INTRODUCTION

PETRA’s Air-Cooled Liquid chillers (APSa) with semi-hermetic screw compressors and R134-a refrigerant, are available in a wide range of sizes to meet customer requirements for different applications.

APSa chillers offer state-of-the-art low sound, reliability, high energy efficiency and a small physical footprint.

PETRA’s APSa chillers are designed to be shipped as a complete factory package which are 100% test run in the factory. Unit capacities range from 44 – 525 nominal tons at 50 Hz and from 50 - 600 nominal tons at 60 Hz.

APSa chillers consist of low-pressure drop coolers and V- shaped condenser coils to maximize airflow.

PETRA’s APSa chillers are equipped with a microprocessor controller with unsurpassed features, capable of managing the unit performance for optimum efficiency at both full load and part load values.
 

OUTSTANDING FEATURES

Superior Efficiency

The APSa series exceeds the new ASHRAE 90.1 efficiency levels at both full and part load efficiency.
 

Low Noise Chillers

The APSa chillers offer low sound power levels, measured in accordance with the BS ISO 3744 standard.
 

Compact Physical Footprint

The APSa chillers feature compact footprints and the possibility for close- spacing installation to serve the areas that have space constraints.
 

Outstanding Finishing

• All copper pipes and headers are Acra Clad after being cleaned, to maintain pipe material and brazing protected against all external conditions.

• All coil U-Bends are protected with a painted galvanized steel cover plate, The plate covers the whole U-Bend coil side.

• Suction lines and other insulated pipes are wrapped in cheese-cloth and epoxy painted. This gives further protection for the insulation
  against weather and other factors.
 

Quality Assurance

To ensure the best performance, all the chillers in the APSa series are:

• Factory test run

• Produced in an ISO 9001-2000 listed manufacturing facility.

• Rated in accordance with ARI standard 550/590.
 

Easy Installation

Installation is made quick and easy with complete factory wiring, easy lifting provisions, factory installed options and start-up. To eliminate potential start-up problems, a complete factory test run is performed on each unit.
 

Design Flexibility

The APSa chillers meet the same high engineering and performance standards that are characteristics of all PETRA air- conditioning systems. A wide range of capacities and options for the APSa series are available to meet precise design requirements.
 

FEATURES AND BENEFITS

Compressor

• Suction gas-cooled semi-hermetic screw compressor

• Universal application

• Rain-tight terminal box

• High-efficiency profile

• Double-walled pressure - compensated rotor housing, which is extremely stable and results in additional sound attenuation

• Proven, long - life bearings with pressure unloading

• Optimized oil management. Built-in directly flanged on

• Oil separator, long life fine filter mesh and magnets on oil circuit, pressure relieved bearing chamber ensures minimum refrigerant dilution
  in the oil

• Large volume motor for part winding or Start-Delta with integrated PTC sensor in each winding

• Intelligent electronics including thermal motor temperature monitoring, phase sequence monitoring, manual reset lock-out and
  discharge temperature protection by PTCs sensors

• Dual capacity control with infinite and slide control

• Automatic start unloading

• Discharge shut off valve and discharge check valve

• Rubber-in-shear isolation

• Oil level switch, high efficiency suction strainer, oil strainer crank case heater and built-in safety pressure relief valve
 

Condenser

• PETRA'S air-cooled condenser coils are designed to deliver their duties with optimum performance for all design conditions. Coils are
  manufactured from seamless copper tubes mechanically expanded into aluminum fins.

• All coils are air pressure tested at 450 Psi, under water to avoid leakage. They also undergo dry cleaning after manufacturing for optimum system
  cleanness.

• Type-L, heavy wall, seamless copper tubes are provided for the coil headers. The condenser coils are hydrostatic pressure tested in accordance
  with the UL 1995 standard.
 

Direct Drive Condenser Propeller Fans

• All condenser fans are of the axial type, sickle-shaped blades, statically and dynamically balanced, selected for optimum efficiency and maximum
  sound power reduction.

• Fan blades are driven by an external rotor motor and protected by a wire guard made from steel, coated with oven-baked electrostatic polyester
  powder coating.
 

Condenser Fan Motor

• All fan motors are of high efficiency external rotor motor with permanently lubricated bearing.

• Six pole induction type motor.

• Motors are with class F insulation provided with inherent motor protection.
 

Coolers

• High efficiency shell and tube type coolers with inner grooved tubes to optimize the cooler’s efficiency. Coolers are tested and stamped for
   refrigerant side working pressure of 225 Psi and for waterside working pressure of 150 Psi.

• These working pressures comply with applicable sections of the ASME standard, and the European codes of ISPESL and TUV.

• Cooler water baffles are fabricated from brass for maximum corrosion resistance.

