Carrier EM-17 Operation manual

Transport Air Conditioning
T--336 05/09
OPERATION AND SERVICE
for
EM--17
Large Split Systems
DC12174 & DC12175

OPERATION & SERVICE
MANUAL
MODEL
EM--17
Large Split System
DC12174
DC12175
BUS
AIR CONDITIONING
EQUIPMENT

iT-30805/09
TABLE OF CONTENTS
Section Page................................................................................
SAFETY SUMMARY Safety--1................................................................
DESCRIPTION 1--1..........................................................................
1.1 INTRODUCTION 1--1................................................................
1.1.1 Evaporator Section (EM--17) 1--1....................................................
1.1.2 Condensing Section 1--1............................................................
1.1.3 Compressor Assembly 1--1.........................................................
1.2 SYSTEM OPERATING CONTROLS AND COMPONENTS 1--3............................
1.3 PANEL ASSEMBLY, CONTROL BOX 1--3..............................................
1.4 REFRIGERANT SYSTEM COMPONENT SPECIFICATIONS 1--4..........................
1.5 SAFETY DEVICES 1--5..............................................................
1.6 ELECTRICAL SPECIFICATIONS -- EVAPORATOR (EM--17) MOTOR 1--5..................
1.7 ELECTRICAL SPECIFICATIONS -- Condenser (CM--5) Fan MotorS 1--5....................
1.8 ELECTRICAL SPECIFICATIONS SENSORS 1--5........................................
1.9 SAFETY DEVICES 1--6..............................................................
1.10 AIR CONDITIONING REFRIGERATION CYCLE 1--6.....................................
OPERATION 2--1............................................................................
2.1 STARTING ANDSTOPPING INSTRUCTIONS 2--1.......................................
2.1.1 Starting 2--1.....................................................................
2.1.2 Stopping 2--1....................................................................
2.2 PRE--TRIP--INSPECTION 2--1........................................................
2.3 UNIT OPERATION 2--1...............................................................
2.3.1 Temperature Control 2--1..........................................................
2.3.2 Cooling Mode 2--1................................................................
2.3.3 Vent Mode 2--1..................................................................
2.3.4 Compressor Unloader Control 2--1..................................................
2.3.5 Condenser Fan Control 2--2.......................................................
2.3.6 Compressor Clutch Control 2--2....................................................
2.3.7 Liquid Line Solenoid Control 2--2...................................................
2.4 SEQUENCE OF OPERATION 2--2.....................................................
TROUBLESHOOTING 3--1....................................................................
3.1 System Will Not Cool 3--1.........................................................
3.2 System Runs But Has Insufficient Cooling 3--1.......................................
3.3 Abnormal Pressures 3--1..........................................................
3.4 Abnormal Noise Or Vibrations 3--1..................................................
3.5 Control System Malfunction 3--2....................................................
3.6 No Evaporator Air Flow Or Restricted Air Flow 3--2...................................
3.7 Expansion Valve Malfunction 3--2...................................................
3.8 Heating Malfunction 3--2..........................................................
SERVICE 4--1...............................................................................
4.1 MAINTENANCE SCHEDULE 4--1......................................................
4.2 SUCTION AND DISCHARGE SERVICE VALVES 4--1....................................
4.3 INSTALLING MANIFOLD GAUGE SET 4--2.............................................

