purge system before re-evacuating.

Note: Leaks or high levels of moisture are common

reasons for a poor evacuation. Also, check evacuation

equipment and connections, and make sure schrader

valves and service valves are capped. Refer to Service

Bulletin No. 392, dated January, 1990.

8. Weigh in unit charge. (Check unit maintenance manual

for proper charge).

9. Check operating pressures. Ensure the temperature,pressure relation vs. RPMs are within specifica-

tion.Your failure to perform the proper clean-up of the

system may effect unit warranty.

Multiple Evacuation

Perform a multiple evacuation if a system has been open to

the atmosphere for an extended period or as recom-

mended in TK 40229 "Clean-up of Refrigeration Systems

with Thermo King Compressors".

1. Check the evacuation equipment and repair as

required.

2. Open the shut-off valve and place the unit servicevalves in the mid-seat position.

3. Evacuate the system to 2000 microns for 30 minutes.

4. Break the vacuum with nitrogen until a 2 to 5 lb. posi-

tive pressure is established.

5. Allow the nitrogen to remain in the system for 10 min-

utes or more.

6. Evacuate the refrigeration system to 1500 microns for

30 minutes.

7. Break the vacuum with nitrogen until a 2 to 5 lb. posi-

tive pressure is established

8. Change the liquid line drier.

9. Evacuate the system to 500 microns then continue to

evacuate for 30 minutes.

10. Close the hand valves on the gauge manifold.

11. Remove the vacuum pump and charge the unit with

refrigerant.

12. Prepare the unit for service.


55/75


53

Compressor Oil Acid Test (Kit TK 203-346)

An acid test of the compressor oil must be done whenever

an acid condition is suspected. Perform an acid test when-

ever a unit has a substantial refrigerant loss, a noisy com-

pressor or dark/dirty oil as noted in TK 40229 "Clean-up of

Refrigeration Systems with Thermo King Compressors".

To complete an oil acid test:

1. Use an access valve (TK 204-625) on the compressor

oil pump service port and draw an oil sample.

Note: Two Thermo King acid test kits are available -

one for alkybenzene (synthetic) compressor oil and

one for polyolester compressor oil. Be sure to use thecorrect test kit.

Clear Oil Appearance of good oil.

Black Oil Carbonization from operating a unit with

air and moisture in the system.

Brown Oil Results from moisture in the system

causing an acid condition and sub-

sequent copper plating.

Gray/Metallic Caused by wear metal from pistons

bearings, cylinders, etc.

2. Add oil to the test bottle up to the line on the neck.

3. Replace the cover and shake.

4. Compare the oil kit color with the color test strip.


56/75


57/75

Refrigerant Types and Pressures

55

Refrigerant Types/Properties

During unit cooling, refrigerant is the vehicle within the

refrigeration system that picks up the heat inside the bus. It

then carries the heat outside where it can be given up to

the outside air. Following are characteristics of refrigerants

and oils presently used in Thermo King units:

WARNING: Some autos, trucks and other air condition-

ing systems use PAG Polyalkylene Glycol compressor

lubricant. DO NOT mix with Thermo King Ester Base

Oils.

NOTE: Check unit maintenance manual for proper oil

to use on ShuttleAire.

Refrigerant Types/Properties

R-12 Container Color White

Oil Type Mineral Base TK 64-426, or Syn-thetic TK 67-404

Leak Testing Liquid Bubble Solution or CFC


R-22 Container Color Green

Oil Type Synthetic TK 67-404

Leak Testing Liquid Bubble Solution and CFC


R-134a Container Color Light Blue or Brown

Oil Type Polyolester TK 203-413

Leak Testing Liquid Bubble Solution or Halogen

Electronic Detector

R-407C Container Color Medium Brown

Oil Type Polyolester TK 203-413

Leak Testing Liquid Bubble Solution or Halogen

Electronic Detector


58/75

Temperature Pressure Relationships

56


59/75

Temperature Pressure Relationships

57


60/75

Notes

58


61/75

Glossary

59

Bus Air Conditioning Terminology

Absolute Pressure

The pressure above a perfect vacuum, expressed in

pounds per square inch absolute (psia) or kilopascals

(kPa).

Ambient Air

The air surrounding an object.

