Evaluating VFD control technology on WVY water-cooled Hitachi air chiller

The cost of electricity consumed during the actual operation of a water-cooled chiller unit can be 8 to 10 times higher than the initial equipment investment cost. Therefore, choosing a solution with superior real-world efficiency is key to balancing the long-term budget. To address this economic challenge, Hitachi has introduced the Hitachi air chiller WVY (Variable Speed ​​Water-cooled Screw Chiller) water-cooled chiller system to the market. The WVY Series not only ensures powerful cooling but also sets a new standard for energy efficiency in modern buildings.

Overview of Hitachi air chiller WVY water-cooled

The RCUF-WVY product line is a water-cooled chiller system using the environmentally friendly R134a refrigerant, designed for durability and meeting stringent environmental protection requirements. The Hitachi WVY chiller system is designed and packaged as a complete, integrated unit directly at the factory. The complete unit structure includes all core components: screw compressor, evaporator, condenser, VFD inverter control panel, touchscreen central control system, and all internal piping and wiring connections. Before shipment, the entire system is pre-coated with protective paint, and pre-filled with oil and R134a refrigerant, minimizing installation time and risks at the site.

To easily identify the technical specifications, Hitachi air conditioners use the following standard model code naming convention:

Example: Model RCUF260WVY

• RCU (Cooling Only Unit): Standard water-cooled chiller unit (cooling only).
• F: Uses R134a refrigerant gas.
• 260 (Cooling Capacity Ton): Nominal cooling capacity in tons.
• W (Water-cooled Unit): Water-cooled design.
• V (Variable Speed ​​Chiller): Integrated variable speed control technology.
• Y (Export Unit): Standard version for the export market.

Detailed evaluation of VFD inverter technology in Hitachi air chiller WVY

Superior Energy Efficiency at All Load Levels

The most notable highlight of this product line is its incredibly impressive energy efficiency. At full load, the unit's COP/EER reaches 5.9. Although in real-world applications, 99% of the operating time is at low load or partial load, the integrated IPLV (Integrated Low Load Efficiency) is the most accurate measure of energy savings. The VFD technology in the WVY series helps achieve an astonishing IPLV of 9.93, far exceeding leading GB energy efficiency standards and the prestigious ASHRAE standard.

Thanks to this optimization, the overall system efficiency increases annually by 20% to 30% compared to using traditional fixed-speed chillers. This results in significant electricity savings for businesses, shortening the payback period to less than two years in most operating scenarios.

Intelligent Power Control Mechanism

The perfect combination of VFD inverter technology and a sliding valve mechanical mechanism allows the Hitachi air chiller WVY to implement stepless control. The inverter plays a key role in flexibly adjusting the frequency in the range of 20Hz to 50Hz. The system provides an extremely wide and deep power adjustment range: from 20% - 100% for single-compressor configurations, and extended from 15% - 100% for dual-compressor configurations. This flexibility ensures that the cooling capacity always closely matches the actual needs of the building at different times of the day, eliminating energy waste when running at low load.

Soft start does not cause voltage drop

A major drawback of traditional chillers is the often high starting current, causing voltage drops in the power grid and forcing investors to purchase large, expensive switching equipment as well as high-capacity backup generator systems. The WVY VFD (Variable Frequency Drive) unit completely solves this problem with its ideal soft-start feature. The starting current is strictly controlled, increasing gradually and never exceeding the compressor's rated current, ensuring the safety of the entire building's electrical system.

Power factor stability

Thanks to its advanced inverter drive system, the Hitachi WVY chiller system maintains an extremely high power factor of 0.95%. This is a significant difference from conventional inverter screw compressors on the market (which experience a severe decline in power factor with load changes). The WVY series' power factor remains consistently stable under all operating conditions, regardless of whether the cooling load increases or decreases. This helps businesses avoid penalties for reactive power from the electricity company.

The WVY series features performance-enhancing technologies

Flooded Evaporator Design

The system's evaporator utilizes a multi-tube flooded design with new technology heat transfer tubes, creating high turbulence in the refrigerant flow and optimizing heat exchange space. The proprietary asymmetrical refrigerant inlet and outlet design fully exploits the physical properties of R134a gas to enhance heat exchange efficiency. Furthermore, the scientifically designed suction baffle completely prevents unvaporized liquid gas particles from being carried back to the compressor, protecting the compressor from hydraulic shock.

