booklet on roof mounted package unit of lhb ac coaches

MINISTRY OF RAILWAYS
Booklet on
CAMTECH/E/2020-21/EP-06/RMPU-LHB/1.0
ii
Booklet
on
of LHB AC Coaches
“We at RDSO, Lucknow are committed to maintain and update
transparent standards of services to develop safe, modern and cost
effective railway technology complying with statutory and regulatory
requirements, through excellence in research, designs and standards
by setting quality objectives, commitment to satisfy applicable
requirements and continual improvements of the quality
management system to cater to growing needs, demand and
expectations of passenger and freight traffic on the railways through
periodic review of quality management systems to achieve continual
improvement and customer appreciation. It is communicated and
applied within the organization and making it available to all the
relevant interested parties.”
iv
FOREWORD
Air conditioning of the Railway Coaches is a priority requirement for passenger comfort
and to provide a comfortable environment inside the coach for passengers travelling in a train.
In LHB coaches, air conditioning i.e. supply of clean fresh air at a controlled uniform
temperature is achieved by provision of two Roof Mounted Package Units (RMPU) in each
coach. The proper upkeep and maintenance of these units is essential to ensure proper working
during the journey of the train.
To ensure wide dissemination of knowledge on Roof Mounted Package Units of LHB
Coaches, CAMTECH, Gwalior has prepared this booklet. This booklet comprises brief on
technical and constructional features, functional description, working of RMPU and its
Microprocessor Controller, maintenance activities etc.
I am sure that this booklet will be useful for field maintenance staff of coaching stock in
their day to day working and improving the reliability and safety of coaching stock on Indian
Railways.
v
PREFACE
Air-conditioning of railway coaches is a priority passenger amenity for the maximum
comfort and well-being of passengers in a railway travel. Microprocessor controlled, two air
conditioning package units (RMPUs) are provided on roof of each LHB coach and they are
controlled by single microcomputer based controller. These air conditioning units work in fully
automatic mode. Depending on ambient temperature, available modes of heating, ventilating,
cooling and dehumidifying are selected and controlled.
These units can work satisfactorily on End On Generation (EOG) and Head On
Generation (HOG) type AC coaches. The generator car is provided only with one air
conditioning unit. Each RMPU comprises two distinct refrigeration circuits i.e. two compressors,
two condensers, two cooling coils, one heater etc. The RMPU of LHB coaches has various
features like thermal switch protection for motors, pressure transducers for LP/ HP
measurement, NTC type temperature sensors, humidity control through Hygrostat,
Connections through Harting connectors (Plug & Socket) etc.
Booklet on “Roof Mounted Package Unit (RMPU) of LHB AC Coaches” has been prepared
by CAMTECH, Gwalior with the objective to disseminate the knowledge. This booklet comprises
the details of RMPU and microprocessor Controller Unit along with functional details and
maintenance practices. This booklet also comprises the basic terminology used in heating,
ventilation and air conditioning (HVAC). This will be useful for electrical coaching maintenance
staff over Indian Railways.
It is clarified that this booklet does not supersede any existing provisions laid down by
Railway Board/ RDSO, OEMs. This booklet is for guidance only and it is not a statutory
document.
I am sincerely thankful to Shri B. C. Agrawal, SSE/EL/CAMTECH, Smt. Sangeeta
Shrivastava, JE/IT/CAMTECH, and all field personnel who helped us in preparing this handbook.
Technological up-gradation & learning is a continuous process. Please feel free to write us for
any suggestion/ addition/ modification in this booklet.
CAMTECH, Gwalior Himanshu Maheshwari
vi
CONTENTS
DISCLAIMER ................................................................................................................................................... x
1. INTRODUCTION ...................................................................................................................................1
3. BASIC REQUIREMENTS FOR COACH AIRCONDITIONING SYSTEM .......................................................2
4. SALIENT FEATURES OF RMPU FITTED ON LHB AC COACHES ..............................................................2
5. TRANSPORT AND STORAGE ................................................................................................................3
7. DETAILS OF AIR CONDITIONING SYSTEM IN LHB AC COACH ..............................................................5
7.1. Compact Air Conditioning Unit (RMPU) ..............................................................................5
7.1.1. Compressors ........................................................................................................................6
7.1.5. Heating Assembly ................................................................................................................9
7.1.10. Protections ........................................................................................................................ 11
7.1.11. Other Components, Control and Safety Devices of RMPU ............................................... 12
7.1.12. Fresh Air Screens .............................................................................................................. 13
8. ELECTRICAL CONTROL PANELS ......................................................................................................... 13
9. Microprocessor Based Controller for RMPU .................................................................................... 14
9.1. LAYOUT OF LEDS IN MICROPROCESSOR CONTROL UNIT ...................................................... 17
9.2. Microprocessor Control Panel ............................................................................................... 19
vii
10. FUNCTIONS AND MODES OF OPERATION OF RMPU ....................................................................... 20
10.1. Pre-Heating Mode .................................................................................................................. 21
10.2. Pre-Cooling Mode .................................................................................................................. 21
10.4. Cooling Mode ......................................................................................................................... 21
10.5. Heating Mode ........................................................................................................................ 22
10.6. De-Humidification .................................................................................................................. 23
10.8. Manual mode ......................................................................................................................... 23
10.10. Other Functions of Controller ................................................................................................ 24
11. PROTECTION DEVICES (MCBs AND FUSES) ...................................................................................... 24
12. CONTACTORS & RELAYS ................................................................................................................... 25
CHAPTER 2 MAINTENANCE ............................................................................................................. 28
2.2. Compressors ............................................................................................................................ 31
2.4. Return/ Fresh Air Filters .......................................................................................................... 33
2.5. HP/ LP/ OHP Cutout Switch ..................................................................................................... 34
2.6. Heater ...................................................................................................................................... 34
2.9. Evaporator Coil ........................................................................................................................ 35
2.11. Access Doors .......................................................................................................................... 36
2.12. Drip Tray ................................................................................................................................. 36
REFERENCES ............................................................................................................................................... 48
LIST OF FIGURES
Figure 1: LHB Coach fitted with RMPUs at both ends ................................................................. 1
Figure 2: Compact air conditioning unit (RMPU) ........................................................................ 6
Figure 3: Major Sections of RMPU .............................................................................................. 6
Figure 4: Compressors in RMPU .................................................................................................. 7
Figure 5: Axle fans (Condenser Fans) along with motors in RMPU ............................................. 7
Figure 6: Condenser units in RMPU............................................................................................. 8
Figure 7: Evaporators units in RMPU .......................................................................................... 8
Figure 8: Twin-sucking radial fans for the supply air in RMPU ................................................... 9
Figure 9: Heating Unit in RMPU .................................................................................................. 9
Figure 10: pressure transducers (pressure switches) ................................................................. 10
Figure 11: Humidity sensor ......................................................................................................... 10
Figure 12: NTC type temperature sensor .................................................................................... 11
Figure 13: HP/ LP Cut Out (Cartridge type) ................................................................................. 11
Figure 14: Overheat protector (Bimetallic type thermal switch) ................................................ 12
Figure 15: Fresh Air Screens ........................................................................................................ 13
Figure 16: Control Panel for RMPU ............................................................................................. 13
Figure 17: Switch Board Cabinet ................................................................................................. 14
Figure 18: Block diagram of Control System of RMPU ................................................................ 15
Figure 20: Microprocessor Based Controller for RMPU .............................................................. 16
Figure 21: Operation Panel for Air Condition System ................................................................. 19
ix
ISSUE OF CORRECTION SLIP
The correction slips to be issued in future for this handbook will be numbered as follows:
CAMTECH/ E/EP-06/2020-21/RMPU/1.0/C.S. # XX date---
Where “XX” is the serial number of the concerned correction slip (starting from
01 onwards).
