As the name suggest the precision control of temperature & humidity is achieved by precision Airconditioners (PAC’s). Unlike comfort application it is not for air-conditioning of people but it is used for cooling of high heat generating IT & electronic equipment’s, with a capacity of maintaining a tolerance limit of +/- 1°C in temperature and +/- 2% in Relative Humidity. This system works on high sensible heat ratios.
Sensitive electronics must be maintained in a stable environment of 20 – 25°C temperature with a relative humidity of 40% to 55% all- round the year. The computers and electronic equipment generate large quantities of heat in small areas, nearly 6 to 10 times the heat density of normal office space, the air conditioning system must have more than just enough cooling capacity. It must have the precision to react quickly to a drastic change in heat load and prevent wide temperature and humidity fluctuations.
PAC’s are widely used in below application:
Since the appliances like IT servers are operational 24/7 , the PAC systems also has to work for 24/7 round the clock.
COMPONENTS OF PRECISION AIRCONDITIONERS
Indoor Unit
COMPRESSOR: These units are equipped with higher efficient scroll compressor/ Digital scroll compressor or Inverter Scroll compressor on demand. Features low vibration, low noise and high reliability which works 24/7. Unlike Comfort AC compressor in PAC system are fitted inside Indoor unit only.
EVAPORATOR: Finned tube evaporator with high heat dissipation efficiency is used. The distributor, with its model-specific design, ensures that the refrigerant is distributed evenly in each loop, improving the evaporator efficiency to a great extent.
THERMAL EXPANSION VALVE – The external equalizer type thermal expansion valve collects temperature and pressure signals at the same time, so that it can regulate the refrigerant flow more accurately. Electronic expansion value can also be used for enhanced performance.
HUMIDIFIER/DEHUMIDIFIER/ELECTRICAL HEATER – Humidifier or dehumidifier fitted in the unit is adjustable to a wide range of water qualities, with fast start-up and high humidifying efficiency important in order to control the static electricity in the air. Electrical Heaters are used to lower humidity of space.
EC FAN – The system uses centrifugal backward or forward curve EC (electronically controlled) fan with high efficiency and reliability, large airflow and long blowing distance. This are very low noise fans.
AIR FILTERS– High efficiency Air filters are used to remove dust & other particles from supplied air.
FILTER DRIER – The filter drier can effectively eliminate the moisture in system within a period of time, filter the impurities generated during long-term system operation and ensure normal system operation.
MICRO-PROCESSOR CONTROLLER– Each Precision AC is equipped with an advance microprocessor controller
The controller is a microprocessor programmable logic controller. It has Separate indication of operating modes (cooling, heating, humidifying and Dehumidifying), alarm conditions (temperature high, loss of sensor, Compressor HP & LP, wet floor, no air flow and low humidifier water).
ROOM TEMPERATURE AND HUMIDITY SENSOR-Room Temperature and Humidity level to be set in the Microprocessor Controller for the desired condition to be maintain in the Room. Pressure sensors in the floor void to precisely control the supply rate, placing temperature sensors on the intake grills on the server rack is recommended to control the supply temperature from the CRAC units as this matches the actual intake.
Outdoor Unit
CONDENSER COIL- The outdoor condenser unit consists of Fin tube type condenser coil where hot refrigerant transfers heat energy to the atmosphere which was collected from the space to be cooled.
CONDENSER FAN-High efficiency Axial fans are used to blow outside air over condenser coil for effective heat transfer.
TYPES OF PAC
Based on Fluid used
Based on Air discharge
WORKING PRINCIPLE
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