Advanced Differential Pressure Oil Separation and Return System

The WVY Series incorporates a high-performance external oil separator, utilizing centrifugal separation technology to thoroughly separate lubricating oil from the refrigerant before it enters the heat exchanger, keeping copper tube surfaces clean and maximizing heat transfer efficiency. In particular, the oil return system operates on the principle of differential pressure combined with intelligent Venturi tube technology to continuously return oil from the oil well to the compressor. Completely eliminating the mechanical oil pump reduces the number of moving parts, minimizes the risk of mechanical failure, and simplifies maintenance.

Integrated Superheater Condenser

The condenser is a removable tube bundle type for easy cleaning, using seamless copper tubes with external fins directly rolled onto the screen. Inside the condenser is a patented superheater structure, providing optimal superheating efficiency for the dielectric cycle, significantly increasing the useful cooling capacity of the Hitachi Chiller system.

Advanced control system and comprehensive protection features

Intuitive, modern, and user-friendly interface

The central control panel uses a dedicated intelligent microprocessor combined with a 7-inch color LCD touchscreen. Operators no longer have to press individual buttons to find information on the old-fashioned, narrow monochrome screen; instead, they can check all operating parameters through intuitive graphical icons. With just a touch, the entire real-time status such as: water inlet/outlet temperature, current, operating frequency, suction/low pressure, gas temperature, and fault warning history will be displayed clearly and immediately.

Superior and Precise Temperature Control

The Hitachi air chiller WVY allows for flexible control options based on inlet or outlet water temperature, depending on the application. The accuracy of outlet water temperature control is extremely ideal (-0.5 to +0.5°C). This rigorous control capability makes the WVY series perfectly suited not only for comfort air conditioning needs (buildings, offices, hotels) but also for precise industrial cooling applications such as sophisticated manufacturing plants or data centers.

Flexible Network Scalability

Through Hitachi's proprietary H-Link communication protocol, the control management system can connect, monitor, and automatically distribute loads across up to 8 chiller units operating in parallel without requiring additional complex external control systems. This multi-unit control system also automatically balances the running hours of each compressor to ensure uniform lifespan for all units.

Strict built-in safety features

System operational safety is protected by multiple layers of high-standard hardware:

• Automatic circuit breaker via overcurrent relay protects the compressor when the current exceeds the safe limit.
• Integrated temperature sensors deep within the motor windings will immediately stop the machine if the temperature exceeds the permissible level.
• Early detection of water flow drop or loss through the tank, promptly ordering a shutdown to prevent freezing and rupture of the evaporator tank.
• Reverse phase protection, overvoltage/undervoltage protection, and a photoelectric oil level switch automatically triggers an alarm to stop the machine if the lubrication oil shortage lasts for more than 1 minute.

The perfect combination of the heart – the new generation G-type screw compressor – and the intelligent VFD inverter control system has made the Hitachi WVY series water-cooled chiller one of the most efficient HVAC solutions available today. The superior energy efficiency at real-world load levels, with an IPLV of up to 9.93, smooth soft-start mechanism, and stable power factor of 0.95, are clear evidence of the groundbreaking technology that Hitachi brings.

From a long-term economic perspective, the WVY series is a smart and secure investment for the future. U.P Tech partners with customers – investors in office buildings, hotels, large hospitals, industrial plants, and modern data centers – to minimize monthly electricity costs, optimize operating expenses (OPEX), and achieve sustainable development goals, creating internationally standardized green buildings.

U.P. TECHNOLOGY AND TRADING CO., LTD.

Hotline: 1800 6202

Email: vu@uptech.com.vn

Website:  https://uptech.com.vn

Transaction Office: 370 Cach Mang Thang 8 Street, Nhieu Loc Ward, Ho Chi Minh City

Head Office: A13, Thuan Viet Commercial Area, 319 Ly Thuong Kiet Street, Phu Tho Ward, Ho Chi Minh City.