Ambient Temperature Sensor

Measures outside air temperature and selects the tempera-

ture where the compressor is disabled.

Ambient Temperature

Temperature of the air surrounding an object.

Atmospheric Pressure

The atmosphere surrounding the earth extends many miles

above the surface of the earth. The weight of that atmo-

sphere pressing down on the earth is relatively constant

except for minor changes due to changing weather condi-

tions. As a basic reference for comparison, the atmo-

spheric pressure at sea level has been universally

established at 14.7 psi (100 kPa) and is equivalent to thepressure exerted by a column of mercury 29.92 inches

high. At altitudes above sea level, the depth of the atmo-

spheric blanket surrounding the earth is less; therefore, the

atmospheric pressure is less.

Back Seated Service Valve

The valve stem is backed all the way out (counterclock-

wise). In this position, the valve outlet is open and the ser-

vice port is closed.

Boiling Point

The temperature at which a liquid vaporizes upon the addi-

tion of heat or by the reduction of pressure.

Boost Pump

Increases the flow of engine coolant to the heating coil.


62/75

Glossary

60

Box Temperature

A term use in transport refrigeration that refers to the tem-

perature within a bus body. Box temperature is the same as

return air temperature.

British Thermal Unit (BTU)

The amount of heat required to increase the temperature of

a pound of water one degree Fahrenheit.

Brushless Motor

An alternating current (AC) motor having no commutator or

brushes.

Calorie

The amount of heat required to raise temperature of one

gram of water one degree Celsius.

Capacity

Rate of heat transfer measured in tons, BTUs per hour, K

cal per hours, or Watts. Example: The refrigeration capacity

with R-22 is 125,000 BTU per hour at 2000 RPM and with

R-134a is 100,000 BTU per hour at 2000 RPM

Change of State

The process of changing from a liquid to a gas, gas to liq-uid, solid to liquid, or liquid to solid.

Charge

1) The amount of refrigerant in a system.

2) The process of adding refrigerant to a system.

Check Valve

A valve that allows refrigerant to flow in only one direction.

Coil Drop

The term is often used in reference to the temperature dif-

ference of air entering the evaporator coil versus the tem-

perature out. Coil Drop can also be referred to as

Temperature Differential (TD).

Coil Temperature Sensor

Measures coil temperature, usually on the evaporator coil

to control freezing.


63/75

Glossary

61

Compound Gauge

A gauge that is calibrated in both pounds and inches to

measure pressure and vacuum. This gauge is normally

used to measure low side pressures.

Compressor

The refrigeration component that compresses refrigerant

vapor and creates refrigerant flow.

Compressor Capacity/Efficiency Test

A test used to check the condition of compressor piston

reeds, piston-to-cylinder wall clearance, piston and cylinder

condition, and compressor performance capability.

Compressor Pump Down

A service procedure used to check for internal leaks

through the discharge valve plates, and to perform service

work on the compressor.

Condenser

An arrangement of tubing in which the vaporized and com-

pressed refrigerant is liquefied as heat is removed.

Conduction

Heat transfer between two substances in physical contact.

Convection

Heat transfer between substances through the movement

of a fluid (gas or liquid).

Coolant Valve

Controls coolant flow to the heater coil.

Cool Mode (Reheat Position)

When the unit reaches set point, the clutch remains

engaged while the boost pump operates.

Cool Mode (Cycling Clutch)

When the unit reaches set point, the clutch cycles off. The

unit operates in vent.

Compressor Discharge Sensor

Active above 250F. Senses temperature of discharge gas

leaving the compressor.


64/75

Glossary

62

Dehydration

Process or removing moisture from a refrigeration system

or product. A refrigeration system is considered fully dehy-

drated when it can maintain a 2000 micron vacuum for five

minutes or longer.

Dehydrator

A device used to remove moisture from refrigerant. Drier.

Receiver drier.

Discharge Pressure

Operating pressure measured in the discharge line at the

compressor outlet.

Discharge Temperature

The temperature of refrigerant at the compressor outlet.

Distributor

A device located between the expansion valve and evapo-

rator coil designed to divide the flow of liquid refrigerant

among several parallel paths in the evaporator coil.