• Coolers are provided with water vents and drain connection plugs and are insulated using (3/4 inch) closed cell foam insulation as the standard
   insulation thickness.

• Other thicknesses are available as options.
 

STANDARD FEATURES

Construction

• Galvanized C-channel chiller base with lifting lugs painted with acrylic polyurethane paint.

• V-shaped, air-cooled condenser, covered with protective panels, allows less installation space requirements.

• Modular design with multiple compressor execution provides flexibility for varying load conditions and avoids total shut down of the chiller
  during servicing of any of the refrigeration circuits.

• Easily accessible system components

• Weatherproof with ample space for easy access power and control panels

• Heavy duty mounting chassis for the whole unit coated with weatherproof, polyester powder electrostatic paint, oven-baked to ensure
   maximum gloss and hardness.

• Anti-vibration mounts under compressor (rubber pad type).
 

Refrigeration

• Independent refrigeration circuit per compressor

• Liquid, discharge and suction pipes are all hard copper pipes. They are formed using the highly accurate CNC pipe bending machines in order to
  minimize pipe-brazed joints which in turn increases system reliability.

• Components of each refrigeration circuit:

               - Expansion valve
               - Liquid line solenoid valve
               - Liquid line shut off valve
               - Liquid line moisture indicator sight glass
               - Replaceable core type filter
               - Fully charged unit with R134-a refrigerant
               - High safety pressure switches (capsule type; factory pre-set)

• Epoxy paint for all exposed copper piping system of the refrigeration circuit

• Liquid injection kit

• Stepless capacity control for each compressor (25-100%)
 

Electrical

• Inherent motor protection for each compressor Part winding start and Start- Delta.

• Inherent motor protection for each condenser fan motor

• Smart lead-lag operation for compressors

• Compressor electronic current monitor and overload protection through controller.

• Free terminal for remote ON/OFF connection

• Free terminal for general alarm output

• High ambient kit

• Control voltage is 220-240V for all components

• Power supply monitor (phase failure relay)

• Single point power connection for each electrical panel (refer to electrical data tables)

• Circuit breaker for each compressor

• Starting contactors for compressors and condenser fan motors

• Automatic pump down control

• ON/OFF switch for each compressor

• Control circuit breaker for short circuit protection

• Short cycling protection for compressors (time delay)

• Control transformer sized to supply the needs of the control circuit, sourcing power from the main unit power connection.

• Microprocessor controller for full management of chiller operation and safety circuits
 

OPTIONAL FEATURES

Construction

• Chiller Sound Enhancement Options There are 3 options to enhance the chiller sound pressure level:

                  - Compressor compartment with standard fan
                  - Ultra low fan speed 720 rpm/900 rpm (50/60Hz) and compressor with compartment
                  - Specially designed fan blades with external rotor motor and compressor with compartment

• Coils Protection Material There are 3 options for coil material:

                  - Polyurethane pre-coated aluminum fins with copper tubes
                  - Copper fins with copper tubes
                  - Polyurethane post-coated copper fins with copper tubes

• Galvanized steel wire mesh guard around the chiller’s perimeter

• Chiller Vibration Isolation: The following options are available for chiller vibration isolation:

                  - Neoprene rubber pads
                  -1inch Spring isolator
 

Refrigeration

• Cooler tape heater: Factory installed heater to protect cooler from freeze-up at low ambient temperatures down to (-20°F).

• Ice storage option: Special chillers are available for this option; please consult PETRA factory for more details.

• Glycol option: Used for applications requiring water outlet temperature below 40°F.

• Suction valves for compressors larger than 90 HP

• Suction accumulator

• Liquid receiver

• High pressure relief valve

• Pressure gauges (High + Low)

• Electronic expansion valve

• Water flow switch: Required as a safety interlock to prevent operation of the unit without evaporator flow (available for field installation only).

• Cooler cladding can be aluminum, stainless steel or polyester painted, 22 gauge, galvanized steel

• Cooler insulation: Cooler can be insulated with 1.5 inch thick or more closed cell foam insulation.
 

Electrical

• Low ambient head pressure control If the chiller is intended for use in low ambient conditions (below 7°C), low ambient control must
  be added. This can be achieved by varying the speed of the condenser fan motor by using a variable frequency drive. The speed of
  the condenser fan motor can be regulated with reference to the high- pressure sensor to maintain constant condensing pressure in the
  condenser.

• Unit mounted fused or non-fused disconnect service switch with external handle to isolate unit from power for servicing.

• Ground current protection for whole unit power supply. The current is monitored by toroidal coils around the power leads.

• Building automation system connection

• External overload for each compressor

• External overload for condenser fans

• Ampere meter and/or voltmeter installed on the electric panel door

• Circuit breaker for condenser fan motors

• Main power circuit breaker for the whole unit with door isolator