iiT-308 05/09
TABLE OF CONTENTS -- Continued:
4.4 PUMPING THE SYSTEM DOWN OR REMOVING THE REFRIGERANT CHARGE 4--3......
4.4.1 System Pump Down For Low Side Repair 4--3.......................................
4.4.2 Refrigerant Removal From An Inoperative Compressor. 4--4...........................
4.4.3 Pump Down An Operable Compressor For Repair 4--4................................
4.4.4. Removing Entire System Charge 4--5...............................................
4.5 REFRIGERANT LEAK CHECK 4--5....................................................
4.6 EVACUATION AND DEHYDRATION 4--5...............................................
4.6.1 General 4--5.....................................................................
4.6.2 Preparation 4--5..................................................................
4.6.3 Procedure for Evacuation and Dehydrating System (Triple Evacuation) 4--5..............
4.6.4 Procedure for Evacuation and Dehydrating System (One Time Evacuation) 4--6..........
4.7 ADDING REFRIGERANT TO SYSTEM 4--7.............................................
4.7.1 Checking Refrigerant Charge 4--7..................................................
4.7.2 Adding Full Charge 4--7...........................................................
4.7.3 Adding Partial Charge 4--7........................................................
4.8 CHECKING FOR NONCONDENSIBLES 4--7...........................................
4.9 CHECKING AND REPLACING HIGH OR LOW PRESSURE SWITCH 4--7..................
4.10 REMOVING TOP COVER (KR--4 CONDENSER) 4--8....................................
4.11 FILTER-DRIER 4--8..................................................................
4.11.1 To Check Filter-Drier 4--8..........................................................
4.11.2 To Replace Filter-Drier 4--8........................................................
4.12 SERVICING THE LIQUID LINE SOLENOID VALVE 4--9..................................
4.12.1 Coil Replacement 4--9............................................................
4.12.2 Internal Part Replacement 4--9.....................................................
4.12.3 Replace Entire Valve 4--9..........................................................
4.13 THERMOSTATIC EXPANSION VALVE 4--9.............................................
4.13.1 Valve Replacement 4--10..........................................................
4.13.2 Superheat Measurement 4--10.....................................................
4.14 REPLACING RETURN AIR FILTERS 4--10.............................................
4.15 COMPRESSOR MAINTENANCE 4--11.................................................
4.15.1 Removing the Compressor 4--11...................................................
4.15.2 Transferring Compressor Clutch 4--12...............................................
4.15.3 Compressor Oil Level 4--12........................................................
4.15.4 Compressor Electric Unloader Operation 4--13.......................................
4.16 TEMPERATURE SENSOR CHECKOUT 4--13...........................................
4.17 REPLACING SENSORS 4--14.........................................................
4.18 ELECTRIC COMPRESSOR UNLOADERS 4--14.........................................
ELECTRICAL 5--1...........................................................................
5--1 INTRODUCTION 5--1................................................................

iii T-30805/09
LIST OF ILLUSTRATIONS
Figure Page.................................................................................
Figure 1--1 Coach Cutaway View 1--2...........................................................
Figure 1--2 Panel Assembly, Control Box 1--3....................................................
Figure 1--3 Relay Board 1--4...................................................................
Figure 1--4 Refrigerant Flow Diageam (DC12175) 1--7.............................................
Figure 1--5 Refrigerant Flow Diagram DC12174 1--8..............................................
Figure 2--1 Thermostat Control Sequence 2--1...................................................
Figure 4--1 Suction or Discharge Service Valve 4--2...............................................
Figure 4--2 Manifold Gauge Set 4--2............................................................
Figure 4--3 Manifold Gauge Set (R-134a) 4--3....................................................
Figure 4--4 Low Side Pump Down Connections 4--4...............................................
Figure 4--5 Compressor Service Connections 4--4................................................
Figure 4--6 System Charge Removal Connections 4--5............................................
Figure 4--7 Vacuum Pump Connections 4--6.....................................................
Figure 4--8 Checking High Pressure Switch 4--8..................................................
Figure 4--9 Condenser Cover Removal 4--8......................................................
Figure 4--10 Filter-Drier Removal 4--8...........................................................
Figure 4--11 Liquid Line Solenoid Valve 4--9......................................................
Figure 4--12 Thermostatic Expansion Valve 4--10.................................................
Figure 4--13 Thermostatic Expansion Valve Bulb and Thermocouple 4--10............................
Figure 4--14 Compressor 4--11.................................................................
Figure 4--15 Removing Bypass Piston Plug 4--11.................................................
Figure 4--16 Compressor Clutch 4--12...........................................................
Figure 4-10. Electric Unloader Schematic 4--14...................................................
Figure 5--1 Electrical Control Panel Relay Board (RB) & Electronic Thermostat (TH) Outline Views. 5--1..
Figure 5--2 Schematic 5--2.....................................................................
LIST OF TABLES
Table Page..................................................................................
Table 1--1 Model 1--2.........................................................................
Table 1--2 Additional Support Manuals 1--2.......................................................
Table 1--3 Unloader Pressure Switch Settings (R--134a) 1--4.......................................
Table 1--4 Safety Devices 1--5..................................................................
Table 3--1 General System Troubleshooting Procedures 3--1.......................................
Table 4--1 Temperature Sensor Resistance 4--13.................................................
Table 4--2 R-134a Temperature - Pressure Chart 4--15............................................

