APSG VFD Screw

Air Cooled Water Chiller with Variable Speed Screw Compressor

As a leading engineering institution in air conditioning high quality products, Petra is proud to introduce its revolutionary design for its new line of Variable Speed Drive Chillers to meet not only the current but also future requirements of efficiency, reliability and sustainability

Petra chilled water equipment established their place in the market, as a highly efficient ultra-low sound AHRI / Eurovent certified system. And now with global concern regarding energy and premium efficient products, Petra is introducing its new variable speed drive chiller series with screw compressors, specially designed to reduce energy consumption at part load with superior efficiency

APSG VFD Screw chillers are the ultimate solution for commercial and industrial applications with high efficiency part load performance and Ozone friendly refrigerants

Petra`s VFD controlled compressor series is AHRI / Eurovent certified and in accordance to the latest ASHRAE 90.1 standards in terms of efficiency and part load performance. Petra`s superior efficiency at part load can reach up to an IPLV value of 5.85 (kW/kW) in the high efficiency versions

As a leading engineering institution in air conditioning high quality products, Petra is proud to introduce its revolutionary design for its new line of VFD Screw chillers to meet not only the current but also the future requirements of efficiency reliability and sustainability.

Petra chilled water systems has stabilized its distinguished place in engineering industries, as a high efficient ultra-low sound AHRI certified equipment. And now with all global concern about energy and questions about the premium efficiency products, Petra decided to proceed its leading industrial role by obtaining the new variable speed screw chiller, specially designed to reduce your energy consumption and to make your comfort level higher.

APSa VFD Screw chiller is the ultimate solution for commercial and industrial applications with the requirements of Confidence, sustainability, and first of all the highest efficiency part load performance.

• VFD on one compressor or VFD on each compressor option
• Wide range of capacities as the compressor works with variable speed to meet the customer requirements for a variety of applications
• Silent operation for sound sensitive projects, as this series has been specially designed with sound sensitive environments in mind. Sound power levels at full load operating conditions are low
• Compact APSG design to keep installation space at the minimum so it’s deal for both new and retrofit projects. In particular the highly efficient compressor with its integrated inverter allows us to mount more compact heat exchangers in the frame and combined with the interfaced compact control panel, deliver more power from reduced footprint
• Simple to install even simpler to maintain, as APSG chillers are wired at the factory and are also precommissioned with the unit’s software tuned and set points already established. They also integrate easily with exciting building management systems. So on site all that is required is to plug the unit into the power supply, connect any pipes and wires, and switch the unit on
• High energy efficiency performance on Integrated Part Load Values (IPLV)
• Variable speed screw air cooled chillers increase the IPLV value to 20-25% better performance and power
• Soft start provided as standard to reduce power in-rush at start-up
• Rotor profile designed for maximum efficiency at higher speeds
• Compact, high-efficiency, integrated low refrigerant charge evaporator design
• Variable – primary flow chilled water system that varying the water flow reduces the energy consumed by pumps while having limited effect on the chiller energy consumption
• The rotary screw compressor is semi-hermetic, direct drive with capacity control via a variable speed drive, rolling element bearing, and differential refrigerant pressure oil flow and oil heater
• Inverter screw compressor run most efficiently at partial loads, using only the power necessary to match the load required traditional inverter driven unit’s delver high part load efficiencies but can suffer when running at full load
• This series has been specially engineered with sound sensitive environments in mind. Sound power levels for screw chillers with variable speed compressors have much less levels than the chillers with fixed speed compressors