CORRECTION SLIPS ISSUED
Sr. No. Date of Issue Page no. & Item no. modified Remarks
x
DISCLAIMER
It is clarified that the information given in this booklet does not
supersede any existing provisions laid down by the Railway Board, RDSO
and OEM’s Manual. This document is not statuary and instructions
given are for the purpose of guidance only. If at any point contradiction
is observed, then Railway Board/RDSO guidelines and OEM’s
Maintenance and Operating Manuals may be referred.
OUR OBJECTIVE
improvement in productivity and performance of all Railway assets
and manpower which inter-alia would cover reliability, availability,
utilization and efficiency.
If you have any suggestion & any specific comment, please write to us: Contact person: Dy. Director (Electrical) Postal Address: Centre for Advanced Maintenance Technology,
Opposite Hotel Adityaz, Near DD Nagar, Maharajpur, Gwalior (M.P.) Pin Code – 474 005
Phone: 0751 - 2470740 Fax: 0751 – 2470841 E-mail: [email protected]
xi
CB Circuit Breaker
CP Control Pressure
FA Fresh Air
HOG Head On Generating
ICF Integral Coach Factory
IOH Intermediate Overhaul
IR Indian Railways
IS Indian Standards
IV Inter Vehicular
kg Kilogram
MCB Miniature Circuit Breaker
MCS Mode Control Switch (Rotary Switch On The AC Control Panel)
MPCB Motor Protection Circuit Breaker
NTC Negative Temperature Coefficient
OHP Overheat Protector (Thermal Switch In Supply Air Opening To Prevent Overheating)
PC Personal Computer
POH Periodic Overhauling
RH Relative Humidity
RMPU Roof Mounted Package Unit (= Roof Mounted Air Conditioner)
RPM Revolution Per Minute
TL Train Lighting
U Coefficient Of Heat Transfer For Window Due To Solar Heat Gain
UPF Unity Power Factor
USB Universal Serial Bus
CAMTECH/E/EP-06 /2020-21/RMPU/1.0 1
Booklet on Roof Mounted Package Unit (RMPU of LHB AC Coaches March, 2021
CHAPTER 1
GENERAL DESCRIPTION
1. INTRODUCTION
Microprocessor controlled, two air conditioning package units (RMPUs) are provided on roof of each LHB coach (2 tier, 3 tier & chair car) at the both ends. Both air conditioning package units are controlled by single microcomputer based controller, mounted in switch board cabinet and fed from battery net. These air conditioning units work in fully automatic mode. Depending on ambient temperature, available modes of heating, ventilating, cooling and dehumidifying are selected and controlled. These units can work satisfactorily on Self Generating (SG), End On Generation (EOG) and Head On Generation (HOG) type AC coaches. The total cooling capacity of each LHB coach is 14.0 TR (2x22.5 kW) fitted with two nos. RMPU units of 7.0 TR. each. The generator car is provided only with one air conditioning unit. The units used in the different coaches of LHB variant are identical except in double decker LHB chair cars. In double decker LHB chair car two units of 10 TR each are provided at both ends.
Figure 1: LHB Coach fitted with RMPUs at both ends In EOG and HOG coaches, power supply to these units are fed from 60 kVA step down transformers, stepping down 750 V, 3 Φ AC, 4 wire, 50 Hz supply to 415 V, 3 Φ AC, 4 wire, 50 Hz supply. The 750V supply is fed to entire rake through two feeders running on both sides of coaches along the full length of rake. This supply is either fed by power cars or hotel load converters fitted on electric locomotives. Air conditioned air is supplied via perforated ceiling in the passenger room, air conditioning of entrance areas, toilets and pantry with return air. The 7.0 TR RMPU for LHB coaches are being manufactured as RRDSO specification no. RDSO/PE/SPEC/AC/0061-2005 (Rev.-1), December 2011. The RMPU is as per RDSO
drawing no. RDSO/PE/SK/AC/0069-2004 (Rev.-1). The Microprocessor Controller of RMPU for LHB coaches and double decker coaches are being manufactured as per RDSO specification no. RDSO/PE/SPEC/AC/0139-2009 (rev.-1), December, 2011. The general functions of AC system for all type of coaches and generator cars are:
Ventilation
2. WHY AIR CONDITIONING IN RAILWAY COACHES IS REQUIRED
Passengers during railway travel are adversely affected by infiltration of air unpleasantly laden with dust due to open windows. This is more in case of high speed passenger carrying trains.
Secondly for a tropical country like India, the temperature varies from 48-degree C during summer to 2-degree C during winter.
Air-conditioning of railway coaches is, therefore, necessary for the maximum comfort and well-being of passengers in a railway travel.
In keeping passenger comfort on priority, air conditioning of coaches for passengers is being done by the Indian Railways.
3. BASIC REQUIREMENTS FOR COACH AIRCONDITIONING SYSTEM
Supply of clean fresh air at a controlled uniform temperature in the coach.
Providing, within the confines of the Railway carriages to the continuously changing number of on-board passengers.
Provision for heating as well as cooling on a train that travels through areas of widely differing climate during its journey round the year.
Operation of the air conditioning equipment from self-generated power (Self generating coaches), power from power cars (EOG coaches), power from locomotives (HOG coaches) and controlled on the train.
Securing sufficient air movement throughout the various section of the railway coaches.
4. SALIENT FEATURES OF RMPU FITTED ON LHB AC COACHES
Micro-Controller based AC Package unit. Control and regulation function of air conditioning system (two nos. RMPU) are performed by single Microprocessor controller unit with software installed in it.
The refrigeration system comprises two distinct refrigeration circuits i.e. two compressors, two condensers, two cooling coils, one heater etc.
Servo-Motor Controlled Fresh Air Damper for automatic Pre-cooling / Pre-heating.
Micro-Processor Control (with RS 232 Port) with fault Diagnostics and Data acquisition system.
Motors protected with Thermal switches.
Pressure transducers for LP/ HP measurement
NTC type temperature sensor
Humidity Control through Hygrostat.
Compressor- hermetically sealed scroll type.
Automatic temperature setting based on ambient temperature sensor and switch over to Pre-cooling /Pre- Heating mode.
Improved air duct design for better air flow and cooling.
Connections through Harting connectors (plug & socket)
Evaporator unit water tight
Suck through type arrangement
Power supply- 415 +/-5% V , 3 ph, 50 Hz+- 3%
Control supply 110V ac, Single phase
Capacity with one condenser- 75%
5. TRANSPORT AND STORAGE
For ease of transportation, the air conditioner is mounted on a transport frame. It is recommended not to unpack and remove the air conditioner from the transport frame until it is to be installed on the coach roof.
When the transport frame is not used, make sure the air conditioner is supported under its mounting brackets and a gap remains under air conditioner in order to avoid damages to the enclosure and the air interfaces.
Do not place the air conditioner on the floor.
The air conditioner must be stored in a weather protected space. Do not store the air conditioner in the open. While in storage, all openings must be kept sealed to prevent the ingress of rain water, dust, insects and rodents.