Drier

(See Dehydrator)

DSV

Discharge Service Valve

EPROM

Erasable Programmable Read-Only Memory. A program-

mable software chip that can be erased and repro-

grammed.

EPR Valve

Evaporator Pressure Regulator. Controls evaporator coil

temperature to prevent freezing.

Evacuation

The removal of non-condensable gases from the refrigera-

tion system.

Evaporation

A change of state from liquid to vapor.


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Evaporator

The part of the refrigeration system, located in the bus

interior, that absorbs heat during the cooling cycle.

Expansion Valve

A device that meters liquid refrigerant to the distributor and

evaporator coil in direct response to heat load on the evap-

orator.

Flash Gas

The instantaneous vaporization of refrigerant caused by

the reduction of pressure on liquid refrigerant when it

passes through a pressure reducing device.

Foaming

A condition caused by refrigerant boiling out of the com-

pressor oil. Foaming of the compressor oil is often seen

through the compressor oil sight glass for several minutes

after a unit is started.

Fractionation

When a refrigerant blend in the vapor form separates into

its individual refrigerant components.

Freeze PointThe temperature at which a liquid makes a physical change

to a solid. For water this change occurs at 32F (OC).

Freeze Thermostat

Senses and corrects coil freeze-up.

Freeze-Up

1. The formation of ice at the expansion valve.

2. The formation of a solid ice mass over the evaporator

coil reducing air flow.

Front Seated

When the stem of a service valve is turned in (fully clock-

wise) to stop refrigerant flow through the valve. The service

port is open when the valve is front seated.


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Frosting Back

1. The condition of frost formation on the suction line dur-

ing the cooling cycle. This happens when the suction

line temperature is below the dew point.

2. The formation of frost on the suction line, or any portion

of the compressor during the cooling or heating cycle

indicating liquid refrigerant is vaporizing at these loca-

tions.

Gas

Common terminology for refrigerant in the gaseous state.

See Vapor.

Gauge Pressure

The pressure reading measured on a gauge calibrated to

read zero psi (zero kPa) at atmospheric pressure.

Head Pressure

A term commonly used to mean discharge pressure.

Heat

Heat is a form of energy. Heat is often defined as energy in

transfer, for it is never content to stand still, but always

moving from a warm body to a colder body. The terms

warmer and colder are only comparative. Heat exists at anytemperature above absolute zero, even though it may be in

extremely small quantities.

Heat Exchanger

The component in which heat is transferred from one fluid

to the other. Normally, it transfers heat from the liquid line to

the suction line.

Heat Mode

The evaporator fan motor runs at selected speed, the boost

pump and coolant valve are activated, and the condenser

fan motor is stopped.

Heat of Compression

Heat added to refrigerant gas as a result of the work energy

used in compression.

Heat Radiation

Heat transfer through a substance without changing the

substance temperature.


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Heat Transfer

Heat always travels from a warm object to a colder object.

The rate of heat travel is in direct proportion to the temper-

ature difference between the two bodies. Heat can travel in

any of three ways: radiation, conduction, or convection.

Hertz

A unit of electrical frequency equal to one cycle per sec-

ond.

High Pressure Cut Out

A pressure-operated switch that opens to stop unit opera-

tion when discharge pressure reaches a predeterminedmaximum.

High Pressure Relief Valve

A safety valve on the refrigeration system that allows refrig-

erant to escape from the system if pressures exceed a pre-

determined value.

High Side

The portion of the refrigeration system operating under

condensing pressure. That portion of a refrigeration system

between the compressor output and the expansion valve.

Hot Gas Bypass Valve

A solenoid valve controlled by a pressure switch used to

reduce condenser pressure. Excess condenser pressure is

piped to the evaporator inlet.

Inches of Vacuum

Pressure below atmospheric pressure.

Latent Heat

The heat added or removed from a substance that

accounts for a change in state without any measurable

change in temperature. For some substances there are two

conditions where latent heat is required to make the

change of state. They are - changing from a solid to a liquid

called fusion, and from liquid to vapor, or vapor to liquid

called vaporization or condensation.


