Carrier AC310 Operation manual

Transport Air Conditioning
T--304 Rev A Change 07/09
OPERATION AND SERVICE
for
MODELS AC310 & AC350
Rooftop Air Conditioning Units
With
BT324 Carrier Sutrak Digital Display (CSDD)
or
280P/282P Electronic Thermostat

OPERATION AND
SERVICE MANUAL
TRANSPORT
AIR CONDITIONING UNIT
MODELS
AC310 & AC350
ROOFTOP AIR CONDITIONING UNITS
*CSDD -- BT324 (*Carrier Sutrak Digital Display)
Electronic Thermostat -- 280P & 282P

iT--30404/08
TABLE OF CONTENTS
PARAGRAPH NUMBER Page
SAFETY SUMMARY Safety--1....................................................................
DESCRIPTION 1--1...............................................................................
1.1 INTRODUCTION 1--1.....................................................................
1.2 GENERAL DESCRIPTION 1--2.............................................................
1.2.1 Rooftop Unit 1--2......................................................................
1.2.2 Condensing Section 1--2...............................................................
1.2.3 Evaporator Section 1--4................................................................
1.2.4 Drivers Evaporator (Optional) 1--6.......................................................
1.2.5 Compressor Assembly 1--6.............................................................
1.2.6 System Operating Controls And Components 1--7.........................................
1.2.7 280P & 282P (PWM) Electronic Thermostat Controller 1--7.................................
1.2.8 CSDD BT--324 (Carrier--Sutrak Digital Display) Microprocessor 1--7..........................
1.2.9 Motor Fault Board (Optional) 1--7........................................................
1.3 REFRIGERATION SYSTEM COMPONENT SPECIFICATIONS 1--7.............................
1.4 ELECTRICAL SPECIFICATIONS -- MOTORS 1--7............................................
1.5 SAFETY DEVICES 1--8...................................................................
1.6 AIR CONDITIONING REFRIGERATION CYCLE 1--8..........................................
1.7 HEATING CYCLE 1--8....................................................................
OPERATION (Manual Controller) 2--1..............................................................
2.1 STARTING, STOPPING AND OPERATING INSTRUCTIONS 2--1..............................
2.1.1 Starting 2--1..........................................................................
2.1.2 Stopping 2--1.........................................................................
2.2 PRE--TRIP INSPECTION 2--1..............................................................
2.3 MODES OF OPERATION 2--2.............................................................
2.3.1 Temperature Control 2--2...............................................................
2.3.2 Cooling Mode 2--2.....................................................................
2.3.3 Heating Mode 2--2.....................................................................
2.3.4 Boost Pump (Optional) 2--2.............................................................
2.3.5 Vent Mode 2--2.......................................................................
2.3.6 Compressor Unloader Control (Only with 05G or 05K Compressors) 2--2.....................
2.3.7 Override Mode -- AC310 (Dehumidification) 2--2..........................................
2.3.8 Evaporator Fan Speed Selection 2--3....................................................
2.3.9 Compressor Clutch Control 2--3.........................................................
(A--6, TM--16, TM--21) 2--3....................................................................
2.4 SEQUENCE OF OPERATION (280P / 282P) 2--3.............................................
2.4.1 Electronic Thermostat 2--3.............................................................
OPERATION BT324 Controller 3--1.................................................................
3.1 STARTING, STOPPING AND OPERATING INSTRUCTIONS 3--1..............................
3.1.1 Starting 3--1..........................................................................
3.1.2 Stopping 3--1.........................................................................
3.2 PRE--TRIP INSPECTION 3--1.............................................................
3.3 SEQUENCE OF OPERATION BT324 CSDD 3--2.............................................
3.3.1 Function of Keys when “Engine On” and controller active: 3--2...............................
3.3.2 Illuminating Indications (Display) 3--2....................................................

