INTRODUCTION
Many types of electronic equipment such as computers are highly sensitive to their environment. To function efficiently, they require specific surrounding air temperatures, humidity and filtration conditions. Failure to meet these conditions may result in distorted or lost information. Petra realizes the importance of special environmental control of such highly environment-sensitive equipment and offers the Computer Room Split Air Conditioner "PASC" units which are specifically designed to use wherever temperature, humidity and filtered air have to be controlled continuously within close tolerance limits.
They can be installed in system control centers, telecommunications centers, laboratories, computer server data rooms and others
The new modular design increases sensible heat ratio, by enlarging evaporator area which increases sensible cooling efficiency and reduces running cost.
The wide range of optional features allows the unit to be personalized according to the specific requirements of the environment and the client.
This new modular design provides a wide range of module selection to achieve the required capacity by selecting more than one module for any unit (up to 3 modules for each unit).
More than one module means: Better air distribution by decentralized installation.
The whole unit will not shutdown in case of routine maintenance. Flexibility for units’ extension. Stand-by unit option can be easily installed.
SPECIFICATIONS
Indoor Unit
Casing
Cabinet is constructed of heavy gauge galvanized steel with oven-baked, electrostatic polyester powder paint and internally lined with 25mm thick fiberglass insulation with 48 kg/m density.
The cabinet has decorative front access doors and side panels which can be color coordinated with the decor of the computer room.
Evaporator Coil
The evaporator coil is designed to deliver its respective duty with optimum performance at all design conditions. Coils are manufactured from seamless copper tubes mechanically expanded into aluminum fins. All coils are tested at 3110Kpa air pressure under water to avoid leakage. They also undergo dry chemical cleaning after manufacturing for optimum system cleanliness.
Evaporator Fan
Each module has Double Width Double Inlet (DWDI) forward curved centrifugal belt driven type fan. Fans are statically and dynamically balanced to ensure quiet operation and optimal performance. The fan section features the following:
Permanently lubricated ball bearings Fan deck for improved airflow Draw through airflow for even air
Distribution
Grooved type V-Belts Adjustable blower speed by means of variable pitch motor pulley
Evaporator Fan Motors
Motors are of the totally enclosed induction type, with fan/motor assembly placed on a floating base with flexible connection at the fan/casing interface. The base itself is mounted on rubber-in-sheer vibration isolators to eliminate noise and vibration transition to the building.
All motors have the following features:
- Induction type, single speed, four poles
- High efficiency
- Squirrel-cage
- Internal thermal current protection
- Ip55 protection with class "F" insulation
Filters
Each module has a 50mm thick washable aluminum flat filter.
Drain Pan
Coils are equipped with a corrosion free stainless steel drain pan that is insulated on the sides and underside to prevent condensation.
Condenser Coil
The condenser coil is designed to deliver its respective duties with optimum performance in all design conditions. Coils are manufactured from seamless copper tubes mechanically expanded into aluminum fins. All coils are tested at 3110Kpa air pressure under water to avoid leakage. They also undergo dry chemical cleaning after manufacturing for optimum system cleanliness.
Direct Drive Fan
Fans are of the propeller (Axial) type, which are directly mounted on the motor shaft. Fan blades are made of coated steel for maximum corrosion resistance, and are statically and dynamically balanced before installation. PETRA also provides its "Patented Design" for the condenser fan mounting; this new design offers low noise operation with highly efficient performance. All condenser fans are equipped with wire guards.
Outdoor unit (Air Cooled Remote Condenser)
Casing
Heavy gauge galvanized steel casing coated with oven-baked, electro-static polyester powder paint designed for optimum weatherproof protection.
STANDARD FEATURES
Construction Features
Easily accessible system components Ample space for easy access to power and control panels Rubber anti-vibration mounting for compressor and evaporator fan/motor frame Bottom discharge construction through raised floor. Insulated cabinet constructed from heavy gauge galvanized steel with front access for easy servicing via well insulated doors with hinges.
All units are shipped from the factory tested with safety and control devices set against client requirements.
Easy access 50mm thick aluminum flat filter.
Stainless steel drain pan fitted under the cooling coil.
Refrigeration Features
A filter drier is a very effective method for removing small amounts of moisture and contamination.
Thermostatic expansion device
This device controls the superheat of refrigerant vapor at the outlet of the evaporator.