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Latent Heat of Evaporation

A change of substance from a liquid to a vapor, or from a

vapor back to a liquid involves the latent heat of condensa-

tion. Since boiling is only a rapid evaporating process, it

might also be called the latent heat of boiling, the latent

heat of vaporization, or for the reverse process, the latent

heat of condensation. When one pound of water boils or

evaporates, it absorbs 970 BTU (1023 joules) and to con-

dense one pound of steam to water 970 BTU (1023 joules)

must be extracted from it.

Latent Heat of Fusion

A change of substance from a solid to a liquid, or from a liq-uid to a solid involves the latent heat of fusion. When one

pound of ice melts, it absorbs 144 BTUs, and if one pound

of water is to be frozen into ice, 144 BTUs must be

removed from the water.

Latent Heat of Sublimation

A change in state directly from a solid to a vapor without

going through the liquid phase. The most common example

is the use of dry ice (solid carbon dioxide) for cooling. The

same process can occur with ice below the freezing point,

and is also utilized in some freeze-drying processes at

extremely low temperatures and high vacuums. The latentheat of sublimation is equal to the sum of the latent heat of

fusion and the latent heat of evaporation.

LED

Light Emitting Diode. A small, neon bulb that operates at

low voltage (3 to 4 volts).

Liquid Line

The tube carrying liquid refrigerant from the receiver tank to

the expansion valve.

Load

1. The people being cooled and transported.

2. The amount of heat that is being removed by the refrig-

eration system.

3. The power output of a generator.

4. The resistance of a device to which power is delivered.


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Low Pressure Cut Out

A pressure-operated switch that opens to stop unit opera-

tion when suction pressure reaches a predetermined mini-

mum.

Low Side

The part of a refrigeration system normally under low pres-

sure during the cool mode. (This includes the liquid line

during a low side pump down.)

Motor Driver

DC to AC inverter used to supply voltage to the brushless

AC motor.

Perfect Vacuum

29.92 Hg (29.92 inches of mercury)

Piston Reeds

Ring-shaped reeds (one way valves) located on top of each

piston in a reciprocating compressor. As the piston moves

down in the cylinder, the reed opens to allow refrigerant

gas to move from the crankcase area to the area above the

piston. As the piston moves up in the cylinder, the reed

closes to trap refrigerant gas above the piston. The com-

pressor capacity test is used to check the condition of pis-ton reeds.

Pressure

The push exerted against container walls by a liquid or gas,

usually measured in pounds per square inch or kilopascals

(kPa).

Pressure Drop

1. Loss in line pressure from one point to another due to

restriction.

2. Loss of pressure due to condensing vapor.

3. Loss of pressure due to a leak in the system.

Product

The cargo being temperature-controlled.

PSIA

Pound per square inch - Absolute. See Absolute Pressure.


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PSIG

Pounds per Square Inch Gauge. Pressure in pounds per

square inch as displayed by a gauge calibrated to zero

when open to the atmosphere.

Pump Down

A procedure used to service a refrigeration system. Refrig-

erant in a charged unit is pumped and stored in one part of

the system while servicing another part of the system.

Purging

Releasing a vapor through a refrigeration system to atmo-

sphere to remove contaminants from the system. The rec-ommended vapor used for purging dry nitrogen.

Radiation

Radiation is the transfer of heat by waves similar to light

waves or radio waves. For example, the suns energy is

transferred to the earth by radiation.

Receiver Tank

A refrigerant storage tank.

Reclaim

The process of cleaning refrigerant to like-new condition. Aprocess normally done by a licensed reclaiming service not

an infield practice.

Reclaimer

A machine used for removing refrigerant from a unit,

removing contaminants from the refrigerant, and placing

the refrigerant into a storage container.

Recover

To remove refrigerant from a system and store it in an

external container without testing or processing it.

Recycle

A procedure that removes refrigerant from a unit, cleans

the refrigerant through a series of filters, and returns the

refrigerant to the unit or a bottle.

To clean refrigerant for reuse by removing oil and contami-

nants through single or multiple passes through moisture

absorption devices such as replaceable core filter driers.

Considered an infield practice.


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Refrigerant

The fluid or vehicle used to carry heat from one point to

another in the refrigeration system. It picks up heat as it

vaporizes and gives up heat as it condenses.

Return Air Sensor

Measures coach interior air temperature, usually mounted

in the return air flow of the evaporator.

Return Air Temperature

See Box Temperature.

