3. Introduction
What you will know at the end of session?
1. Organizational Set up & a bit of history
2. Basic concepts in Air-conditioning.
3. Capacity and Settings of AC coaches
4. System of Generation
5. Generation in EOG coaches
6. How AC works in AC coach
7. Development of RMPU
8. LHB coaches & Double Decker AC train
9. Take tour of LHB coach
9. Air-Conditioning
The first Indian air-conditioned train was Frontier Mail
which was introduced in 1934. Earlier, the AC coaches of
the train were kept cool by using ice blocks. These were
replenished at several halts along the line. A battery
operated blower constantly blew air into these
receptacles, and the cold air entered the insulated cars
through vents.
British officers used to travel by Frontier Mail. It was a
challenge to maintain the temperature of the AC
coaches.
History of AC coaches
10. Air-Conditioning
The Frontier Mail was
one of the first trains
in India to get an air
conditioned car. The
AC car started
running from 1934.
History of AC coaches
11. Air-Conditioning
The North-Western Railway introduced air-conditioned
stock in the late 1930's (the earliest was probably the
Frontier Mail in 1936 or 1937).
In 1952-53 there were air-conditioned services between
Bombay and Howrah, Delhi and Madras (Grand Trunk
Exp.), Bombay and Delhi, Bombay-Amritsar (Frontier
Mail), Bombay-Viramgam (Saurashtra Mail), and Bombay-
Ahmedabad (Gujarat Mail).
These all used AC units that were mounted beneath the
coach body (underslung), interconnected by pipes.
More on history of AC coaches
12. Air-Conditioning
The first fully air-conditioned train was introduced in
1956 between Howrah and Delhi. Popularly known as
the AC Express, it ran on the Grand Chord.
Later there were two, one running on the Grand Chord
and the other on the Main Line. Another train popularly
known as the AC Express was the Dakshin Exp.
between Madras and New Delhi in the 1960s.
AC Chair Car stock was introduced around 1955. Until
about 1979, air-conditioning was available only in
these and in AC First Class cars.
Around 1979 the first two-tier AC coaches were
introduced.
The first 3-tier AC coaches were introduced in 1993
(RCF)
More on history of AC coaches
15. Air-Conditioning
Air-conditioning – comfort factors
• Factors deciding comfort level
• temperature
• humidity
• draft (velocity of air)
• purity of air
• Noise
• Humidity – ratio of the moisture contained in a
given quantity to the quantity of moisture required
to saturate that quantity at a particular temp. It is
termed as Relative Humidity (RH).
16. Air-Conditioning
Unit of Refrigeration
• Unit of Refrigeration – in ton (TR)
• It refers to the latent heat required to melt a ton of
ice at 32 degree F in 24 hours
• 1 ton = 2000 lbs
• Latent heat of Water to freeze -144 BTU/Lb
1 TR = 2000X144 =12000 BTU/Hr
24
= 3000 k Cal/Hr
18. Air-Conditioning
Relative Humidity
Air has capacity to trap moisture. Its
capacity to trap moisture varies with
temperature.
Temperature 1 Cuf of air
70 deg.F 4 grains
80 deg.F 11 grains
90 deg.F 19 grains
1 kg of water = 15400 grains of moisture
19. Air-Conditioning
Outside ambient air (say 100 deg.
F with 95% RH) is sent over the
evaporator at 40 deg. F, moisture
is condensed. When this air goes
inside the AC compartment it rises
to 70 deg. F and as there is now
less moisture, the RH becomes 50
% inside.
Method to control RH
20. Air-Conditioning
Refrigerant
• Freon 12 or Freon 22 (Chloro-
difluoromethane) gases
• These are chemical Compounds. Freon
is the Trade name. In India the Trade
name is Mafron. Manufactured by
Navin Fluorine Industries
• To be re planned by non CFC gases by
2012 - to reduce Ozone layer depletion
• R-134 (Tetrafluroethane) a is being
used now (Non CFL)