ii
T--304 04/08
TABLE OF CONTENTS Continued:
3.4 Operating Instructions BT324 3--2...........................................................
3.4.1 Display 3--2..........................................................................
3.4.2 Interior Temperature Control 3--2........................................................
3.4.3 Ventilation 3--2........................................................................
3.4.4 Reheat (optional) 3--3..................................................................
3.4.5 Temperature Indication 3--3.............................................................
3.5 CHANGING BETWEEN 5F (FAHRENHEIT) AND 5C (CELCIUS ) 3--3..........................
TROUBLESHOOTING 4--1.........................................................................
4.1 System Will Not Cool 4--1..............................................................
4.2 System Runs But Has Insufficient Cooling 4--1............................................
4.3 Abnormal Pressures 4--1...............................................................
4.4 Abnormal Noise Or Vibrations 4--1.......................................................
4.5 No Evaporator Air Flow Or Restricted Air Flow 4--2........................................
4.6 Expansion Valve Malfunction 4--2........................................................
4.7 Heating Malfunction 4--2...............................................................
SERVICE 5--1....................................................................................
5.1 MAINTENANCE SCHEDULE 5--1...........................................................
5.2 REMOVING EVAPORATOR COVER 5--1....................................................
5.3 REMOVING CONDENSER COVER 5--1.....................................................
5.4 INSTALLING MANIFOLD GAUGE SET 5--1..................................................
5.4.1 Installing R--134a Manifold Gauge/Hose SET 5--1.........................................
5.5 PUMPING THE SYSTEM DOWN OR REMOVING THE REFRIGERANT CHARGE 5--2...........
5.5.1 System Pump Down For Low Side Repair 5--2............................................
5.5.2 Removing Entire System Charge 5--3....................................................
5.6 REFRIGERANT LEAK CHECK 5--3.........................................................
5.7 EVACUATION AND DEHYDRATION 5--3....................................................
5.7.1 General 5--3..........................................................................
5.7.2 Preparation 5--3.......................................................................
5.7.3 Procedure for Evacuation and Dehydrating System 5--3....................................
5.8 ADDING REFRIGERANT TO SYSTEM 5--3..................................................
5.8.1 Checking Refrigerant Charge 5--3.......................................................
5.8.2 Adding Full Charge 5--4................................................................
5.9 CHECKING FOR NONCONDENSIBLES 5--4................................................
5.10 CHECKING AND REPLACING HIGH OR LOWPRESSURE CUTOUT SWITCH 5--4..............
5.10.1 Replacing High Or Low Pressure Switches 5--4...........................................
5.10.2 Checking High Or Low Pressure Switches 5--4............................................
5.11 FILTER-DRIER 5--5.......................................................................
5.11.1 To Check Filter--Drier 5--5..............................................................
5.11.2 To Replace Filter--Drier Assembly 5--5...................................................
5.12 SERVICING THE HEAT VALVE 5--5........................................................
5.12.1 Coil Replacement 5--6.................................................................
5.12.2 Internal Part Replacement 5--6..........................................................
5.12.3 Replace Entire Valve 5--6
..............................................................

iii T--30404/08
TABLE OF CONTENTS Continued:
5.13 SERVICING THE LIQUID LINE SOLENOID VALVE 5--6.......................................
5.13.1 Coil Replacement 5--6.................................................................
5.13.2 Internal Part Replacement 5--6..........................................................
5.13.3 Replace Entire Valve 5--6...............................................................
5.14 SERVICE VALVES 5--7....................................................................
5.15 REPLACING RETURN AIR FILTERS 5--7...................................................
5.16 THERMOSTATIC EXPANSION VALVE 5--8..................................................
5.16.1 Valve Replacement 5--8................................................................
5.16.2 Superheat Measurement 5--9...........................................................
ELECTRICAL 6--1................................................................................
6.1 INTRODUCTION 6--1.....................................................................
LIST OF FIGURES
Figure 1--1 AC310/350 Rooftop Units 1--2...........................................................
Figure 1--2 Condensing Section Components (AC310 -- Dual Loop -- GEN I) 1--3..........................
Figure 1--3 Condensing Section Components (AC350 Single Loop -- GEN II) 1--4.........................
Figure 1--4 Evaporator Section Components (AC310 --Dual Loop -- GEN I) 1--5...........................
Figure 1--5 Evaporator Section Components (AC350 Single Loop -- GEN II) 1--6..........................
Figure 1--6 Refrigerant Flow Diagram -- Cooling (Dual Loop) 1--9...........................................
Figure 1--7 Flow Diagram -- Heating 1--10...............................................................
Figure 1--8 Refrigerant Flow Diagram, Cooling (Single Loop) AC350 1--11.................................
Figure 1--9 Sheet 1 -- Electrical Control Board (280P) 1--12.............................................
Figure 1--9 Sheet 2 Legend 1--13....................................................................
Figure 1--10 AC350 With BT324 Control 1--14.........................................................
Figure 1--11 Motor Fault Board (Optional) 1--15........................................................
Figure 2.1 Control Switches (Typical) 2--1..............................................................
Figure 2.2 280P / 282P Thermostat 2--3.............................................................
Figure 3--1 Bus Dash With A/C Switch & BT324 CSDD Controller 3--1...................................
Figure 3--2 BT324 CSDD Controller 3--2.............................................................
Figure 5--1 Manifold Gauge Set (R--134a) 5--2........................................................
Figure 5--2 In--Line Service Connections 5--3.........................................................
Figure 5--3 Checking High Pressure Switch 5--4......................................................
Figure 5--4 Filter--Drier Removal 5--5................................................................
Figure 5--5 Heat Valve 5--6........................................................................
Figure 5--6 Liquid Line Solenoid Valve 5--7...........................................................
Figure 5--7 Service Valve R134a (High Side) 5--7.....................................................
Figure 5--8 Return Air Grill Assembly With Air Filter Showing 5--7.......................................
Figure 5--9 Diffuser and Filter Element 5--8..........................................................
Figure 5--10 Filter, Diffuser and Composit Frame 5--8.................................................
Figure 5--11 Return Air Grill Assembly With Diffuser And Composit Frame Showing 5--8...................
Figure 5--12 Thermostatic Expansion Valve 5--8......................................................
Figure 5--13 Thermostatic Expansion Valve Bulb and Thermocouple 5--9.................................
Figure 6--1 System Controls (Typical) 6--2...........................................................
Figure 6--2 Manual Controls With Manual Reheat Control (Sheet 1) 6--3.................................
Figure 6--3 Manual Controls With Manual Reheat Control (Sheet 2) 6--4.................................