RTOVAn abbreviation for Receiver Tank Outlet Valve, which is

the service valve on the recovery tank.

Saturated Vapor

The condition when a refrigerant has liquid form present

with the vapor. This occurs in the evaporator when refriger-

ant is making the change from liquid to vapor or in the con-

denser when the refrigerant is condensing.

Saturation Temperature

The condition where temperature and pressure allow both

liquid and vapor to exist simultaneously. A saturated liquidor vapor is one at its boiling point, and for water at sea

level, the saturation temperature is 212 F (I00 C). At higher

pressure, the saturation temperature increases, and with a

decrease in pressure, the saturation temperature

decreases.

Sensible Heat

The heat required to change temperature of a substance.

When the temperature of water is raised from 32 F to 212

F, an increase in sensible heat content is taking place.

Set Point

The temperature selected on a thermostat or micro control-

ler. This is normally the desired temperature.

Short Cycling

The circulation of air from the evaporator outlet and back to

the evaporator inlet without properly circulating through the

load. Short cycling is normally caused by improper ducting

practices. This may also refer to improper clutch operation.


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Sight Glass

A system component that permits visual inspection of oil

and/or refrigerant level and condition.

Slugging

The return of either refrigerant or oil to the compressor in a

liquid condition. Slugging can cause knocking and com-

pressor damage. Sometimes called liquid slugging.

Solenoid Valve

An electromagnet valve that can be opened or closed elec-

trically.

Specific Gravity

Specific gravity (sp.gr.) is a ratio comparing the weight of a

substance to the weight of an equal volume of water. Water

is considered to have a specific gravity of one. Objects

which float on water have a specific gravity of less than

one. Objects which sink in water have a specific gravity

greater than one.

Specific Heat

Heat required to change the temperature of a given unit of

a substance compared to the amount of heat required to

change the temperature of an identical amount of water. Itis expressed in BTUs per pound per degree Fahrenheit or

joules per kilogram kelvin.

SSV

Suction Service Valve.

Suction Line

A flexible line, to absorb vibration, that carries refrigerant

from the evaporator back to the compressor.

Suction Reeds

See Piston Reeds

Superheated Vapor

Vapor that has heat added to it after it has changed from a

liquid to a vapor without any additional change in pressure.


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TD

The abbreviation for Temperature Differential or Tempera-

ture Difference. The term is often used in reference to the

temperature difference of air entering the evaporator coil

versus the temperature out. TD can also be referred to as

Coil Drop.

Temperature

Temperature is the word used to describe the intensity of

heat. In the United States, temperature is normally mea-

sured in degrees Fahrenheit, but the Celsius scale is widely

used in other parts of the world.

Thermodynamics

Thermodynamics is the branch of science that explains the

mechanical action of heat. There are several fundamental

laws of thermodynamics. The first and most important of

these laws is that energy can neither be created nor

destroyed, but can be converted from one type to another.

Thermostat

Controls electrical devices in bus based on temperature.

Ton

The common unit used to measure refrigeration effect. Theamount of heat absorbed by one ton (2000 lb.) of ice as it

changes to liquid over a 24-hour period. It is the refrigerat-

ing equivalent of 12,000 BTUs per hour. (One pound of ice

absorbs 144 B.t.u. As it melts. One ton of ice absorbs

288,000 B.t.u. When one ton of ice melts in 24 hours, the

rate is 288,000 (24 or 12,000 B.t.u. per hour.)

Unloader Valve

Used on some compressors to limit capacity by either shut-

ting off suction gas or bypassing gas back to the suction

side of the compressor.

Valve Plate (Discharge Valve Plate)

An internal part of the compressor located above each pis-

ton. It operates as a check valve, allowing refrigerant gas to

leave the area above the piston while preventing its return

when the piston is on the down-stroke. The compressor

pump down procedure is used to check valve plate condi-

tion.


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Vapor

Common terminology for refrigerant in a gaseous state.

See Gas.

Vent Mode

Coach interior air is recirculated.

Volumetric Efficiency

The ratio of actual volume of refrigerant gas pumped by the

compressor to the volume displaced by the compressor

pistons.

WattA term defining the cooling ability of a unit.

One Watt = 3.42 BTU


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