Safety--1 T--33605/09
SAFETY SUMMARY
GENERAL SAFETY NOTICES
The following general safety notices supplement the specific warnings and cautions appearing elsewhere in this
manual. They arerecommendedprecautionsthatmustbeunderstoodandappliedduringoperationandmaintenance
of the equipment covered herein. The general safety notices are presented in the following three sections labeled:
First Aid, Operating Precautions and Maintenance Precautions. A listing of the specific warnings and cautions
appearing elsewhere in the manual follows the general safety notices.
FIRST AID
An injury, no matter how slight, should never go unattended. Always obtain first aid or medical attention immediately.
OPERATING PRECAUTIONS
Always wear safety glasses.
Keep hands, clothing and tools clear of the evaporator, condenser fans & compressor clutch.
No work should be performed on the system until all circuit breakers and start-stop switches are placed in the OFF
position, and power supply is disconnected.
Always work in pairs. Never work on the equipment alone.
In case of severe vibration or unusual noise, stop the system and investigate.
MAINTENANCE PRECAUTIONS
Beware of unannounced starting of the evaporator and condenser fans, and compressor clutch. Do not open the unit
cover before turning power off.
Be sure power is turned off before working on motors, controllers, solenoid valves and electrical controls. Tag circuit
breaker and power supply to prevent accidental energizing of circuit.
Donotbypassanyelectricalsafetydevices,e.g.bridginganoverload,orusinganysortofjumperwires.Problemswith
the system should be diagnosed, and any necessary repairs performed, by qualified service personnel.
When performing any arc welding on the unit, disconnect all wire harness connectors from the modules in the control
box. Do not remove wire harness from the modules unless you are grounded to the unit frame with a static-safe wrist
strap.
In case of electrical fire, open circuit switch and extinguish with CO2(never use water).

Safety--2
T--336 05/09
SAFETY SUMMARY
SPECIFIC WARNINGS AND CAUTIONS
WARNING
Besure to observe warningslisted in thesafetysummaryinthe frontof thismanual beforeperform-
ing maintenance on the hvac system
WARNING
Read the entire procedure before beginning work. Park the coach on a level surface, with parking
brake applied. Turn main electrical disconnect switch to the off position.
WARNING
Do not use a nitrogen cylinder without a pressure regulator.
WARNING
Do not use oxygen in or near a refrigeration system as an explosion may occur.
WARNING
The filter-drier may contain liquid refrigerant. Slowly loosen the flare nuts to avoid refrigerant con-
tact with exposed skin or eyes.
WARNING
Extreme care must be taken to ensure that all the refrigerant has been removed from the compressor
crankcase or the resultant pressure will forcibly discharge compressor oil.
WARNING
Beware of rotating fan blades and unannounced starting of fans or compressor.
CAUTION
To avoid the entrance of air, never evacuate an open drive compressor below 500 microns.
CAUTION
To prevent trapping liquid refrigerant in the manifold gauge set be sure set is brought to suction
pressure before disconnecting.

T--336
1--1
05/09
SECTION 1
DESCRIPTION
1.1 INTRODUCTION
This manual contains Operating Instructions, Service
Instructions and Electrical Data for the Model DC12175
and DC12174 Air Conditioning equipment furnished by
Carrier Transport Air Conditioning as shown in
Table 1--1. Additional support manuals are referenced
in Table 1--2.
The Model DC12175 system consists of a CM--5
condensing unit, an EM--17 evaporator section and a
rear engine compartment mounted 05G compressor.
TheModelDC12174systemconsists ofaKR--4rooftop
condensing unit, an EM--17 evaporator section and a
rear engine compartment mounted 05G compressor.
NOTE
An optional 05K compressor can be used in
place of the 05G in lighter duty applications.
To complete the systems, the air conditioning
equipment interfaces with electrical cabling, refrigerant
piping, duct work and other components furnished by
the bus manufacturer.
Information on the compressor(s) is provided in
separately bound manuals. Refer to Table 1--2.
The drivers control is equipped with a single
HIGH--OFF--LOW switch and A/C Stop Light. The
switch isplaced in the desired fan speed postion to start
temperature control. Operation of the system is
controlled automatically by an electronic thermostat
which maintains the vehicles interior temperature at the
desired set point. Some systems may be configured to
override the high speed selection to low speed once
interior temperature approaches set point. The A/C
Stop Light will be liuminated if the system is shut down
on a safety.
Description of the system components are provided in
the following sub paragraphs and illustrated in
Figure1--1.
1.1.1 Evaporator Section (EM--17)
Theevaporator system includestheevaporatorcoil,fan
and motor assemblies, a thermostatic expansion valve
and condensate drain line connections. Also included
with theevaporator assembly areUPS1, 2& 3, CFS 1&
2, a Liquid Line solenoid (LLS) and Condenser fan
speed resistor.
The thermostatic expansion valve meters the flow of
refrigerant entering the evaporator coil. The evaporator
coil provides heat transfer surface for transfering heat
from air circulating over the coil to refrigerant circulating
inside the tubes; thus providing cooling. The optional
heating coils provide heat transfer surface for
transfering heat from engine coolant water circulating
inside the tubes to air circulating over the outside
surface of the tubes; thus providing heating. The fans
circulate the air over the coils. The air filters remove dirt
particles from the air before it passes over the coils.
1.1.2 Condensing Section
The condensing section includes the condenser coil (s)
fan and motor assemblies, filter--drier, receiver (with
sightglassandmoistureindicator),dischargelinecheck
valve, discharge line connection, service valves, fusible
plug and an ambient temperature sensor.
The discharge check valve is a spring loaded, normally
closed valve that opens with the flow of refrigerant from
the compressor. When the compressor clutch is
disengaged, the discharge check valve will close,
preventing the flow of high pressure liquid from the
condenser back into the compressor.
The condenser coil provides heat transfer surface for
condensing refrigerant gas at a high temperature and
pressure into a liquid at high temperature and pressure.
The condenser fans circulate ambient air across the
outside of the condenser tubes at a temperature lower
than the refrigerant circulating inside the tubes; this
results in condensation of the refrigerant into a liquid.
The receiver collects and stores the liquid refrigerant.
The receiver is fitted with liquid level sight glass to
enable determination of refrigerant liquid level and
moisture content. The receiver is also fitted with a
fusible plug which protectsthe systemfrom unsafe high
pressure conditions. The filter--drier removes moisture
and debris from the liquid refrigerant before it enters the
thermostatic expansion valve. The service valves
enable isolation of the filter--drier for service. The
ambient temperature sensor opens below 50°Fto
prevent A/C operation
1.1.3 Compressor Assembly
The compressor assembly includes the refrigerant
compressor, clutch assembly, suction and discharge
service valves, high pressure switch, low pressure
switch,suctionanddischargeservicing (charging)ports
and electrical solenoid unloaders.
Thecompressorraisesthepressureandtemperatureof
the refrigerant and forces it into the condenser. The
clutch assembly provides a means to disengage the
compressor from the bus engine. The suction and
discharge service valves enable servicing of the
compressor. Suction and discharge servicing
(charging) ports mounted on the service valves enable
connection of charging hoses for servicing of the
compressor, as well as other parts of the refrigerant
circuit. The high pressure switch contacts open on a
pressurerisetoshut downthe system whenabnormally
high refrigerant pressures occur. The electric unloaders
provide a means of controlling compressor capacity,
which enables control of temperature inside the bus.