iv
T--304 04/08
LIST OF FIGURES Continued:
Figure 6--4 Evaporator Motors 1 -- 4 6--5.............................................................
Figure 6--5 Evaporator Motors 5 -- 8 6--6.............................................................
Figure 6--6 Condenser Motors 6--7..................................................................
Figure 6--7 BT324 Controls With (1) Compressor (AC350) 6--8.........................................
Figure 6--8 BT324 Control Circuit (AC350) 6--9.......................................................
Figure 6--9 BT324 Evaporator Motors (AC350) 6--10...................................................
Figure 6--10 CSDD BT324 Condenser Motors 6--11....................................................
Figure 6--11 AC350 With BT324 Control 6--12.........................................................
Figure 6--12 CSDD BT324 Control Circuit 6--13........................................................
Figure 6--13 CSDD BT324 6--14.....................................................................
Figure 6--14 Thermostat (One/Two Compressors) 6--15................................................
Figure 6--15 Thermostat (One/Two Compressors) 6--16................................................
Figure 6--16 Thermostat (One/Two Compressors) 6--17................................................
Figure 6--17 Thermostat (One/Two Compressors) 6--18................................................
Figure 6--18 Thermostat (One/Two Compressors) 6--19................................................
LIST OF TABLES
Table 1--1 AC310 Models 1--1.......................................................................
Table 1--2 AC 350 Models 1--1......................................................................
Table 1--3 Additional Support Manuals 1--1............................................................
Table 2--1 Unloader UV1 Relay 2--2..................................................................
Table 2--2 Unloader UV2 Relay 2--2..................................................................
Table 4--1 General System Troubleshooting Procedures 4--1............................................
Table 5--1 R-134a Temperature - Pressure Chart 5--10..................................................

Safety--1 T--304
04/08
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. 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 and condenser fans.
No workshould beperformed onthe unituntil allstart-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 unit and investigate.
MAINTENANCE PRECAUTIONS
Beware of unannounced starting of the evaporator and condenser fans. 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--304 04/08
SPECIFIC WARNINGS AND CAUTIONS
WARNING
Be sure to observe warnings listed in the safety summary in the front of this manual before per-
forming maintenance on the hvac system
WARNING
Read the entire procedure before beginning work. Park the vehicle on a level surface, with park-
ing 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 Connecting Nuts And Avoid
Contact With Exposed Skin Or Eyes.
CAUTION
The AC310 & AC350 Rooftop Systems have R134a service port couplings installed on the compres-
sor and 1/4 inch flare (Acme) fittings installed on the unit piping.
CAUTION
To prevent trapping liquid refrigerant in the manifold gauge set be sure set is brought to suction
pressure before disconnecting.