Filter drier
A filter drier is a very effective method for removing small amounts of moisture and contamination.
Suction accumulator
Its purpose is to protected the compressor from damage due to the sudden return of liquid through suction lines.
Moisture sight glass indicator
It provides a warning signal in the event that moisture has entered the system, indicating that the filter should be changed or that some action needs to be taken to effectively dry the system.
Service charging nipple
Liquid line shut off valve
Pressure switches
The switches are provided to protect the compressor and the refrigeration system from unsafe high and low pressure conditions.
Solenoid valve
Protection device for the compressor.
Electrical Features
Advanced microprocessor controller for full management of unit operation and safety devices with (4*20) user friendly LCD display.
Voltage monitor controller (Phase failure relay) for monitoring the main incoming power supply to the unit, to provide protection for single phasing, under voltage, over voltage, phase-voltage imbalance and phase-nonsequence.
Compressor motor starting contactor. Condenser fan motor starting contactor. Control circuit breaker to protect the control circuit from short circuiting.
Control terminal strip for easy connection to the electrical board and easy field installation.
Humidity control electronic card. Contactor for electrical re-heat coil. Control transformer to supply microprocessor.
Steam humidifier starting contactor. Flood detector for water under floor protection.
Indication lamps for compressor, condenser fan motor, & evaporator fan motor. Internal thermal motor protector for each motor to protect from working under abnormal winding temperature.
Air flow switch: this device is used to provide protection in case of airflow failure
When the supply fan has failed or when the supply air meets any resistance in such a way that reduces heat exchange with the electrical heaters, the controller will prevent the electrical heaters from continued operation and will turn the whole unit off.
Differential pressure switch: This device is incorporated in the unit to provide protection in case of a dirty filter.
Low ambient control: To permit the unit to operate in low ambient temperatures, head pressure control can be installed by varying the speed of the condenser fan motor using a speed regulator or variable frequency drive. Steam humidifier: The steam humidifier is of the immersed electrode type and is based on the most advanced microprocessor technology. It is complete with cleanable cylinder, fill and drain valves, stainless steel distributor and electronic control.
Infrared humidifiers: The infrared humidifier consists of quartz infrared lamps over a stainless steel humidifier pan ready to be connected with water.
Finned tube electrical heating elements with automatic thermal safety cutout and contactors. Maintain the room’s dry bulb temperature during the system dehumidification process.
OPTIONAL FEATURES
Construction Options
Specially treated condenser coil: Available where the air cooled condenser is subject to contaminating or corrosive air stream. Special coatings can be applied to reduce corrosion.
Copper fin /copper tube coils.
Condensate pump: Provided for field installations.
Top discharge construction with supply and return grills.
Centrifugal type condenser fans:
Recommended for indoor installations; allows for ducted intake and discharge.
Semi hermetic compressors
Two compressors for a single module
Water or glycol cooled condenser
Double skin for evaporator side
Synthetic media flat filter
Chilled water cooling coil
Refrigeration Options
Pressure gauges for refrigeration circuit (high/low pressure gauges)
Ozone-friendly refrigerant R-134a for models (PASC 85 - PASC 175)
Hot gas bypass
Extra refrigerant accessories such as liquid receiver, oil separator, etc.
Electrical Options
Power circuit breaker for each motor.
Main power circuit breaker for the whole unit.
External overload for each motor.
Disconnect service switch: a unit mounted non-fused disconnect service switch with an external handle to isolate unit from power voltage for servicing.
Earth leakage relay for each compressor.
Earth leakage relay for the whole unit.
Automatic or manual provision for pump down operation.
Building automation system interface.
Interfacing with other building management systems can be achieved by some additions which can communicate with other devices using the serial communication port.
Graphical display for temperature and humidity with time.
Stand-by function and auto sequencing between units to equal operating hours.
Smoke detector, to provide protection for the system from the hazards of fire that may occur for any reason. The device has the ability to sense the existence of smoke, and if present, it will give a signal to the controller which will shut down the unit.
Main Function of Supervisory System
Modification of control parameters of each single connected instrument.
Local or remote supervisory system.
Reading for temperature and humidity sensors are incorporated in the unit.
Status of the unit (ON/OFF, alarm, stand by).
Alarm management of the unit includes:
a. Display message with detailed alarm description.
b. Print out in real time of detected alarm.
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