6. TECHNICAL DATA (PER UNIT)
S.No. Description Details
2. Cooling Capacity 7.0 TR
3. Heating capacity 6.0 kW
4. Compressor capacity 3.5 TR (two nos.)
5. Maximum power consumption 16.5 kVA
6. Supply Voltage 415 V, 3 Ø, AC, 50 Hz
7. Operating voltage 415 V, 3 Ø, AC, 50 Hz
8. Control Voltage 110 ± 30% V DC
9. Fan motor axial (for condenser) 1HP, 415V, 3 Ø
10. Fan motor radial (for evaporator) 1.5HP, 415V, 3 Ø
11. Fresh air supply (m3/hr) 820 m3/h
12. Supply air flow 4000 m3/h±10%
13. Condenser Fan 0.75 kW, 415 V, 3 Ø, AC, 50 Hz, 1400 RPM (two nos.)
14. Supply air fan (Blower Motor) 1.1 kW, 415 V, 3 Ø, AC, 50 Hz, 1400 RPM (one no.)
15. Refrigerant R 407C
16. Weight (kg) 630 Approx.
17. Dimensions (mm) L x W x H 2220 x 2200 x 500
18. Material of enclosure Stainless steel (unpainted)
Safety Devices Provided in the RMPU
Equipment Protection Specifications Remark
Condenser fan motor 1 Temperature switch above 130 degree C
Condenser fan motor 2 Temperature switch above 130 degree C
Supply air fan Temperature switch above 130 degree C
Electric heater Thermostat (Over heat protection or OHP)
Beyond 65 degree C due to any reason
If OHP not acted then at 85 degree C,
disconnection by microprocessor by opening respective contactor
Fusible link (ESTI) at 130 degree C by bursting the bulb & permanent disconnection of supply
Pressure switch / -sensor
High pressure switch
Range 30-23 bar,
Low pressure switch
Range 20-16 bar
The AC package unit can work satisfactorily under following conditions:
Summer condition Dry Bulb Wet Bulb % R. H.
Outside (Dry summer) 50 degree C 25 degree C --
Outside (Wet summer) 40 degree C 28 degree C --
Inside (dry and wet) 20 to 25 degree C 60-40%
Winter Conditions
7. DETAILS OF AIR CONDITIONING SYSTEM IN LHB AC COACH
The AC system for the LHB coaches consists of the following assemblies:
Compact air conditioning unit
Duct system
Exhaust air system (Exhaust air unit, WC/WC exhaust fan, WC/ Switch cabinet exhaust fan)
Circulating air duct system
Sensors
7.1. Compact Air Conditioning Unit (RMPU) Each compact air conditioning unit (RMPU) has two separate cooling circuits consisting of the following major components:
Two hermetic sealed scroll compressors.
Two condensers with Cu pipes and pre coated Aluminium fins.
Two axel fans (condenser fans) with motors for cooling the condensers.
Two evaporators (cooling units)
Two twin-sucking radial fans for the supply air (driven by the Evaporator blower motor)
Three maintenance covers
Control and safety devices
Figure 2: Compact air conditioning unit (RMPU)
Figure 3: Major Sections of RMPU
7.1.1. Compressors
Two hermetic sealed scroll compressors along with Cu pipe lines are provided for two cooling circuits in each RMPU. They are fixed with anti-vibration mounting pads for reliable operation. Each compressor of minimum 3.5 TR capacity at 60 Degree C condensing and 5 Degree C evaporating temperature, making total rating of AC package unit 7 TR.
Figure 4: Compressors in RMPU
7.1.2. Condensers and Condenser Fans
Two Condensers with Cu tubes and pre coated Aluminium fins are provided for two cooling circuits in each RMPU. These are air cooled and two axle fan (condenser fans) along with motors are also provided in each unit for the cooling of the condenser fins. They are fixed with anti-vibration mounting pads for reliable operation.
Figure 5: Axle fans (Condenser Fans) along with motors in RMPU
Figure 6: Condenser units in RMPU
7.1.3. Evaporators (cooling unit)
Two evaporators units with Cu pipes and pre coated Aluminium fins are provided for two cooling circuits in each RMPU.
Figure 7: Evaporators units in RMPU
7.1.4. Supply Air Fan and Blower Motor Two twin-sucking radial fans for the supply air (driven by single Evaporator blower motor) are also provided in each unit for the supply of cooling air.
Figure 8: Twin-sucking radial fans for the supply air in RMPU
7.1.5. Heating Assembly
Each RMPU also has one three phase stainless steel heater element (one set) without fins of 6 kW capacity. The heating coil is supplied with 415V-3~50Hz supply. Heater has following protections:
1. Over heat protection switch for heater One
2. ESTI-1 cartridge + 130 degree C for ultimate disconnection of power supply
One
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7.1.6. Pressure Transducers
Following pressure transducers (pressure switches) are provided in RMPU for the protection and indication of various pressure (LP, HP) parameters while working of RMPU. They ensure safe and reliable working of RMPU.
1. Pressure switch 23/20 bar Two
2. Pressure switch 23/20 bar Two
3. Pressure switch 0-40 bar Two
Figure 10: pressure transducers (pressure switches)
7.1.7. Air Filters
Following air filters are provided in RMPU for the filtration of air at various locations while working of RMPU. They ensure clean air supply. Material is progressively structured, non – woven break resistant, thermally bonded fire retardant synthetic material.
1. Fresh air filters Two
2. Mixed (supply) air filters Two
3. Return air filters Two
7.1.8. Humidity Control
Relative humidity is controlled inside coach by RMPU and is monitored by one Hygrostat (Range: 30-100% RH) located at return air duct. It restricts the relative humidity level inside the air conditioning compartment to a maximum of 60 % under any circumstances. Desired temperature is achieved by switching on heaters (50%) as per logic, such that the combined power consumption does not exceed the permissible power under cooling capacity.
Figure 11: Humidity sensor
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7.1.9. NTC type sensors
Three NTC type temperature sensors for each RMPU (total 06 nos. per coach) are provided to control the temperature inside the LHB AC coach. The location of temperature sensors are 1 Return Air, 1 supply air, 1 Air duct in one RMPU.
Figure 12: NTC type temperature sensor The following temperature settings can be maintained inside the air conditioned compartment by means of seven positions of the stepped rotary switch provided on the Switch Board Cabinet.
7.1.10. Protections
LP, HP cut outs have been provided in the refrigerant circuit for protection in case of low pressure and high pressure respectively.
Figure 13: HP/ LP Cut Out (Cartridge type)
Position of the Rotary switch
Temperature
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Overheat protector (Bimetallic type thermal switch) has been provided in the heater circuit.
Figure 14: Overheat protector (Bimetallic type thermal switch)
ESTI protection has been provided in the heater circuit to operate at 130°C in case of failure of overheat protector for ultimate disconnection of power supply to heater.
Individual electrical protection has been provided by MCB’s.
In-built overheat protection has also been provided in the motors windings, which are interlocked with microprocessor.
7.1.11. Other Components, Control and Safety Devices of RMPU
Following other components are also provided for control and safe working of RMPU.
S. No. Components Quantity per unit
1. Filter dryer Two
3. Solenoid valve Two
Two
9. Anti-vibration mounting pads for whole unit Six
10. Anti-vibration mounting for compressors as required
11. Anti-vibration mounting for condensers motors as required
12. Stainless steel drip trays complete with arrangement for drainage of condensate water
Two
14. Power & control connectors (M/F) along with accessories
one for power and one for control supply
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7.1.12. Fresh Air Screens
In each coach/ generator car four air screens are installed at the coach ends parallel to the air conditioning unit. These screens are fitted with exchangeable air filters.
Figure 15: Fresh Air Screens
8. ELECTRICAL CONTROL PANELS
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Figure 17: Switch Board Cabinet
9. Microprocessor Based Controller for RMPU
The control and regulation of both RMPUs is performed by one microprocessor controller, which is located in switch board cabinet and fed from battery net. This is designed as per RDSO specification no. RDSO/PE/SPEC/AC/0139- 2009 (Rev.1) effective from December, 2011.
The salient features of microprocessor based controller are given below:
It is a fully automated control and monitoring system for all capacity RMPU units.
CAMTECH/E/EP-06 /2020-21/RMPU/1.0 15
The controller has fault diagnostic facility for continuous storage of various electrical faults in the system, in time sequence manner.
The fault data can be downloaded from the controller for analysis purpose.
This unit works on 110 ± 30% V DC/AC.
A Real Time Clock (RTC) is provided to determine the date and time at which the fault has occurred.