1--1 T--304
04/08
SECTION 1
DESCRIPTION
1.1 INTRODUCTION
This manual contains Operating Instructions, Service
Instructions and Electrical Data for the Model AC310
and AC350 Air Conditioning and Heating equipment
furnished by Carrier Transport Air Conditioning as
shown in Table 1--1 and Table 1--2.
Model AC310/350 systems consists of a Rooftop unit
containing the condensing section, the evaporator
section and engine compartment mounted
compressor(s). To complete the system, the air
conditioning and heating equipment interfaces with an
optional drivers evaporator (dash--air), electrical
cabling, refrigerant piping, engine coolant piping (for
heating), duct work and other components furnished by
Carrier Transport Air Conditioning and/or the bus
manufacturer.
Additional support manuals are shown in Table 1--3.
Operation of the unit is controlled automatically by an
electronic thermostat. The controlls maintain the
vehicle’s interior temperature at the desired set point.
Table 1--1 AC310 Models
Model AC310 Voltage Controller With Heat Dual Loop Single Loop W/Covers
77--62031--00 12 VDC Manual (280P) Yes X X
77--62031--01 24 VDC Manual (280P) Yes X X
77--62031--02 12 VDC BT324 Yes X X
77--62031--03 24 VDC BT324 Yes X X
77--62032--00 12 VDC Sytronic System
& Manual (280P) Yes X X
77--62032--01 24 VDC Manual (280P) Yes X X
77--62032--02 -- -- -- -- -- --
77--62032--03 12 VDC Manual (280P) Yes X X
77--62032--04 12 VDC Manual (280P) Yes X X
77--62032--05 12 VDC BT324 Yes X X
*77--62032--06 12 VDC BT324 (Tropic) Yes X X
*NOTE: 77--62032--06 (Tropic) -- Has an AC310 Evaporator Section & an AC350 Condenser Section.
Table 1--2 AC 350 Models
Part Number Voltage Controller With Heat Dual Loop Single Loop W/Covers
77--62041--00 24 VDC -- -- -- X--
77--62041--01 24 VDC Manual Yes -- Yes
77--62041--02 24 VDC Manual Yes XNo
77--62041--03 24 VDC -- -- -- -- --
77--62041--04 24 VDC BT324 No XNo
77--62041--05 24 VDC BT324 No XYes
77--62041--06 24 VDC BT324 Yes XYes
77--62041--07 24 VDC BT324 Yes XNo
77--62041--10 24 VDC BT324 Yes XYes
Table 1--3 Additional Support Manuals
MANUAL NUMBER EQUIPMENT COVERED TYPE OF MANUAL
T--304PL AC--310/350 Service Parts List
T--200PL 05G Compressor Service Parts List
62--02756 05G Compressor Operation & Service
62--11052 05G Compressor -- Twin Port Workshop Manual
62--11053 05G Compressor -- Twin Port Service Parts List
62--02460 05K Compressor Service Parts List
62--02491 05K Compressor Operation & Service

1--2
T--304 04/08
1.2 GENERAL DESCRIPTION
1.2.1 Rooftop Unit
The rooftop unit includes the condenser section and the evaporator section (See Figure 1--1).
AC310
AC350
Condenser Section
Evaporator Section
Condenser Section
Evaporator Section
Figure 1--1 AC310/350 Rooftop Units
1.2.2 Condensing Section
The dual (See Figure 1--2) and single loop (See
Figure 1--3)condensingsectionsinclude thecondenser
coils, four (4) or six (6) fan and motor assemblies,
filter-driers, receivers, and filter drier service valves.
The condenser coils provide 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 refrigerant circulating inside the tubes; this results
in condensation of the refrigerant into a liquid. The
filter-drier removes moisture and debris from the liquid
refrigerant before it enters the thermostatic expansion
valve in the evaporator assembly. The service valves
enable isolation of the filter-drier for service.
The receiver collects and stores liquid refrigerant. The
receiver is also fitted with a pressure relief valve which
protects the system from unsafe high pressure
conditions.