22. Air-Conditioning
Capacity of AC Coaches
As per heat load calculation, Load and
Plant capacity of various Coaches
LOAD CAPACITY
• AC II tier 8 TR 2 Plants x 5.3 TR
• AC Ist 5.3 TR 1 Plant x 6.7 TR
• AC Chair Car/III tier 2 Plants x 6.7 TR
23. Air-Conditioning
Other settings in AC Coach
• Fresh air requirement
– Smoking not permitted 0.35 meter cube/min/
passenger
– Smoking permitted 0.7 meter cube/min/
– passenger
• Air Velocity
– up to 0.2m/sec inside the compartment
– 4 m/sec at the diffuser
24. Air-Conditioning
Temperature settings in AC Coach
Low Medium High
• I AC Cooling 220 C 240 C 260 C
Heating 170 C 190 C 210 C
• II AC Cooling - 240 C 260 C
III AC Heating - 190 C 210 C
26. Air-Conditioning
Air- Conditioned Coaches
• Air-conditioned Coaches broadly classified as-
• Self generating type
• Power for AC equipments is supplied
by axle driven alternators at 110V DC
• End-on generation type
• Power from diesel generated sets (DG
sets) at both ends at 750 V AC 3 phase
50 Hz.
• AC equipments operate at 415 V 3
phase 50 Hz. AC
28. Air-Conditioning
Supply System in End-on-generation
Coaches
• Power supply for air-conditioning, lights and fans is
obtained by tapping from one of the two feeders of
750 V, 3 phase, 50 HZ emanating from the Power
Car
• Each coach is provided with 50KVA transformer
which steps down voltage to 415 V, 3 phase
• All AC equipments i.e. compressor, condenser,
evaporator, heater etc. work on 415V, 3 phase
29. Air-Conditioning
Supply System in EOG Coaches
contd…
• For supply to lights and fans, each coach
is provided with a step down
transformer of capacity 3 KVA - steps
down the voltage from 415 V, 3 phase to
190 V, 3 phase.
•110 V a.c. supply is provided for lamps
and fans by connecting them between
line and neutral of the secondary side of
transformer
30. Air-Conditioning
Supply System in EOG Coaches
contd…
A 24 V emergency battery of 90 Ah
capacity has been provided on the
under frame along with a battery
charger. The battery supplies the
emergency lights provided in the
Coach in the event of a. c. power
failure.
31. Air-Conditioning
Battery Charging at the Terminal
Stations
For pre-cooling , AC Coaches are provided
with
• One 200A capacity battery charger
• The battery charger takes 440 V, 3 phase
supply through special battery charging
sockets mounted diagonally one on each
end wall.
• The battery charger consists of a
transformer and a simple diode bridge
rectifier.
33. Air-Conditioning
Equipments of AC System
Compressor – compresses & delivers gas into
condensers at a high pressure & high temperature
Condenser – it cools the hot gas and liquidates it
under pressure
Expansion Valve – It controls and regulates the rate
of flow of liquid freon under high pressure
Evaporator –the cooling unit in which liquid freon
under low pressure evaporates & in-doing so takes
away the latent heat thereby cooling the medium
surrounding the cooling coil
34. Air-Conditioning
• In conventional type – AC equipments
provided on under-frame
• Operates on 110 V DC supply through 18/25
KW alternators
• Thermostat senses the inside temperature
of the coach
• Battery charger is provided on under-frame
for charging the batteries
• Pre-cooling sockets are provided on either
side of the coach for pre-cooling purpose
AC system in conventional
type Coaches
37. Air-Conditioning
Refrigerant gas leakage from pipes and joints
Heavy weight - coach tare weight increases
Large space occupation by the equipments
Maintenance problems - Huge skilled
manpower required
Consumes more power - Less energy
efficient
Under-slung equipments get hit by ballast,
CRO
Accumulated dust affects heat transfer
Drawbacks of Conventional AC system
38. Air-Conditioning
Development of RMPU
• Reliable static Inverters (for conversion
of 110 volt dc into 3-phase ac)
• Use of 3- phase brushless compact
motors possible.
• Development of Package Units for
Rolling Stock applications
• Disadvantages of Opentype
(underslung) eliminated.
• Weight advantage - one Ton against
three Tons)
39. Air-Conditioning
RMPU of 5.2 introduced in the year
1992 with 25 KW alternator
• AC II tier & AC III tier - Two units of 7.0 TR
• First AC - one unit of 7 TR
• Mounted above the toilets on both ends
supplying conditioned air in the tapered
duct to serve the coach end to end
Roof-Mounted Packaged Unit
(RMPU)
42. Air-Conditioning
Comparison of RMPU with Conventional
under-frame AC system
RMPU Conventional
AC
Weight 900 Kgs
(2 units)
2700 kgs
Installation time 4 hrs 4 days
Refrigerant R – 134a R – 12
Refrigerant
charge
2.85 Kgs 15 Kgs
Danger due to
cattle run over /
flood
Nil Heavy
Down time for
repairs
4 hrs. Very long time
43. Air-Conditioning
Linke Hoffman Bosch (LHB)
coaches
• State of the art coaches
Rajdhani / Shatabdi Exp. Trains
Modern passenger amenities
• Technology transfer
M/s Alstom – LHB of Germany
• Manufactured at RCF, Kapurthala
From the year 2003
45. Air-Conditioning
GENERAL FEATURES OF LHB COACH
IV COUPLER
EXT. SUPPLY
SOCKET
BATTERIES BATTERY FUSE BOX
AC PACKAGE UNIT
FRESH AIR
INTAKE
EXHAUST
FAN
