Air Conditioning in LHB Variants of AC Coaches PDF

___________________________________________________________________________ 8. SALIENT FEATURES OF AIRCONDITIONING IN LHB VARIANTS OF AC COACHES 8.0 LHB coaches are coaches of special design being mow manufactured by RCF Kapurthala on the basis of design and technological transf...

___________________________________________________________________________ 8. SALIENT FEATURES OF AIRCONDITIONING IN LHB VARIANTS OF AC COACHES 8.0 LHB coaches are coaches of special design being mow manufactured by RCF Kapurthala on the basis of design and technological transfer from M/S ALSTHOM LHB. The air-conditioning of these coaches incorporate micro-processor controlled air- conditioning system with a number of advanced technical features for comfort air- conditioning. The important features of air-conditioning are as follows.The various RMPUS used in LHB coaches are 1) Sidwal make, 2) Fedder lloyd make 3) Amit engineering make 4) Lloyd Electric makes. The AC system is described below based on Sidwal make RMPU ac coach package unit and their systems 8.1 ROOF MOUNTED AC PACKAGE UNIT (SIDWAL MAKE) The AC system for all type of coaches and generator cars of Indian railways provides the following functions in all rooms used by either the train staff of passengers, such as the passenger compartment, staff compartment, WC, kitchen and rooms accommodating the switchgear. Ventilation Air heater Air cooling Air dehumidification Air filtering 8.1.1 CONSTRUCTION The coaches are provided with two Nos compact air-conditioning units each and the generator cars with one air- conditioning unit each. However the units used in the different car type are identical. ________________________________________________________________________ ___________________________________________________________________________ ________________________________________________________________________  ___________________________________________________________________________ Diagram of Control panel in LHB coaches 8.1.2 The AC system for the Passenger and Generator cars 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 Fresh air screen Open/closed-loop control devices Sensors 8.1.3 COMPACT AIR CONDITIONING UNIT ________________________________________________________________________ ___________________________________________________________________________ The compact air conditioner unit has been designed for the air conditioning of 2 tier, 3 tier & chair car for Indian Railways. 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 computer of the air conditioning system. The dimensions of the air conditioning units have been designed to match the car profile. Being installed in a recessed trough, it does not protrude from the car profile. The compact air conditioning unit has two separate cooling circuits consisting of the following components: two hermetic refrigeration compressors with oil heaters two condenser with Cu pipes and Al. Fins two axial fans for cooling the condensers two evaporators two twin-sucking radial fans for the supply air (driven by the motor) three maintenance covers two air inlets for circulating air one air outlet for supply air control and safety devices pipelines/fittings two mixed air filters 8.1.4 Operating modes 8.1.4.1 Preheating and cooling operation The outside air dampers are closed to facilitate rapid heating up or cooling down of the carriage 8.1.4.2 Normal operation In the normal operating mode, the dampers are set to ensure the envisaged fresh air volume of 21 m3/h per person. 8.1.4.3 Emergency operation Should the AC system fail due to a failure of the power supply, the adjusting dampers of the circulating air duct close so that the system is operated exclusively with outside air. ________________________________________________________________________  ___________________________________________________________________________ The supply air fan of the compact air conditioning unit sucks the air from the mixing chamber across the two mixed air filters and evaporators and forces it via the electric heater into the supply air duct of the carriage. The condenser fans concurrently suck fresh via ventilation slots provided on both sides to cool the compressor-condenser section. The supply air is first carried via silencers into the thermally insulated supply air duct, which is diagonally split in the longitudinal direction. The air is then supplied via openings in he bottom into a compensating chamber and from there via the perforated ceiling into the passenger compartment. 8.5 Controller All controlling and regulating functions are performed by the digital controller. It is built in an EMC proof standard plug-in rack using so-called 19” technology that is designed for plug-in cards of Eurocard form factor. This rack contains all required electronic cards needed for the unit. This combination of cards and wiring between the cards have been specifically designed that have been used for many years in high quantities in various railway HVAC equipment. All signals are passed into this device via 2 front-side multiple cable connectors on position X1 and X2, Where as 110V supply is located on a separate front side connector on card A1of controller. 