1--3 T--304
04/08
1
2
3
4
5
7
8
45
6
1
3
3
2
99
AC310
Dual Loop
9
1. Condenser Coil Assembly
2. Receiver
3. Service Valve (High Side)
4. Filter Drier Upper Support
5. Filter Drier
6. Filter Drier Lower Support
7. Condenser Fan and Motor Assembly
8. Condenser Motor Support
9. Discharge Line Check Valve (Location)
Figure 1--2 Condensing Section Components (AC310 -- Dual Loop -- GEN I)

1--4
T--304 04/08
1
2
3
4
5
12
44
5
1 Condenser Coil Assembly
Receiver Tank (Part Of Coil Assembly)
2 Service Valve
3 Filter Drier
4 Fan & Motor
5 Frame (Aluminum)
Figure 1--3 Condensing Section Components (AC350 Single Loop -- GEN II)
1.2.3 Evaporator Section
The dual loop AC310 & AC350 (GEN I) evaporator
section (See Figure 1--4) includes the evaporator coils,
eight (8) or twelve (12) single--shafted blower/motor
assemblies, two heater coil assemblies, two
thermostatic expansion valves, two liquid line solenoid
valves, and condensate drain connections.
NOTE
The GEN I series of AC310 & AC350 evapora-
tors are supplied with single shaft blower/motor
assemblies. The GEN II series have dual shaft
blower/motor assemblies.
The single loop AC310 & AC350 evaporator section
(See Figure 1--5) includes the evaporator coils, four (4)
or six (6) double--shafted blower/motor assemblies,
heater coil assemblies, one thermostatic expansion
valve, one liquid line solenoid valve (to add in--dash
service port), and condensate drain connections.
The liquid line solenoid valve closes whenthe system is
shut down to prevent flooding of coils and the
compressor with liquid refrigerant. The evaporator coils
provide heat transfer surface for transferring heat from
air circulating over the outside of the coil to refrigerant
circulating inside the tubes; thus providing cooling. The
heating coils provide a heat transfer surface for
transferring 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
particlesfrom the airbeforeit passesover the coils. The
thermostatic expansion valve meters the flow of
refrigerant entering the evaporator coils. The heat valve
controls the flow of engine coolant to the heating coils
upon receipt of a signal from the controller. The
condensate drain connections provide a means for
connectingtubingfordisposingof condensatecollected
on the evaporator coils during cooling operation.

1--5 T--304
04/08
1
2
3
4
4
5
6
6
7
8
9
Return Air
Section
AC310
Dual Loop
1. Evaporator Coil Assembly
2. Heater Coil
3. Expansion Valve
4. Evaporator Blower Assembly
5. Evaporator Motor
6. Sight Glass
7. Heating Line
8. Access Port
9. Liquid Line Solenoid
Figure 1--4 Evaporator Section Components (AC310 --Dual Loop -- GEN I)

1--6
T--304 04/08
1
1
2
2
3
4
4
6
8
5
6
7
1. Evaporator Coil Assembly
2. Heater Coil
3. Expansion Valve
4. Evaporator Blower/Motor Assembly
5. Control Panel
6. Heater Line
7. Front Evaporator Port
8. Liquid Line Solenoid
Figure 1--5 Evaporator Section Components (AC350 Single Loop -- GEN II)
1.2.4 Drivers Evaporator (Optional)
The drivers evaporator assembly isnormally installedin
thevehicledashareaandinterfaceswiththerooftopunit
electrical cabeling and refrigerant piping.
The drivers evaporator assembly includes an
evaporator coil, thermal expansion valve, blower motor
assembly and a condensate drain connection. Refer to
the OEM technical literature for driver’s evaporator
information.
1.2.5 Compressor Assembly
a. Dual Loop Compressors A--6 & TM--21
The standard AC310 dual loop compressor assembly
includes the refrigerant compressor, clutch assembly,
in--line high & low pressure switches, suction
accumulator and in--line suction and discharge
servicing (charging) ports.
b. Single Loop Compressor TM--31
The TM--31 compressor assembly used only with the
AC310 Single Loop Unit includes the refrigerant
compressor, clutch assembly, suction & discharge
service valves, high pressure switch, low pressure
switch, suction accumulator and suction and discharge
servicing (charging) ports.
c. Single Loop Compressors 05G & 05K
The 05G (AC350) & 05K (AC310) compressor
assemblies used with the single loop units, includes the
clutch assembly, suction & discharge service valves,
high pressure switch, low pressure switch, suction and
discharge servicing (charging) ports and electric
solenoid unloaders.
Thecompressorraisesthepressureandtemperatureof
the refrigerant and forces it into the condenser coil
tubes. Theclutch assembly provides ameans of driving
the compressors by the vehicle engine. Suction and
discharge servicing (charging) ports mounted on the
compressor fittings 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 pressure rise to shut down the
system when abnormally high refrigerant pressures
occur.
The electric unloaders (05G & 05K) provide a means of
controlling compressor capacity, which enables control
of temperature inside the vehicle. The suction and
discharge service valves enable servicing of these
compressors.

