Mitsubishi Electric Hybrid VRF (HVRF) Series: Low-Refrigerant Solutions for Commercial Buildings

The commercial air conditioning industry is facing increasing pressure to reduce refrigerant volumes and adopt systems with lower environmental impact. The Mitsubishi Electric Hybrid VRF (HVRF) Series is designed to meet these requirements. By combining VRF technology with a water-based distribution system, it reduces refrigerant use inside occupied spaces while retaining the flexibility and scalability of traditional VRF.

This blog explores the full HVRF range, installation considerations, compatible indoor units, technical details, and examples of its application across Hampshire, Berkshire, Surrey, and Oxfordshire. A Q&A section addresses common questions from contractors and project managers.

Explore our commercial installation services:
https://www.climateworks.co.uk/commercial-air-conditioning

Why Choose Hybrid VRF

HVRF systems are designed to meet both environmental regulations and end-user expectations. Instead of circulating refrigerant throughout the building, refrigerant is confined to outdoor units and a Hybrid Branch Controller (HBC). From there, water is used to distribute heating and cooling to indoor units.

Key advantages include:

• Reduced refrigerant charge compared to conventional VRF
• Compliance with safety standards for occupied spaces
• Simultaneous heating and cooling with energy recovery
• Easier maintenance due to water-based secondary circuit
• Scalable capacity for medium to large commercial buildings

This makes HVRF particularly suited for:

• Schools and universities
• Hospitals and healthcare facilities
• Hotels and multi-occupancy buildings
• Large offices with sustainability goals

HVRF Outdoor Unit Range

The HVRF Series uses the same outdoor units as Mitsubishi Electric’s City Multi VRF systems, adapted for hybrid operation.

Representative modules include:

• PUHY-P250YNW-A2-HVRF – 25 kW (8 HP)
• PUHY-P400YNW-A2-HVRF – 40 kW (14 HP)
• PUHY-P600YNW-A2-HVRF – 60 kW (22 HP)

Scalability and performance:

• Systems up to 150 HP (over 400 kW)
• Long pipe runs to HBC units
• Modular expansion for phased projects

The Role of Hybrid Branch Controllers (HBC)

The HBC is central to the Hybrid VRF system. It transfers energy between the refrigerant and water circuits, allowing simultaneous heating and cooling using water distribution.

• Two-pipe design simplifies installation compared with conventional three-pipe VRF
• Compact modules allow placement close to indoor units
• Scalable design with multiple HBC units in large systems

Compatible Indoor Units

Hybrid VRF connects to the full City Multi indoor range, but with water replacing refrigerant as the heat transfer medium.

Indoor unit options include:

• 4-way ceiling cassettes – for open spaces such as classrooms and offices
• Compact cassettes – fitting shallow voids
• Slim ducted units – for refurbishments with tight space
• Medium and high static ducted units – for auditoriums and large rooms
• Ceiling-suspended units – straightforward retrofits
• Wall-mounted units – for small offices and meeting rooms
• Floor-standing units – for perimeter comfort
• AHU connections – for integration with mechanical ventilation

Technical Specifications

• Refrigerant: R410A confined to outdoor and HBC units
• Capacity range: 22–150 HP modular
• Pipe length: Standard VRF allowances to HBC; water pipe runs to indoor units
• Vertical rise: Up to 90 m
• Operating range: Cooling –5 °C to 46 °C; Heating –20 °C to 15 °C
• Indoor unit connections: Up to 50+ depending on design

Installation Considerations

HBC Unit Placement

• Install close to clusters of indoor units
• Allow for water pipework routing to individual zones
• Provide adequate access for service

Water Pipework

• Standard water pipe installation practices apply
• No refrigerant inside occupied spaces, improving compliance
• Easy integration with building hydraulic systems

Electrical and Controls

• Each outdoor and HBC unit requires a dedicated circuit
• Control via M-NET ensures smooth integration
• Compatible with Mitsubishi Electric’s full suite of controllers

Controls and Monitoring

HVRF supports the same control options as City Multi VRF:

• Local controllers for end-user zones
• Centralised building control panels
• BMS integration with BACnet, Modbus, or LonWorks
• Cloud-enabled interfaces for remote monitoring and diagnostics

Local Project Examples

Reading University

HVRF systems were installed in teaching spaces to reduce refrigerant in occupied areas. Indoor water distribution ensured compliance with building safety standards.

Basingstoke Healthcare Facility

A clinic adopted HVRF for consultation rooms and wards. Water pipework simplified compliance while still offering heat recovery benefits.

Guildford Hotel

Guestrooms were fitted with HVRF-connected cassettes, improving safety and reducing total refrigerant volume.

Oxfordshire Office Campus

A corporate office development used HVRF to achieve sustainability targets, with water distribution reducing overall environmental impact.

Benefits of the HVRF System

• Reduced refrigerant in occupied areas for compliance and safety
• Two-pipe simultaneous heating and cooling
• Energy savings through heat recovery
• Flexibility in indoor unit choice
• Scalable capacity for medium and large projects
• Improved sustainability profile for new and refurbished buildings

Q&A

Q: What is the difference between HVRF and standard VRF?
HVRF uses water instead of refrigerant inside occupied spaces, reducing refrigerant volume while retaining VRF flexibility.

Q: How does the HBC unit work?
The HBC transfers energy between the refrigerant circuit and the water circuit, enabling heating and cooling using only two pipes.

Q: Is HVRF suitable for hospitals?
Yes. It reduces refrigerant risk in patient areas and complies with safety standards.

Q: Can HVRF integrate with existing water systems?
Yes. It can connect to building water distribution, provided correct commissioning is carried out.

Q: Does HVRF support simultaneous heating and cooling?
Yes. The system allows recovery between zones just like the R2 system.

Installation Tips

• Position HBC units strategically for clusters of indoor units
• Use insulated water pipework to prevent condensation
• Train facility staff on water system maintenance
• Record commissioning values for refrigerant and water circuits
• Coordinate installation with plumbing contractors on larger jobs

Why ClimateWorks Recommends HVRF

For projects in Hampshire, Berkshire, Surrey, and Oxfordshire, HVRF offers a forward-looking solution. By reducing refrigerant use and improving compliance, it supports both sustainability goals and regulatory requirements. It is especially suited for schools, healthcare, and large office buildings.

Learn more:
https://www.climateworks.co.uk/commercial-air-conditioning

References

1. Mitsubishi Electric Hybrid VRF Product Catalogue
2. Mitsubishi Electric HVRF Technical Guide
3. CIBSE Guide B2: Ventilation and Air Conditioning
4. IET Wiring Regulations (BS 7671)

Author Bio
Dr. Julian Carter is a highly experienced thermal systems expert with over 15 years in the field, holding a PhD in thermal systems. His career spans academic research, consulting, and teaching, focusing on air conditioning and refrigeration systems. Dr. Carter bridges the gap between theoretical advancements and practical applications, providing expert insights to organisations like ClimateWorks, where his guidance informs decision-making and industry best practices. Notably, he has worked on international projects with organisations such as Daikin Industries, the International Institute of Refrigeration (IIR), and the United Nations Environment Programme (UNEP). These collaborations addressed energy efficiency, sustainable refrigerants, and advanced cooling technologies. Currently a lecturer at Edinburgh University, Dr. Carter combines his expertise with a passion for educating the next generation of engineers and advancing climate control technologies.

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