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Jobin Varghese of Mitsubishi Electric explains why a hybrid approach can help designers and contractors find the right solution for their air conditioning system choices

If you asked me to sum up in one word the main challenge for engineering designers and contractors when it comes to working on projects today, I’d say: “Balance”.

Legislation and environmental drivers are putting the onus on engineers to find solutions that square occupant comfort and wellbeing with objectives such as reduced carbon emissions, energy efficiency and minimised embodied carbon.

Balancing these requirements will test the skills of any building services professional, particularly if we add to the mix legislation on safety.

Finding a balanced approach for air conditioning systems is the key to success when designing for today’s projects

Jobin Varghese Jobin Varghese Product Manager for VRF and HVRF


Take the F Gas regulations, for example. Aimed at removing environmentally-damaging hydrofluorocarbons from use, the F Gas regulations have created significant change in air conditioning systems.  

The industry has shifted from high GWP (global warming potential) refrigerants such as R22 (now banned) to new low-GWP alternatives.

Mitsubishi Electric introduced R32 (with a GWP of 675) to its VRF range in 2018, and we have seen wide adoption of these systems since then.

Contractors are aware that since R32 is categorised as ‘mildly flammable’, the BS EN 378 standard requires use of leak detection and alarms in enclosed spaces where R32 is present.

So, the specification of an R32-based system must be balanced with these safety requirements.

And it’s a challenge that isn’t going away soon. In 2021, there will be further reduction in HFC quotas, which will push the market further down the R32 route.

Comfort versus efficiency

Another example of often-conflicting requirements is occupant comfort and energy efficiency.

Achieving a comfortable indoor environment across the year must be calculated against the financial and environmental costs of energy use.

Identifying a system which can provide stable and comfortable cooling or heating in an energy-efficient way is another challenging decision for contractors and consultants.

At Mitsubishi Electric, we understand that reconciling the regulatory and client requirements for new-build or refurbishment projects can be a headache.

That was one of the main drivers behind our development of our Hybrid VRF City Multi system. It is an approach that combines the best elements of VRF with the best of chillers to provide a balanced solution.

A unique approach

Hybrid VRF is a 2-pipe heat recovery VRF with water between a Hybrid Branch Controller (HBC) and the indoor units.

This means it can be designed and installed just like a VRF but with the benefits of a chiller system. It’s energy efficient and highly effective at providing ideal indoor environments, with the ability to heat and cool simultaneously if required.

And because the refrigerant is contained only in the outdoor unit, the indoor units carry only water into occupied spaces.

As a result, no leak detection or alarms are required in an occupied space. What’s more, the whole system uses around 30% to 40% less refrigerant than a standard VRF system, making it easier to comply with F Gas regulations (and more cost-effective to maintain in the long-term).

Now available as floor-standing

Hybrid VRF has proved very popular in a diverse range of buildings from hotels and offices to hospitals and schools. And to help meet the design and installation needs of such distinct projects, we have recently added a vertical Hybrid Branch Controller as an alternative option to our horizontal controller.

This floor-standing unit has been developed with a small footprint (800 x 500mm), so it is small enough to fit into a maintenance cupboard or linen room. BS EN 378 rules will apply in the space where the vertical HBC is installed, so leak detection, alarm and continuous ventilation will be required within that room – though not the rest of the building.

The idea behind the vertical, floor-standing HBC is to make installation, commissioning and maintenance even more straightforward.

Taking the branch controller out of the ceiling makes the Hybrid VRF solution suitable for even more projects, including refurbishment of buildings where the ceiling-mounted approach may not be achievable.

Finding a balanced approach for air conditioning systems is the key to success when designing for today’s projects.

We believe that by continuously updating our Hybrid VRF system, Mitsubishi Electric is helping its customers respond to the challenge of developing energy efficient, comfortable and compliant buildings.

Jobin Varghese Product Manager for VRF and HVRF at Mitsubishi Electric