1--7 T--304
Change 07/09
1.2.6 System Operating Controls And Compo-
nents
Thesystemisoperatedbyanelectronicthermostattype
controller and/or manually operated switches. The
manually operated switches are located on the drivers
control and may consist of a single ON/OFF switch or
additional switches. The controller regulates the
operational cycles of the system by energizing or
de--energizing relays on the relay board in response to
deviations in interior temperature. Modes of operation
includeCoolingandHeating.Onsystemsfittedwithonly
an ON/OFF switch, the controller will cycle the system
between the operating modes as required to maintain
desired set point temperature (See Section 6 for wiring
diagrams).
In the heat mode the heat valves are opened to allow a
flow of engine coolant through the heat coils located in
the evaporator section. The evaporator fans operate to
circulate air over the heat coils in the same manner as
the cooling mode.
In the cooling mode the compressor is energized while
the evaporator and condenser fans are operated to
provide refrigeration as required. The compressor (s)
capacity is matched to the bus requirements. Once
interior temperature reaches the desired set point, the
compressor(s) is deenergized.
1.2.7 280P & 282P (PWM) Electronic Thermostat
Controller
This type controllerhas three(3) modes, Cool, Ventand
Heat.
The range on the potentiometer is 62.6°-- 86°F
(17--30°C).
1.2.8 CSDD BT--324 (Carrier--Sutrak Digital Display)
Microprocessor
This Carrier Sutrak Digital Display (BT--324) controller
has three (3) modes, Auto, Vent (Cycleclutch type) and
Heat.
1.2.9 Motor Fault Board (Optional)
The motor fault board (See Figure 1--11) consists of red
and green LED’s, which when illuminated, will reflect
each motors state of condition. When the evaporator
and condenser motors are energized, the green LED’s
will be illuminated. If a red LED is energized, it will show
an “open circuit” condition, indicative of a motor failure.
The green LED will not be illuminated at this time. The
motor fault board is a seperate circuit board that is
located at the return air section. The return air grill is
oppened to view the LED indicators.
1.3 REFRIGERATION SYSTEM COMPONENT
SPECIFICATIONS
a. Refrigerant Charge R--134a (Approximate)
NOTE
Refrigerant charge will depend on hose lengths
and diameters; or if there is an In--Dash unit
(front evaporator). The following should onlybe
used as a guideline.
AC310 Dual Loop A--6 or TM--21 Compressor
6 Pounds (2.7 kg) -- Curbside
8 Pounds (3.6 kg) -- Roadside
AC310 -- Single Loop TM--31 Compressor
12 Pounds (5.4 kg) without In--Dash unit
AC310 -- Single Loop 05G or 05K Compressor
13.2 to 15.4 Pounds (6.0 to 7.0 kg) without
In--Dash unit
AC350 -- Single Loop 05G or 05K Compressor
16.5 to 18.7 Pounds (7.5 to 8.5 kg) without
In--Dash unit
For systems with In--Dash unit (Optional)
Add 2 pounds (0.9 kg) to above listed charge.
b. Compressors
CompressorA6 (No longer Available)
Weight, (Dry) 34.5 Lbs.
Oil Charge 10 Oz. PAG (07--00333--00)
Compressor TM--21
Weight, (Dry) 7.5 Lbs. (3.4 kg)
Oil Charge 6.1 Oz. (180 cc) PAG
(46--50006--00)
Compressor TM--31
Weight, (Dry) 21 Lbs.
Oil Charge 16.9 Oz. (500cc) PAG
(46--50006--00)
Compressor Carrier 05K
Weight, (Dry) 108 Lbs.
Oil Charge 5.5 Pints POE
(07--00317--00pk6)
Compressor Carrier 05G
Weight, (Dry) 146 Lbs. W/Clutch
Oil Charge 7.75 Pints POE
(07--00317--00pk6)
c. Thermostatic Expansion Valve:
Superheat Setting (Externally Adjustable) Factory
Setat9to18°F(±4°F) MOP Setting: 55 ±4 psig
(3.74 ±2.27 bar)
d. High Pressure Switch (HPS) Normally Closed
Opens at: 360 ±10 psig (20.41 ±0.68bar)
Closes at: 280 ±10 psig (13.61 ±0.68bar)
e. Low Pressure Switch (LPS) Normally Open
Opens at: 6 ±3psig (0.41 ±0.20 bar)
Closes at: 25 ±3psig(1.7±0.20 bar)
f. Water Temperature Switch (WTS)
[Bus Manufacturer Supplied -- Suggested close on
temperature rise at 105°F(41°C)]
1.4 ELECTRICAL SPECIFICATIONS -- MOTORS
a. Evaporator Blower/Motor
Evaporator Motor Permanent Magnet
24 VDC 12 VDC
Horsepower (kW) 1/8 (.09)
Full Load Amps (FLA) 9.5 19
Operating Speed High/
Low (RPM) 4200
1850
Bearing Lubrication Factory Lubricated
(additional grease not required)