Controller read the position of the Set Point Generator (7 positions) installed inside.
Figure 18: Block diagram of Control System of RMPU
There are (8) Analog inputs designated X402 & X403. Of these eight inputs, 6 nos. are temperature sensors (NTC type) and there is 1 no. of humidity sensor for measuring humidity level. 1 no. of set point generator for temperature adjustment inside the coach.
There are (20) digital inputs designated as X701 & X702.
The external voltage is + 110V, Digital input returns must be tied to an external return (Input common).
There are 20 Digital Outputs designated as X301, X302, X501 and X502.
Digital outputs are externally sourced solid-state switches.
Digital outputs are groups into four: each group requires one output common.
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Figure 19: Microprocessor Based Controller for RMPU
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9.1. LAYOUT OF LEDS IN MICROPROCESSOR CONTROL UNIT
Meaning of the individual displays and consequences for the operation of the conditioning system:
Lamp no. Meaning of Display
Lamp no. Meaning of Display SID/
Liebherr LHB/ LEEL
K-119 011 Glows for fault in AC system
K-116 02 Glows when Fresh/ Recirculating Air flap is set at Recirculating Air
K-117 012 Glows when Fresh/ Recirculating Air flap is set at Fresh Air
K-113 03 Glows when Ventilation-I is ON
K-114 013 Glows when Ventilation-II is ON
K-21 04 This indication is not for AC system
K-115 014 Glows when Ventilation-II is ON
K107 05 Glows during cooling operation indicates bypass cooling in Unit-I
K-108 015 Glows during cooling operation indicates bypass cooling in Unit-II
K-109 06
Glows during cooling operation indicates pressure switch functional when CD 1.1 in Unit-I starts.
K-111 016
Glows during cooling operation indicates pressure switch functional when CD 2.1 in Unit-II starts.
K-110 07
K-112 017
K-101 08 Glows during cooling operation indicates Comp 1.1 ON
K-105 010 Glows during Heating operation indicates Heater-I, Unit-I ON
K-106 020 Glows during Heating operation indicates Heater-II, Unit-II ON
K-15 I1 Glows when AC system gets ON with switch S1U4S1
K-16 I11 Glows when 415V is OK
K-1 I2
Glows when winding temperature of CD 1.1 motor is within limit. This light goes OFF when winding temperature goes beyond limit & the motor also switches OFF.
K-3 I12
Glows when winding temperature of CD 2.1 motor is within limit. This light goes OFF when winding temperature goes beyond limit & the
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motor also switches OFF.
K-2 I3
K-4 I13
K-13 I4
This is OFF when winding temperature of Ventilation-I motor is within limit. This light Glows when winding temperature goes beyond limit & the AC Unit-I also goes out of service.
K-14 I14
This is OFF when winding temperature of Ventilation-II motor is within limit. This light Glows when winding temperature goes beyond limit & the AC Unit-II also goes out of service.
K-17 I5
Glows when temperature of Heater-I, Unit-I is within limit. This light goes OFF when Heater temperature goes beyond limit & the Heater also switches OFF.
K-18 I15
Glows when temperature of Heater- II, Unit-II is within limit. This light goes OFF when Heater temperature goes beyond limit & the Heater also switches OFF.
K-6 I6
Glows when LP is OK. This light goes OFF when pressure at LP switch of refrigerant circuit 1.1 goes down and switches off refrigerant circuit 1.1 if the pressure remains low for more then 30 seconds.
K-10 I16
K-8 I7
K-12 I17
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K-19 I8
Glows when Control pressure switch-1 is ON, which means HP is more then 25 bar which will automatically run second condenser motor.
K-20 I18
Glows when Control pressure switch-2 is ON, which means HP is more then 25 bar which will automatically run second condenser motor.
K-5 I9
This will Glow when HP gets more then setting of HP cut out switch 1.1 and the compressor 1.1, Unit-I will get OFF
K-9 I19
This will Glow when HP gets more then setting of HP cut out switch 2.1 and the compressor 2.1, Unit-II will get OFF
K-7 I10
K-11 I20
9.2. Microprocessor Control Panel
The control panel for RMPU is provided with LCD display and it works on 110 V dc ± 30%. It is installed in switch board cabinet. There is a rotary switch on switch panel for putting the unit in manual mode in case of emergency.
One display unit (as shown below) for each control unit is mounted on the left door of the control panel. The control display-unit functions as an interface between operator and system. Display unit have necessary keys for the purpose.
Figure 20: Operation Panel for Air Condition System
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The following functions are possible through key board.
• Setting of time, date, train no. and RMPU no.
• Clearing of the fault on display.
• Viewing of the stored faults.
• Display of digital inputs and outputs.
• Display of status of the system.
• Setting various parameters for controller by maintenance staff.
9.3. Fault Storage/ Self Diagnostic System
• A fault storage system records various tripping and faults of the RMPU along with the instant status of various parameters like temperature setting, LP & HP pressure and relative humidity.
• The fault messages along with trouble shooting instructions are displayed during various fault conditions.
• The system monitors supply voltage and current and records the power consumption of units.
10. FUNCTIONS AND MODES OF OPERATION OF RMPU
The outside air (fresh air) is sucked in via the two fresh air screens and their air filters on the carriage side wall. It is mixed in the unit with the outside air/ recirculating air ratio can be set by means of air dampers, the positions of which are controlled by the controller of the air conditioning system.
The temperature inside the coach is maintained as per the temperature setting selected by the operator. It is possible to alter the assigned value of temperature (in step of 0.1° C.) through key-board on display unit.
The difference between cut in and cut out temperature shall be 2°C. The difference of 2°C reduces the duty cycle of compressor & eventually the failures of compressors.
Fault storage/diagnostics system: Faults are recorded automatically. Faults can be downloaded by Laptop. Display Unit is available. Trouble shooting instructions are displayed on the screen.
The heater is cycled with a period of 60 seconds The ON period of the heater is controlled by a control signal of the computer.
System monitors supply voltage and current and record the power consumption.
The Heating, Ventilation and Air Conditioning unit work in different modes depending upon the temperatures SENSORS & Humidity level. The following are the main modes of operation:
i. Pre-Heating Mode
ii. Pre-Cooling Mode
iv. Cooling Mode
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v. Heating Mode
vi. Dehumidification mode
viii. Manual Mode
10.1. Pre-Heating Mode
If the Ambient Temperature & Room Temperature is less than 14-degree C, the controller decides to operate in Pre- Heating mode.
In this mode the fresh air/re-circulating air flap set to 100% re-circulation air and exhaust fans are turned off.
Heaters are operated at its maximum duty cycle (55 seconds ON and 5 seconds OFF)
This cycle runs for 30 minutes, after that depending on temperature, mode changed to Cooling/Heating.
10.2. Pre-Cooling Mode
If the Ambient Temperature & Room Temperature is greater than 28-degree C, the controller decides to operate in Pre-cooling mode.
In this mode the fresh air/re-circulating air flap set to 100% re-circulation air and exhaust fans are turned off.
Both Compressor are turned ON for maximum Cooling.
This cycle runs for 30 minutes, after that depending on temperature, mode changed to Cooling / Heating.
10.3. Normal Operation Mode
Depending on the Ambient Temperature, controller selects Heating or Cooling mode.
If the Ambient Temperature is less than the SET temperature, then Heating mode is selected. Ex: SET=20-degree C, AT= 18-degree C, HGS = Normal
If the Ambient Temperature is greater than SET Temperature, then Cooling mode is selected. Ex: Ex: SET= 20-degree C, AT= 23-degree C, HGS = Normal
During Heating mode or Cooling mode, when the Humidity sensor gives a High level, the systems enters De-humidification mode. Ex: SET= 20-degree C, AT= 23- degree C , HGS = HIGH
10.4. Cooling Mode
During Cooling mode, the controller selects depending on the difference in temperature between SET temperature and Room Temperature.