8.5.1Software / operating modes The control of air-conditioning system is divided into the following operating modes: - Test mode - Emergency mode - Control mode 8.5.2 Test mode This mode only supports a test run that uses the dedicated service program PRUEFWIN (in case of Sidwal) and a PC. The PC is connected to a/c computer via the serial port. There is one, command “H”, for “test mode”. The software will switch off all outputs and enter testing mode for duration of 2 hours. During this time any output may be manually. Set or reset with the help of ‘Z’ command, To escape prematurely from testing mode the HVCV controller must be reset by powering off and on the 110V supply. Then the user can test the individual operating functions of the system. 8.5.3 Emergency mode ________________________________________________________________________  ___________________________________________________________________________ If a measuring sensor fails, the system continues in emergency mode. This mode consists of two steps : Step 1 : Evaluation is taken over by the sensor of Out door temperature sensor Defective the other system. Step 2 : Fixed value of 20 degrees C Duct air temperature sensor Defective Control together with room temperature. Step 1 : Evaluation is taken over by the sensor of the other system. Room air temperature sensor Defective Step 2 : Control according to duct temp And outdoor temperature. Set point generator defective Controlled to fixed value of 23 deg. C Room and duct sensors Defective Turns off heating and cooling Ventilation is s possible. 8.5.4 Control mode In controlled service, the air-conditioning units are controlled by a microcomputer. This is a fully automatic operating mode. Depending on the ambient temperature, the available modes of heating, ventilating, cooling and dehumidifying are controlled. 8.5.5 Temperature regulation in pre-heating and pre-cooling Pre-heating uses maximum heater output until an indoor temperature of at least 14ºC, the system changes to “heating in controlled service” mode. To save energy, only recirculating air is used in pre-heating mode. In this mode the fresh air/recirculating air flap is set to extreme position, i.e. „100% recirculating air”. The output must be active at least for ninety seconds to ensure that the flap goes to full open position. Besides the exhaust air fan must not be running in pre-heating mode of the system. Like in pre-heating, pre-cooling also uses maximum cooling output. Pre cooling starts when temperature is greater than 28ºC when the controller cuts in, the required voltage is fed. When the room temperature of 28ºC is reached latest, however, after 30 minutes, the system changes to „cooling in controlled service’ mode. To save energy, only recirculating air is used in pre-cooling mode. In this mode the fresh air/recirculating air flap is set to extreme position, i.e. “100% recirculating air” and the exhaust air fans are turned off. 8.5.6 Temperature regulation in heating, ventilation and cooling modes. ________________________________________________________________________ ___________________________________________________________________________ The room temperature is exclusively controlled by the microcomputer. 8.5.7 Room set point temperature in cooling mode / Heating Mode Switch S1U1R1. Set point generator has 7 point temp. selector switch Summer Winter 20.0°C 17.0°C 1. 20.5 °C 17.7°C 2. 21.3 °C 18.3°C 3. 22.3 °C 19.0°C 4. 23.2°C 19.7°C 5. 24.0 °C 20.0°C 6. 25.0 °C 21.0°C 7. 8.5.8 Cooling circuit control If a cooling power request is received, a safety check is made before the compressor is turned on. The following information is available and should be observed: Thermal monitoring of the condenser fan Suction pressure message High pressure message 8.6 Dehumidification The dehumidification function is available at cooling mode step 2. It is used if the relative humidity of the room air rises to 60%. This condition is monitoring by the moisture sensor in input C7S3. If the relative humidity is less than 60%, a simulated temperature of below 60°C is measured (Appro. 10 kΩ ). When the sensor switches, this resistance is reduced via a measuring bridge so as to enable measurement over (appr.1 kΩ ).During dehumidification, the room temperature is controlled by the extra heater. Extra heating is maintained until The cooling power of the second step becomes insufficient to maintain the room temperature even at maximum cooling output, or ________________________________________________________________________ ___________________________________________________________________________ The moisture sensor relative humidity of less than 60%. In dehumidification service, a max 50% of the cooling output is allowed to ensure that the combined power consumption of the refrigerating and heating units does not exceed the maximum cooling output. This is ensured by limiting the dehumidification function to cooling step 2. The higher power consumption that would be needed if 2 compressors were turned on simultaneously is avoided by delaying the start of the second compressor by 5 seconds. ________________________________________________________________________