1--8
T--304 04/08
b. Condenser Fan Motor
Condenser Motor Permanent Magnet
24 VDC 12 VDC
Horsepower (kW) 1/8 (.09)
Full Load Amps (FLA) 918
Operating Speed
(RPM) 2950
Bearing Lubrication Factory Lubricated
(additional grease not required)
c. Temperature Sensors (Return Air Sensor)
Input Range: --52.6 to 158°F (--47 to 70°C)
Output: NTC 10K ohms at 77°F(25°C)
d. Ambient Sensor (Optional)
Opens at: 25°F(10°C)
Closes at: 35°F(1.7°C)
1.5 SAFETY DEVICES
System components are protected from damage
caused by unsafe operating conditions with safety
devices. Safety devices with Carrier Transport Air
Conditioning supplied equipment include high pressure
switch (HPS), low pressure switch (LPS), circuit
breakers and fuses.
a. Pressure Switches
High Pressure Switch (HPS)
During the air conditioning cycle, compressor clutch
operation will automatically stop if the HPS switch
contacts open due to an unsafe operating condition.
Opening HPS contacts de-energizes the compressor
clutchshuttingdownthecompressor.Thehighpressure
switch (HPS) is installed at the compressor assembly
(05G, 05K & TM--31).
Low Pressure Switch (LPS)
The low pressure switch is installed close to the
compressor and openson a pressure dropto shut down
the system when a low pressure condition occurs. The
lowpressureswitchisinstalledatthecompressor(05G,
05K & TM--31).
NOTE
Ondual loopsystems that usetheA--6, TM--21
& some TM31’s, the pressure switches are not
located on the compressors. They are installed
in--line.
b. Fuses and Circuit Breakers
The RelayBoardis protectedagainst high current by an
OEM supplied circuit breaker or fuse located in the bus
battery compartment (150 Amp for 12 VDC & 125 Amp
for 24 VDC systems). Independent 15 Amp, 24 VDC or
20 Amp, 12 VDC fuses protect each motor while the
output circuits are protected by an additional 5 Amp
circuit breaker. During a high current condition, the fuse
may open.
1.6 AIR CONDITIONING REFRIGERATION
CYCLE
When air conditioning (cooling) is selected by the
controller, the unit operates as a vapor compression
system using R-134a as a refrigerant (See Figure 1--6
Dual Loop & Figure 1--8 Single Loop flow diagrams).
The main components of the system are the A/C
compressor, air-cooled condenser coils, receiver,
filter-drier, thermostatic expansion valve, liquid line
solenoid valve and evaporator coils.
The compressor raises the pressure and the
temperature of the refrigerant and forces it into the
condenser tubes. The condenser fan circulates
surroundingair(whichisatatemperaturelowerthanthe
refrigerant) over the outside of the condenser tubes.
Heat transfer is established from the refrigerant (inside
the tubes) to the condenser air (flowing over the tubes).
The condenser tubes have fins designed to improve the
transfer of heat from the refrigerant gas to the air; this
removal of heat causes the refrigerant to liquefy, thus
liquid refrigerant leaves the condenser and flows to the
receiver.
The refrigerant leaves the receiver and passes through
the receiver outlet/service valve, through a filter-drier
where a descecant keeps the refrigerant clean and dry.
From the filter-drier, the liquid refrigerant then flows
through the liquid line solenoid valve to the sight--glass
and then to the thermostatic expansion valve. The
thermal expansion valve reduce pressure and
temperature of the liquid and meters the flow of liquid
refrigerant to the evaporator to obtain maximum use of
the evaporator heat transfer surface.
The low pressure, low temperature liquid that flows into
the evaporator tubes is colder than the air that is
circulated over the evaporator tubes by the evaporator
fans (fans). Heat transfer is established from the
evaporator air (flowing over the tubes) to the refrigerant
(flowing inside the tubes). The evaporator tubes have
aluminum fins to increase heat transfer from the air to
the refrigerant; therefore the cooler air is circulated to
the interior of the bus. Liquid line solenoid valve closes
during shutdown to prevent refrigerant flow.
The transfer of heat from the air to the low temperature
liquid refrigerant in the evaporator causes the liquid to
vaporize. This low temperature, low pressure vapor
passes through the suction line and returns to the
compressor where the cycle repeats.
1.7 HEATING CYCLE
Heating circuit (See Figure 1--7) components furnished
byCarrier TransportAirConditioningincludetheheater
cores and solenoid operated heat valves. Components
furnished by the bus manufacturer may include a water
temperature switch (WTS) and boost water pump.
The controller automatically controls the heat valves
during the heating mode to maintain required
temperatures inside the bus. Engine coolant (glycol
solution) is circulated through the heating circuit by the
engine and an auxiliary boost water pump. When the
heat valve solenoids are energized, the valves willopen
to allow engine coolant to flow through the heater coils.
The valves are normally closed so that if a failure
occurs, the system will be able to cool.