If the difference in temperature is less than 5-degree C and greater than 2-degree C, Condenser & one compressor turns ON.
If the difference in temperature is greater than 5-degree C, Condenser with both compressors ON.
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10.4.1. Temperature Regulation in Cooling Mode
Cooling
If (RT-SET) is -Ve value Cooling step sleep, only Ventilation & Exhaust ON
Ex: RT=19°C, SET=20.0°C & AT >18°C.
Step-1
If (RT-SET)<=1, is single condenser and Compressor ON.
Ex: SET=20°C, RT=20 to 21°C and AT>20°C.
Cooling Exit (shutdown)
Ex: SET=20°C, RT<=19°C and AT>20°C. Step-2:
Cooling Entry:
If (RT-SET) = (1 to 2°C) single condenser and compressor without BYPASS.
Ex: SET=20°C, RT=(21 to 22°C.) AT>20°C
Cooling Exit:(Shutdown)
Ex: SET=20°C, RT<=19°C and AT>20°C.
10.5. Heating Mode
During Heating mode, the controller selects depending on difference in temperature between SET temperature and Room Temperature for one of the 3 Heating cycle duty cycles:
• Minimum duty cycle - 5 sec ON & 55 sec OFF.
• Medium duty cycle - 30 sec ON & 30 sec OFF.
• Maximum duty cycle - 55 sec ON & 5 sec OFF.
10.5.1. Temperature Regulation in Heating Mode
Heating
If (SET-RT) is -Ve value, Heating step sleep mode, only Ventilation & Exhaust Fan ON
Ex: RT=20°C, SET=19.0°C & AT <22°C.
Step-1
Heating Entry:
If (SET-RT)<=1°C, Minimum duty cycle Heater ON for 5 sec and OFF for 55 sec.
Ex: SET=19°C, RT= (17 to 18 °C) and AT<19°C.
Heating Exit (shutdown)
Ex: SET=19°C, RT>19°C and AT>20°C.
Step-2
Heating Entry:
If (SET-RT) = (1 to 3°C), Medium duty cycle Heater ON for 30 sec and OFF for 30sec.
Ex: SET=19°C, RT<18 °C and AT<17°C.
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Step-3
Heating Entry:
If (SET-RT)>3°C, Medium duty cycle Heater ON for 55 sec and OFF for 5 sec.
Ex: SET=19°C, RT<17 °C and AT<16°C.
10.6. De-Humidification
Dehumidification process starts, if the relative humidity of return air is more than 60%.
During 5 min cycle in this process, first compressor and heater are ON, while Second compressor remains in OFF position.
The heater Duty Cycle is 30 sec ON and 30 sec OFF.
After 5 minutes the Relative Humidity is again monitored, and if still it is more than 60%, the cycle repeats till the RH is reached less than 60%.
10.7. Shut Down Mode
Air Conditioning system will be shut down when the Air-Con switch is turned OFF or when there is no 400 V level supply.
Controller selects the corresponding mode at which the operating will be shut down sequentially i.e., if it is in Heating mode / Pre-Heating Mode, Heaters are switched OFF and if it is in Cooling / Pre-Cooling mode, compressors and condensers are switched OFF with the time delays assigned between them.
10.8. Manual mode
The Manual mode can only be activated through serial interface and application software with the help of laptop. This Mode makes testing of the individual outputs of the system.
10.9. Sleep Mode Operation
The controller automatically enters the sleep mode operation during pre-defined night hours which can be changed to suit the requirement for different seasons and places.
At the start of sleep mode operation, controller gradually increases the coach temperature in equal steps to a predefined value within specified time period and maintains the same during the night hours.
At the end of night hours, the processor gradually reduces the coach temperature to selected value within pre-defined time period.
The set temperature during night hour as well as its time period can be altered by the maintenance staff.
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10.10. Other Functions of Controller
The controller will continuously monitor the duty cycle of compressors. If duty cycle of both the compressors is recorded to be less than 40% for four consecutive cycles, only one of the compressors will be worked alternatively. Again if one compressor is not able to achieve the desired temperature within 10 minutes, both the compressors will start working simultaneously.
Once the compressors are switched off, the first compressor starts after a time delay of 2 minutes and the second compressor starts after 30 seconds of starting of first compressor in order to control initial inrush of current.
During winter season when the coach temperature reaches 2°C below the set value, the heaters are switched ON. The heaters will remain ON till the set temperature is achieved.
In the event of any defect, malfunction or abnormality, the unit isolates the equipment of RMPU or shuts down the system, depending upon the nature of defect to prevent any unsafe operating condition for the RMPU.
11. PROTECTION DEVICES (MCBs AND FUSES)
NAME DESCRIPTION SUPPLY VOLTAGE
F-01 MCB (Triple Pole) 10A for Ventilation Fan Motor Unit 1 (Blower Motor-1)
415 VAC
F-02 MCB (Triple Pole) 10A for Ventilation Fan Motor Unit 2 (Blower Motor-2)
415 VAC
F-03 MCB (Triple Pole) 20A for Compressor Motor 1.1 415 VAC
F-04 MCB (Double Pole) 10A for Crankcase Heaters (for CP 1.1 & CP 1.2)
220 VAC
F-06 MCB (Triple Pole) 10A for Condenser Fan Motor 1.1 415 VAC
F-08 MCB (Triple Pole) 6A for Heater Unit-1 (NPPS) 415 VAC
F-10 MCB (Double Pole) 10A for Crankcase Heaters (for CP 2.1 & CP 2.2)
220 VAC
F-14 MCB (Triple Pole) 16A for Heater Unit-2 (PPS) 415 VAC
F-35 MCB (Double Pole) 6A for AC Compact Controller 110 VDC
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F-79 HRC Fuse (63A) in R-phase for Radiator Motor, Roof Extractor-1 & 2
415 VAC
F-80 HRC Fuse (63A) in Y-phase for Radiator Motor, Roof Extractor-1 & 2
415 VAC
F-81 HRC Fuse (63A) in B-phase for Radiator Motor, Roof Extractor-1 & 2
415 VAC
F-82 HRC Fuse (63A) in R-phase for Radiator Motor, Roof Extractor-3 & 4
415 VAC
F-83 HRC Fuse (63A) in Y-phase for Radiator Motor, Roof Extractor-3 & 4
415 VAC
F-84 HRC Fuse (63A) in B-phase for Radiator Motor, Roof Extractor-3 & 4
415 VAC
K-26 Contactor for Ventilation Fan Motor Unit-1(Blower- 1/NPPS)
110 VDC, 415 VAC
K-28 Contactor for Ventilation Fan Motor Unit-2 (Blower- 2/PPS)
110 VDC, 415 VAC
K-31 Contactor for Condenser Fan Motor 1.1 110 VDC, 415 VAC
K-33 Contactor for Compressor Motor 1.1 110 VDC, 415 VAC
K-35 Contactor for Heater Unit 1 (NPPS) 110 VDC, 415 VAC
K-40 Contactor for Heater Unit 2 (PPS) 110 VDC, 415 VAC
U-4 Air Conditioning Control Switch Panel 24 VDC, 110 VDC
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13. THREE PHASE POWER TERMINAL FOR RMPU
Terminal no. Description Terminal no. Description
231
Ventilation-1
256
233 258
247
Heater-1
272
250
253
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14. ADDITIONAL FEATURES OF RMPU DOUBLE DECKER (which are different from LHB EOG AC coaches)
RMPU capacity increased from 7 TR to 10 TR, and the refrigerant used is R 407 C, eco- friendly refrigerant. These AC units are designed as per RDSO spec. no. RDSO/PE/SPEC/AC/0134-2009 (Rev.0) with amendments 1, 2, 3.
