Mitsubishi Electric City Multi WR2 VRF Series: Water-Source Heat Recovery for Commercial Projects

Not every commercial site is best served by air-source systems. Buildings with access to water loops, geothermal wells, or district heating and cooling networks often benefit from water-source VRF. The Mitsubishi Electric City Multi WR2 Series is a two-pipe water-source heat recovery VRF, offering simultaneous heating and cooling with the efficiency and flexibility of water-loop energy transfer.

This article explores the WR2 product range, technical capabilities, compatible indoor units, installation considerations, and case studies across the South of England. It also answers common questions from engineers and contractors who specify and install these systems.

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

Why Choose the WR2 Series

The WR2 system is designed for sites where water loops or geothermal systems provide the primary energy transfer medium. By using water instead of air as the heat exchange source, WR2 systems offer several advantages:

• Reduced outdoor footprint compared to air-cooled systems
• Stable performance in extreme climates where air-source systems may struggle
• Ability to connect multiple buildings through a shared water loop
• Simultaneous heating and cooling with energy recovery
• Reduced refrigerant pipe lengths compared with external plant

These benefits make WR2 systems particularly attractive for:

• Large office campuses
• Hotels and resorts
• District energy networks
• Healthcare and research facilities
• Universities and mixed-use estates

WR2 Outdoor Unit Range

The WR2 outdoor modules are water-source equivalents of the air-cooled R2 units.

Representative models include:

• PQHY-P250YHM-A – 25 kW (8 HP)
• PQHY-P300YHM-A – 30 kW (10 HP)
• PQHY-P400YHM-A – 40 kW (14 HP)
• PQHY-P500YHM-A – 50 kW (18 HP)
• PQHY-P600YHM-A – 60 kW (22 HP)

Scalability:

• Systems can be configured up to 150 HP (over 400 kW).
• Indoor/outdoor diversity ratios up to 150%.
• Flexible design allows WR2 units to be sited in plant rooms rather than exposed rooftops.

Compatible Indoor Units

The WR2 system connects with the same extensive range of Mitsubishi Electric indoor units as the R2 system.

• 4-way ceiling cassettes – for open-plan comfort
• Compact cassettes – fitting into shallow ceiling spaces
• Slim ducted units – where void depth is minimal
• Medium and high static ducted units – ideal for long runs in larger spaces
• Wall-mounted units – for simple, discreet zoning
• Floor-standing concealed units – perimeter and partition applications
• Ceiling-suspended units – for open ceilings and refurbishments
• AHU interface units – for integration with ventilation and fresh air systems

This flexibility ensures the WR2 can adapt to varied architectural and operational requirements.

Technical Specifications

Key performance features:

• Refrigerant: R410A
• Capacity range: 22–150 HP modular
• Pipe length: Up to 1,000 m total
• Vertical rise: Up to 90 m
• Operating range (water loop): Typically 10 °C to 45 °C inlet water temperature
• Indoor units: More than 50 per system depending on capacity

The WR2 system takes advantage of water-loop stability to deliver consistent heating and cooling across all seasons.

Installation Considerations

Plant Room Placement

• WR2 units can be located inside plant rooms, freeing up rooftop space
• Ensure adequate ventilation for compressors and components
• Provide clearances for service and maintenance

Water Loop Integration

• Connect to existing condenser water loops, geothermal wells, or cooling towers
• Maintain loop water quality and treatment to prevent corrosion
• Install bypass valves and pumps as recommended by the manufacturer

Refrigerant Piping

• Use approved BC controllers to manage the two-pipe recovery system
• Follow pipe sizing charts and install oil traps where required
• Keep lengths within manufacturer recommendations for system reliability

Electrical

• Dedicated electrical circuits required for each module
• Earthing and breaker sizing to BS 7671 standards
• Control wiring via M-NET for system-wide coordination

Controls and Monitoring

The WR2 system supports Mitsubishi Electric’s full range of control solutions:

• Local wired controllers for room-level adjustments
• Centralised controllers for scheduling across multiple zones
• BMS integration with BACnet, Modbus, or LonWorks
• Energy monitoring interfaces for compliance and reporting
• Cloud-based connectivity for remote diagnostics and optimisation

This control flexibility ensures facility managers can integrate WR2 into existing building systems with minimal disruption.

Local Project Examples

Oxfordshire Research Facility

A laboratory complex installed WR2 units connected to a geothermal loop. The stable water-source environment ensured reliable year-round operation with low running costs.

Basingstoke Business Park

WR2 modules were sited in a shared plant room, connected to a district cooling loop. Slim ducted and cassette indoor units provided comfort across multiple tenant floors.

Reading Hotel

A city-centre hotel used WR2 units to provide heating and cooling across guest rooms, restaurants, and spa facilities. Heat recovery reduced energy bills by redistributing energy between areas.

Guildford University Building

A teaching block connected WR2 to an existing condenser water loop, reducing rooftop plant requirements and freeing external space for solar arrays.

Benefits of the WR2 Series

• Water-source heat recovery for improved stability and efficiency
• Indoor plant room installation frees rooftop space
• Two-pipe design reduces installation complexity
• Scalable capacity up to 150 HP
• Flexible indoor unit compatibility for all project types
• Integration with water loops, geothermal systems, and district networks

Q&A

Q: What is the main advantage of WR2 over R2?
WR2 uses water as its heat source and sink, enabling stable performance in extreme climates and freeing up external space.

Q: Can WR2 connect to a geothermal system?
Yes. WR2 can integrate with geothermal boreholes, reducing reliance on air-source heat exchange.

Q: Does WR2 still provide simultaneous heating and cooling?
Yes. Like the R2, it recovers heat between zones using BC controllers.

Q: Can WR2 be installed indoors?
Yes. Units are typically sited in plant rooms, unlike air-source systems that need rooftop or outdoor space.

Q: Is WR2 compatible with standard indoor units?
Yes. All Mitsubishi Electric City Multi indoor units can connect to WR2.

Q: How do water loop conditions affect performance?
The performance of WR2 depends on stable water inlet temperatures, typically between 10 °C and 45 °C.

Installation Tips

• Check water loop capacity and quality before specifying WR2
• Ensure correct chemical treatment to prevent scaling and corrosion
• Provide adequate ventilation in plant rooms
• Install and commission BC controllers for reliable operation
• Coordinate installation with other trades working in plant spaces
• Train facilities teams on water loop management as part of handover

Why ClimateWorks Recommends WR2

For projects in Hampshire, Berkshire, Surrey, and Oxfordshire, WR2 provides a strong alternative to air-source systems. It is ideal for sites with water loop infrastructure, geothermal potential, or district networks. Its two-pipe design, scalability, and wide indoor unit compatibility make it a versatile solution for commercial buildings that demand efficiency, reliability, and integration with modern energy strategies.

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

References

1. Mitsubishi Electric City Multi WR2 Product Catalogue
2. Mitsubishi Electric WR2 Technical Manual
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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