1--9 T--304
04/08
41
Driver’s
Evaporator
1
2
3
4
56
7
9
10
11
12
3
8
9
1 Thermal Expansion Valve
2 Liquid Line Sight Glass
3 Service Port
4 Liquid Line Solenoid
5 Evaporator Coil
6 Heat Coil
7 Subcooler
8 Compressor (TM--21 or A--6)
9 Service Valve
10 Condenser Coil
11 Filter--Drier
12 Receiver
Note: Items 1 through 12 are typical, both systems.
Figure 1--6 Refrigerant Flow Diagram -- Cooling (Dual Loop)

1--10
T--304 04/08
SUPPLY
RETURN
11
2
3
4
4*
*
1. Heat Coil
2. Vehicle Radiator
3. Boost Pump
4. Heat Solenoid Valve
*Optional Hand Valve
Figure 1--7 Flow Diagram -- Heating
NOTE: Inorderto ensurewaterisenteringtheheatercoilssufficientlyheated,itissuggestedthat
theOEMsuppliedWaterTemperatureSwitch(WTS)closeontemperatureriseat150°F(65.5°C).

1--11 T--304
04/08
EVAPORATOR
CONDENSER
Relief Valve
Dash Air
Liquid Line
Discharge
Liquid
Suction
Coolant
Dash Air
Suction Line
1
2
5
6
7
8
9
10
11
9
8
6
5
Discharge Check Valve
3
3
4
4
4
Figure 1--8 Refrigerant Flow Diagram, Cooling (Single Loop) AC350
1. Thermal Expansion Valve
2. Liquid Line Sight Glass
3. Service Port R134a
4 Service Port 1/4 Flare (Acme)
5. Liquid Line Solenoid
6. Evaporator Coil
7. Compressor
8. Service Valve
9. Condenser Coil
10. Filter--Drier
11. Receiver

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T--304 04/08
K14M K12M K11M K10M K9M K8M K7M K6M K5M K4M K3M K2M K1M
V1
V2
V3
V4
V5
K13M K4A K3A K2A K1A
F1A
F2A
F3A
F4A
F1M
F2M
F3M
F4M
F5M
F6M
F7M
F8M
F13M
F14M
F15M
F16M
frei
frei
frei
A1P
frei
B1N
13456
7
8
9
2
10
11
12
1314151617
18
19
20
21
22 23
24
25
26 27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
K15M
SeeFigure1--9Sheet2Legend
CLR1 CLR2
47 48
Ref. Sutrac 60--01--21--062
Ref. Sutrak Schematic 65--01--28--056--01--3
Figure 1--9 Sheet 1 -- Electrical Control Board (280P)