• 2 nos. 60 kVA step-down transformers are provided in each coach. These are shifted towards ends of the coach. The 750 volts, 3-phase, 50 Hz input is stepped down to 415 volts 3-phase, 50 Hz and fed to the 415 v supply system of the Double Decker coach.
• As the space for ducting in the centre of the coach was not available, specially designed ducting along the sidewall has been provided for upper and lower deck.
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CHAPTER 2
Schedule D1 : Trip / Weekly
Schedule D2 : Monthly ± 3days
Schedule D3 : Half Yearly ± 15 days
Shop Schedule (SS-1), IOH : 18 Months+30 days/6 Lakh kms whichever is earlier
Shop Schedule (SS-2), POH : 36 Months /12 Lakh kms whichever is earlier
Shop Schedule (SS-3), POH : 72 Months/24 Lakh kms whichever is earlier
As per RDSO’s Maintenance Schedule No. RDSO/PE/SMI/AC/0044-2011 (Rev.0) dated 02/04.11.2011 and ‘Maintenance Manual for LHB Coaches’, following maintenance activities to be carried out on roof mounted AC package unit of LHB design coaches:
2. General
Activities TI
(D1)
M
(D2)
HY
(D3)
IOH
(SS-1)
POH
(SS-2)

--

d. Cleaning of air grills -
e. i) Remove return air filters by opening the access doors of the unit. Clean these filters with compressed air after taking out the filters and place them gently in their places or replace with pre-cleaned/ new filter/ filter media and close the doors properly. A cleaning jig should be available with AMC holders/ Railways for this activity.

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--
---
-- --

k. Check the tripping of heaters i.e. OHP. The OHP setting is 65°C. The testing of OHP setting shall be done by switching off the blower. During testing, the probe of digital thermometer shall be placed near the sensor of OHP & the display shall be kept outside.
-- --
To b
e re
p la
ce d
l. Check whether ESTI cartridge is provided with bulb and properly screwed.
-- --
To b
e re
p la
ce d

Normal currents for various equipments and mode of operation are as under:
Package unit in cooling mode - 20-23 Amps
Compressor - 7.5 – 9.5Amps.
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Condenser fan motor - 1.5 – 2.1 Amps.
Blower motor - 1.5-2.5 Amps
Note: The current also depends on the ambient temperature.
--
d
-- --
-- --
-- --
r. Capillary type HP/LP cut out should be replaced with HP/LP cut-out without capillary during IOH/POH.
-- --- --
--
-- --
d
-- --
d

w. Check anti-vibration mountings of overall package unit. Replace if required.
-- AVM for over all package unit to
be replaced
--
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RDSO’s SMI ELPS/AC/SMI/14.
y. Check insulation resistance of all the motors & compressors by the duly calibrated 1000V megger. Attend the motors, if insulation resistance of motor is found less than 2M ohm.
Important: Disconnect microprocessor controller during this activity.
-- -- --
-- --
z-i Check for the physically damaged conduits. Replace them, if needed.
-- -- To be replaced during POH
z-ii Harting connector to be replaced -- -- --
2.1. Refrigerant Pipe Line/ Capillary
Activities TI (D1)
a. Check for proper clamping/ support. -- -- --
-- -- --
-- -- ---
M (D2)
HY (D3)
IOH (SS-1)
POH (SS-2)
-- --
-- --
-- --
-- --
-- --
-- --
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2.3. Condenser Fans Motor/ Blades and Blower Motor/ Impeller
Activities TI (D1)
-- --
-- --
c. Ensure double earthing shunts are provided. -- -- --- To be replace
d during POH
d. Check condition of blade/impeller for its fixing/ cracking/ breakage/ damage or touching with its cover. Rectify/ replace, if needed.
-- -- To be repla ced durin g POH
e. Ensure proper clamping of cable conduits. -- --
f. Overhauling of Blower and condenser fan motors shall includes the following during POH.
The incoming motors shall be checked for abnormal noise and vibration.
Check bearing make and replace with specified make,
• The IR value of motor stator shall be measured between motor terminal and frame before and after overhauling. The
value of IR shall not be less than 5 M, when measured with 1000 volt megger.
-- -- -- --
-- -- -- --
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Perform HV (Di-electric test) on stator by applying 1.5 kV AC supply for one minute. During test the leakage current shall also be measured, which shall not be more than 1.0 mA.
Run motor on no load for 15 minutes and check the following.
i. Bearing noise – Normal noise.
ii. Bearing temperature rise above ambient
should not be more than 10°C.
iii. SPM reading – 20dBM max.
(Green zone)
Measure starting current of motors on no load. It shall not be more than 10 times of normal running current. Similarly, the running current of motors shall be measured and it shall not be more than 1.4A.
Spray water over running motor by jet having 10mm dia from all side. After spray, check IR value. There should be no drop in IR value.
Ensure the continuity of TOP.
Anti tracking varnish
g. Ensure that impellers are properly tightened. -- -- ---
-- -- ---
Activities TI (D1)
a. Ensure that filters are not damaged.
-- -- --
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2.5. HP/ LP/ OHP Cutout Switch
Activities TI (D1)
-- --
-- --
-- --
-- --
---
-- -- --
g. Remove the accumulated dust over feeler tube of OHP switch.
-- -- OHP to be
b. Ensure proper clamping of electrical wires to heater.
-- --
-- --
M (D2)
HY (D3)
IOH (SS-1)
POH (SS-2)
-- --
c. Remove the dust accumulated over sensor gently.
-- -- To be
repl aced
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2.8. Expansion Valve/ Capillary Tubes
Activities TI (D1)
M (D2)
HY (D3)
IOH (SS-1)
POH (SS-2)
-- ---
-- --
-- ---
-- -- -- -- *
M (D2)
HY (D3)
IOH (SS-1)
POH (SS-2)
-- --
-- -- --
-- --
(i) Cleaning through blower in D2.
(ii) Cleaning through water jet in D3.
--
-- -- --
Activities TI (D1)
M (D2)
HY (D3)
IOH (SS-1)
POH (SS-2)
-- -- --
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NOTE: 1. Never use “Antifreeze liquids” like methyl alcohol together with a filter
drier. Such liquid can damage the filter. 2. Never re-use a filter drier. 3. To avoid chances of moisture ingress in the system, filter drier & compressor should be installed immediately after evacuation and charging the system.
2.11. Access Doors
Activities TI (D1)
M (D2)
HY (D3)
IOH (SS-1)
POH (SS-2)
a. Insulate service doors, lower portion and side wall from inside of the evaporator compartment.
-- -- -- To be
repl aced

-- --
M (D2)
HY (D3)
IOH (SS-1)
POH (SS-2)
-- --
b. Ensure free flow of condensate water. --
-- -- --
NOTE: Epoxy coating of RMPU trough by mechanical staff to be ensured in SS2**
2.13. Condenser Area
Activities TI (D1)
M (D2)
HY (D3)
IOH (SS-1)
POH (SS-2)
--
-- --
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properly tightened.
-- -- -- ---
-- -- --
f. Ensure proper clamping of electrical conduit. -- -- --
-- -- --
-- -- --
Table 1: IR value for different circuit voltage
Sr. No. Circuit Voltage Capacity of Megger used Min. value of IR required
1. 750V 1000V 05 M ohms
2. 415V 500V 03 M ohms
3. 230V 500V 02 M ohms
4. 190V 500V 02 M ohms
5. 110V 500V 02 M ohms
6. 24V 100V 01 M ohms
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CHAPTER 3
1 Compact control MCB F-35 on microprocessor has NO indication
1) 110V DC supply not available
2) Glass fuse on microcontroller has blown
3) Microcontroller faulty/defective
1) Ensure 110V DC supply 2) Replace glass fuse 3) Replace Microcontroller
2 With MCB-F35 ON, AIR-CON switch ON, but NO output of Micro-controller
1) 415V AC supply not available
2) Check NO contact of K23, replace if required
3) NC contact of K27 not working
4) Blower motor T.O.P tripped
1) Ensure 415V AC supply 2) Replace glass fuse F73 or
contactor K23, if defective 3) Check and use spare
contact of K27 4) Check overheating of
motor
3 MCB F-35 ON, AIR- CON switch ON, only BLOWERs are working
1) Controller OK indication not glowing
2) K-27 contactor not working
1) Replace Micro-controller 2) Check DC supply on K-27,
if supply available check NC contact.