T--336 1--2 05/09
1
2
3
4
5
6
Figure 1--1 Coach Cutaway View
1Drivers Control
2CM--5 Condenser (DC12175)
3KR--4 Rooftop Condenser (DC12174)
4EM--17 Evaporator Assembly
5Compressor Assembly
6Control Box (TBB)
Table 1--1 Model
MODEL VDC ELECTRONIC
THERMOSTAT COMPRESSOR. CONDENSOR EVAPORATOR
DC12174 24 Yes 05G KR--4 EM--17 Single Loop
DC12175 24 Yes O5G CM--5 EM--17 Single Loop
Table 1--2 Additional Support Manuals
MANUAL/FORM NUMBER EQUIPMENT COVERED TYPE OF MANUAL
T--299PL Split Systems Gen 4/5 Parts List
T--200PL (Old Style) O5G Compressor Parts List
62--02756 (Before SN xxxxx) O5G & O5G Bus Compressor Operation & Service
62--50400 (Old Style) O5G Comp. & Housing Mtd. Clutch Service Training
62--11052 Model 05G Twin Port Compressor Workshop Manual
62--11053 Model 05G Twin Port Compressor Service Parts
62--02460 (Optional) Model O5K Compressor Service Parts
62--02491 (Optional) Model O5K Compressor Operation & Service

T--336
1--3
05/09
1.2 SYSTEM OPERATING CONTROLS AND
COMPONENTS
1 Electronic Thermostat (TH)
The system is equipped with an electronic
thermostat which operates in combination with a
separate relay board (See Figure 1--2 & Figure 1--3) to
control the operation of the system.
The setpoint is adjusted by manually turning the
controlboxmountedpotentiometertowards“COOLER”
or “WARMER”.
The thermostat’s temperature sensor monitors the
vehicles interior temperature at the return air section of
theevaporatorandcontrolsthe operatingfunctionofthe
system to maintain the desired vehicle interior
temperature.
2 Manual Switches
A/C Mode Switch (ACMS)
The drivers control is equipped with a single
HIGH--OFF--LOW switch. The switch is placed in the
desired fan speed postion to start temperature control.
3 Pressure Switches
Condenser Fan Switches (CFS)
The condenser fan switches are located in the
evaporator section. Switch CFS 1 controls the number
of fans in operation while switch CFR2 controls fan
speed.
1.3 PANEL ASSEMBLY, CONTROL BOX
91--62011
RELAY BOARD (See Figure 1--3)
POTENTIOMETER ELECTRONIC THERMOSTAT
Figure 1--2 Panel Assembly, Control Box