• Welded structural C-channel base painted with mono component catalyzed primer sprayed paint
• Base is equipped with welded brackets for heavy duty lifting lugs
• Structural members are made from gauge 15 [1.8 mm (0.07 inch)] tubular cross members that are semi welded with stainless steel fasteners. All members & panels (side & roof) are painted with oven baked polyester electrostatic powder paint
• Suction gas-cooled semi-hermetic twin screw compressor with variable frequency drives integrated with advanced control system allow the chillers to match actual load conditions, delivering exceptional part load performance
• Condenser coils are highly efficient microchannel type (MCHE) designed to deliver their duties with optimum performance for all design conditions which reduce refrigerant charge, and the unit weight
• All coils are air pressure tested by dry air up to 2,900 kPa (420 Psi) under water. They also undergo dry cleaning after manufacturing for optimum system cleanness
• Condenser coils are covered with protective panels, to ensure uniform air distribution across the coil face area & provide additional protection for coil from weather elements
• Condenser fans of the external rotor type with many attractive features such as space saving, compact design, optimum cooling, full speed controllability and low starting currents
• High efficiency direct expansion (DX) shell and tube type coolers with inner grooved tubes to optimize the cooler’s efficiency
• Coolers are tested and stamped for refrigerant side design pressure of 1,000 kPa (145 Psi) and for a maximum water side working pressure of 1,500 kPa (220 Psi)
• Independent refrigeration circuit per compressor
• Liquid, discharge and suction pipes are all hard copper pipes. They are formed using automated CNC pipe bending machines in order to minimize pipe-brazed joints which in turn increases system reliability
• Epoxy paint for all exposed copper piping system of the refrigeration circuit
• Components of each refrigeration circuit include liquid line solenoid valve, liquid line shut off valve, liquid line moisture indicator sight glass, high safety pressure switch and replaceable core type filter
• Unit is fully charged unit with R-1234ze refrigerant
• Electronic expansion valve: Electronically Operated Step Motor flow control valves, intended for the precise control of liquid refrigerant flow. Synchronized signals to the motor provide discrete angular movement, which translates into precise linear positioning of the valve piston. Easily interfaced with microprocessor based controllers
• Compressor electronic current monitor and overload protection through controller
• Free terminal for remote ON/OFF connection
• Free terminal for general alarm output
• Control voltage is 220-240V for all components
• Single point power connection for each electrical panel
• Circuit breaker for each compressor
• Starting contactors for compressors and condenser fan motors
• ON/OFF switch for each compressor
• Control circuit breaker for short circuit protection
• Short cycling protection for compressors (time delay)
• Control transformer mounted & wired that shall supply all unit control voltage from main unit power supply to internal components such as (not limited to) solenoid valves, compressor motor protector, compressor crank case heater and microprocessor controller
• Microprocessor controller for full management of chiller operation and safety circuits
• Power supply monitor (phase failure relay) used to protect the power circuit against over or under voltage conditions and against phase loss or loss reversing conditions
• Nema 3X with IP54 minimum enclosure standard electrical panel. Two separate panels, one for power & the other for control
• Separate electrical box for condenser fan motors located on condenser side

• Copper tubes aluminum fins & copper tubes copper fins coil
• Coil corrosion protection including polyurethane pre-coating (for aluminum fins) and polyurethane post-coating (for aluminum & copper fins)
• Sound reduction options including low rpm condenser fan, compressor jacket & compressor compartment
• coil guard placed on the lower part of the unit all over the perimeter to provide protection for unit components, fabricated from gauge 18 [1.25 mm (0.05 inch)] galvanized steel sheet metal & painted with Petra electrostatic powder paint, fitted in place by spring load quick turn latch and is supported upon opening by stainless steel hinges
• Hot gas bypass consists of a mechanical valve capacity regulator used to adapt compressor capacity to actual evaporator load, installed in a bypass line between the high and low pressure sides of the refrigeration system and is designed for hot gas injection into the evaporator just after the expansion valve
• Pressure gauges for monitoring of refrigeration discharge and suction pressure
• Pressure relief valve set to open at a predetermined set pressure to protect pressure vessels and other equipment from being subjected to pressures that exceed their design limits
• Water flow switch installed to prevent operation of unit without evaporator water flow
• Cooler cladding of aluminum, stainless steel or painted galvanized steel {made from gauge 22 [0.7 mm (0.03 inch)}
• Cooler can be insulated with closed cell foam insulation of 25 mm (1 inch), 38 mm (1.5 inch) & 50 mm (2 inch) The insulation density is 48 kg/m3 (3 lb/ft3) with a K-factor of 0.035 W/(m.°K) [0.0203 BTUH/(ft.°F)
• Main disconnect switch used to de-energize the power supply to the chiller during servicing or repairing works because of the door interlock with an external handle that is installed on the electric panel door
• Power factor correction used to improve the power factor level which improves system reliability, minimizes voltage drops and gives better power quality
• Earth leakage relay used in electrical installations with high earth impedance to prevent shock
• Control transformer to supply power input to auxiliary components at 120 or 220 volts, such as (not limited to) bulk head light and GFI outlet
• IP 54 protection, class I electric safety bulk head light
• Ampere-meter & volt-meter used to measure the power current & voltage consumption Ampere-meter is used for each phase
• 120 volt power supply connected through the transformer to provide a 120 volt single phase circuit that is used to operate the electric appliances at site such as laptops, tablets and cell phones
• Speed regulator for condenser fan motors used to permit the unit to operate in low ambient temperature
• Dual power connection, one power entry for compressors & the second for the rest of the unit
• External over load for each compressor
• External over load for each condenser fan motor
• Circuit breaker for each condenser fan motor
• Nema 4x electrical panels made from galvanized steel
• Nema 4x electrical panels made from stainless steel
• Cooler tape heater protection down to 0°C (32°F), -18°C (0°F) & -29°C (-20°F)