4 MCB F-35 ON, AIR- CON switch ON, blower motor starts and trips
1) Vent 1 & 2 indication continuously glowing
1) Check NC contact for blower motor contactor K-26, K-28. If contact OK motor tripped due to phase over heating
5 Condenser motor 1.1 and 2.1 not working
1) Condenser motor 1.1 temperature ok not working
2) Condenser motor 2.1 temperature ok not working
1) TOP of condenser motor tripped check and rectify
2) TOP of condenser motor tripped check and rectify
6 a. Condenser motor 1.2 not working even if HP indication is glowing on Micro- controller
1) Control pressure indication not glowing
2) Temperature condenser motor1.2 not glowing
1) Control pressure switch defective replaced it
2) Motor tripped at TOP, check for over heating
b). Condenser motor 2.2 not working of even if HP
1) Control pressure indication not glowing
1) Control pressure switch defective replace it
2) Motor tripped at TOP,
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indication is glowing on Micro- controller
2) Temperature condenser motor2.2 not glowing
check for over heating
7 Compressor not working
2) LP indication not glowing
3) HP indication
internal overload
1) Set temperature setting Low
2) Check suction pressure and compressor current, recharge gas if required. If LP output are ok check LP switch, replace if defective
3) Check if second motor not working replace it, clean the condenser unit if found dirty.
4) Ambient Temperature is high or solenoid valve not operating check the circuit.
8 Heater not working 1) Temperature selector switch set at Low
2) Temperature heater on indication not glowing
3) ESTI fused
2) OHP tripped or CKT may be checked
3) Replace ESTI
9 DC supply tripping as MICR output signal ON
1) Contactor coil or diode suppressor may be short circuited in condenser or compressor contactor
1) Remove both plant output voltage connectors from Micro- controller and identify the defective contactor by reconnecting one by one and replace the defective contactor
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ANNEXURE-1
FUNDAMENTALS OF AIR-CONDITIONING Air conditioning is the controlling of air temperature, its humidity, its purity, noise-free and its flow rate at a certain place to produce a comfort zone.
Ventilation is refreshing the air in a crowded place by feeding the place with amount of air at a certain time and drawing the same amount of air to obtain a healthy environment empty of dust, gases and bad smell. Human’s Comfort The human needs water, food and air for a healthy life. The healthy requirements are: One third of the feeding air must be fresh air and the 2 third return air after purifying. Entire air in the air conditioned areas must be moved at a velocity between 0.15 to 0.25
M/s. This velocity doesn’t cause a noise. Comfort means treatment of 5 properties of air
1. Dry bulb temperature (d.b.t) : cooling or heating 2. RH (%) : humidification or de-humidification 3. Air purity : Free from dust & bacteria 4. Ventilation : Fresh air to provide the needed oxygen 5. Air movement : homogeneous flow rate and distribution
(Static air causes temperature difference of about 8-16 degree C between the breath level and the ceiling level)
Temperature
BASIC TERMINOLOGIES IN AIR CONDITIONING 1. Kilo-Calorie
It is defined as the amount of heat to be added /removed to raise /lower the temperature of one kg of water by one degree Celsius.
2. BTU
It is defined as the amount of heat to be added (removed) to raise (lower) the temperature of one pound of water by one degree Fahrenheit.
1 Kilo Calorie = 3.97 BTU. 3. Sensible heat
It is that heat which when applied to a body, results in a rise of its temperature without any change in its physical state. It is the heat which is sensed by a thermometer. Eg: - Heating of water
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4. Latent heat
It is that heat which when applied merely changes the state of substance, whether solid, liquid or gas, without causing any change in its temperature. Latent heat can not be sensed by a thermometer but can be measured by Kilo-Cal per Kg or BTU per lb.
Eg: - Melting of ice without change in temperature. Latent heat of fusion of ice 80 k.cal/kg (144 BTUs/lb).
5. Enthalpy
It is calculated property of vapour which is defined as "Total heat content ". It is the sum of the sensible heat and latent heat.
6. Critical Temperature
There is a defined temperature for every liquid or gas, which is called it's critical temperature, beyond which any amount of increase in pressure cannot liquefy it. The temperature when below it's critical point, the gas can be liquefied without lowering it's temperature but by increasing it's pressure.
7. Humidity The amount of water vapour present in the air is called humidity. 8. Specific Humidity
The amount of water vapour present in one kg of air is called specific humidity. 9. Relative Humidity (RH)
It is the ratio of the actual amount of moisture contained to the maximum amount required for saturation and is expressed as a percentage.
RH = Actual amount of water vapour present x 100% Maximum amount required for saturation.
10. Temperature & Pressure Relationship
Water boils at 100 degree C when the pressure on it's surface is atmospheric, i.e. 1.003 kg /sq cm.
If pressure is increased to above atmospheric, i.e. more than 1.003 kg / sq cm, the boiling temperature of water will increase, which happens in pressure cooker.
If the pressure is decreased below atmospheric, i.e. less than 1.003 kg /sq cm, the boiling temperature of water will decrease, which exactly happens when water dried out in an oil centrifuging plant by creating vacuum, at a temperature of about 70 degree C.
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The same thing is also true for other liquid like various refrigerant which evaporates at low temperature when the pressure is suddenly decreased.
11. Expansion Principal
When a gas expands, its temperature falls and when it is compressed its temperature rises.
12. Dry Bulb Temperature (DBT)
It is the temperature of air as measured by an ordinary thermometer.
13. Wet Bulb Temperature (WBT)
It is the temperature of air as measured by an ordinary thermometer, but it's glass bulb is covered by a thin cotton sleeve soaked in water.
When the sleeve is wetted, mercury column of the thermometer will be observed to start dropping down, until it finally settles down at a definite minimum value. Because the water in the wet bulb takes away it's latent heat, as it gets vapourised, from the mercury.
As a result, the bulb gets cooled and the mercury column shows a low temperature. The drop in temperature depends upon the relative humidity of the surrounding air.
When air is heated, the DBT increases, WBT also increases, but at a slower rate and therefore, the difference between DBT and WBT widens indicating a lower humidity.
When air is cooled, it becomes more and more humid, until it becomes fully saturated and the difference between DBT and WBT goes reducing until it becomes zero at saturation. Hence, at saturation the DBT & WBT are equal.
If cooling is continued further some of the moisture contained in air gets thrown out and will condense, since air has a limited holding capacity for moisture.
14. Dew Point Temperature (DPT)
It is the temperature of air at which the moisture of air starts condensing on the surface. Relative Humidity at dew point is 100%.
15. Effective Temperature (ET)
It is an arbitrary index which combines into single factor the effect of temperature, humidity and air movement on human comfort in a noise free environment.
This corresponds to a DB temperature of saturated air at which a given percentage of people feel comfortable. Thus an effective temperature of 21 degree C can be expressed as 23 degree C DB at 70 % RH or 25 degree C DB at 30% RH.
16. Coefficient of Performance (COP)
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Ratio of heat absorbed from refrigerated space and equivalent heat supplied to compressor.
17. Ozone Depletion Potential (ODP)
• Relative value that indicates the potential of a substance to destroy ozone gas as compared with the potential of Chloro-Fluoro Carbon-11 (CFC-11 or R11) which is assigned a reference value of 1.
• Thus, a substance with ODP of 2 is twice as harmful as CFC-11. R-22, for example, has an ODP of 0.05.
18. Global Warming Potential (GWP)
Global Warming Potential (GWP) is a relative measure of how much heat a greenhouse gas traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide.
19. Psychrometry
The measurement of moisture content in air is known as psychrometry. The air is basically a mixture of dry air and water vapour. The relative amount of water vapour in atmosphere is very small. Variations in amount of water vapour as well as change in temperature are very significant and important in air conditioning.
20. Unit of Refrigeration
The unit employed for designating Air Conditioning capacity is “Ton of Refrigeration (TR)”.
The capacity of a plant is said to be one ton, if it is capable to extracting heat at a rate equivalent to that required to freeze one American ton (2000lbs) of water at 0°C into ice at the same temperature in 24 hrs.
OR
One ton of refrigeration is the heat required to melt one American ton (2000lbs) of ice at 0°C into water at the same temperature in 24 hrs.
1 ton of Refrigeration = 2000 lbs X 80K.cal/kg.
= 907.198 kg x 80 K.cal/kg
=72575.84 K.cal/24 Hrs
=3024 K.cal/hr 21. Refrigerant
Refrigerants are the fluids that change their state upon application or removal of heat within a system and, in this act of change, absorbs or release heat to or from an area or
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substance. Many different fluids are used as Refrigerants such as R-12, R-22, R-134a, R- 407c etc.
21.1 Desirable Properties of a Refrigerant
Low boiling point
Low freezing point.
Low specific heat because high specific heat decreases the refrigerating effect per kg.
High latent heat because high latent heat at low temperature increases the refrigerating effect per kg of refrigerant.
Low specific volume to reduce the size of the compressor.
High thermal conductivity to reduce the area of heat transfer in evaporator and condenser.
Non-flammable.
Non-explosive
Non-toxic
Non-corrosive.
High COP in the working temperature range. This is necessary to reduce the running cost of the system.
High miscibility with lubricating oil and it should not have reacting property with lubricating oil in the temperature range of the system.
Should not have any bad effects on the stored material or food, when any leak develops in the system.
The leak should be easy to detect.
High Electrical Resistance to prevent electrical short.
It should not have harmful effect on the environment i.e. Environment friendly. (Global Warming & Ozone layer depletion).
Pressures required to be maintained in the evaporator and condenser should be low enough to reduce the material cost and must be positive to avoid leakage of air into the system.
Must be readily available and must be cheap. 21.2 Name of Refrigerants
• Ammonia (NH) : Ice making, cold storage.
• Sulphur di-oxide(SO) : Domestic refrigerator.
• Methyl chloride (CHCL) : Small Domestic refrigerator.
• Carbon Dioxide(CO) : For manufacturing Dry ice,
• Monoflouro trichloro Methane (F-11)
• Dichloro Diflouro Methane (F-12)
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• Trifluro monochloro Methane (F-13).
• Monoflouro dichloro Methane (F-21).
• Monochloro Difluro Methane (F-22).
• Trifluro chloro Ethane (F-113).
• Tetra fluro Ethane (R-134a) • R407c- Substitute for R22 Refrigerant blend containing R32, R125 and R134a
(23/25/52% by weight).
Chemical name Tetrafluotoe thane
Boiling pt °C -46.1 -26.2 -40.8 -29.8
Freezing pt °C -142 -256 -252
Critical temp °C 86.22 102 96 112
Critical pressure 4.62 MPa
Cylinder colour Orange Light sky blue Green White
21.3 Description of R-407C
• Refrigerant blend containing R32, R125 and R134a (23/25/52% by weight).
• Temperature glide approx 7K
• Refrigerant must be charged from liquid phase Physical and thermodynamic properties comparable to R22.
• Non-flammable and safe to use commercially available miscible with polyol ester oils.
• Chemical Name: Di-fluoro-methane, penta-fluoro-ethane, 1,1,1,2- Tetra-fluoro- ethane
22. VAPOUR COMPRESSION CYCLE
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i) Compressor
ii) Condenser
iii) Expansion valve
iv) Evaporator unit.
22.1 Compressor (Compression) Refrigerant is drawn from evaporator in dry vapour & low pressure state by suction strokes of the compressor. In compression stroke, the refrigerant pressure being increased due to increase pressure of vapour, temperature of vapour increase and send to the condenser unit for condensation. (Refrigerant in high pressure & in vapour form)
22.2 Condenser (condensation)
It is intended for cooling the hot gas & liquefying it. It may be air cooled or water cooled. High temperature refrigerant in vapour state is received in condenser unit where the heat is rejected with the help of natural air of condenser fan, which results refrigerant returns to liquid state. (Refrigerant in high pressure & in liquid form).
22.3 Expansion Valve (Expansion)
Expansion valve is provided just before evaporator unit. After condensation, the liquid refrigerant passes through this valve and enters this evaporator unit at low pressure & low temperature. Its function is to control & regulate the rate of flow of liquid
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refrigerant under high pressure and allow it into the evaporator under low pressure or expended the refrigerant. The expansion valve admits more refrigerant when air conditioning load is high & reduces it to minimum when load is low. (After expansion refrigerant in low pressure & in liquid form).
22.4 Evaporator (Evaporation) Expanded low pressure liquid refrigerant enters into the evaporator unit and converted into vapour form by gaining latent heat through circulating air with the help of blower fan thereby cooling the space and thus refrigeration cycle is completed.
This constitutes the cooling unit, in which the liquid refrigerant under low pressure evaporates and do so, it takes away its quota of latent heat, thereby cooling the medium surrounding the cooling coil. (After evaporation refrigerant in low pressure & in vapour form)
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REFERENCES
2. RDSO specification no. RDSO/PE/SPEC/AC/0139-2009 (Rev.1)-Dec, 2011 for Microprocessor Controller for Roof Mounted AC Package Unit for LHB Coaches and Double Decker Coaches.
3. RDSO specification no. RDSO/PE/SPEC/AC/0134-2009 (Rev.0)- July, 2009 for Roof Mounted AC Package Unit for Double Decker EOG type Air Conditioned Coaches (10TR).
4. RDSO Special Maintenance Instructions no. RDSO/PE/SMI/AC/0044-2011 (Rev.0)- Nov., 2011 for Maintenance Schedule of LHB RMPU.
5. Maintenance manual for AC EOG LHB coaches issued by CAMTECH, Gwalior.
6. Operation and maintenance manual for RMPU and Microprocessor Controller issued by various OEMs.
7. Literature and photographs collected from various field units.
8. Suggestions and feedback received from field units of Indian Railways.
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CAMTECH is continuing its efforts in the documentation and
up-gradation of information on maintenance practices of
electrical assets. Over the years a large number of
publications on electrical assets have been prepared in the
form of handbooks, pockets books, pamphlets & video films
etc. These publications have been uploaded on the internet as
well as rail net.
For downloading these publications please do following: 1. On internet visit :www.rdso.indianrailways.gov.in
Go to Directorates CAMTECH Publications for download Electrical Engineering
2. On Railnet visit RDSO website at 10.100.2.19
Go to Directorates CAMTECH Publications for download Electrical Engineering
For any further information regarding publications please contact:
Dy. Director (Elect.) BSNL: 0751- 2470740 (O) Rly. : 03747203
: 9752447030 (CUG) SSE/Electrical : 9755549297 (CUG)
E-mail : [email protected]
Write at : Dy.Director (Electrical) Indian Railways Centre for Advanced Maintenance technology, In front of Hotel Adityaz, Airport Road, Maharajpur, Gwalior, Pin code – 474 005

booklet on roof mounted package unit of lhb ac coaches

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