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Looking at the evolution of VRFs

VRFs001

By Ntsako Khosa

The HVAC industry has seen significant changes and innovations related to VRFs with new terms like VRS and VRV making the rounds. We find out more about the innovations and what this means for the industry.

“VRV was invented in the early 1980s and since then there has been a steady introduction of new brands of VRF products into the market,” says Preggy Chettiar, Business Development manager at HC Heat-Exchangers.

VRF systems have seen significant changes since inception over 30 years ago.VRF systems have seen significant changes since inception over 30 years ago. Image credit: IMD

The VRF technology originally stems from Daikin. Marc Brotherhood, National Product manager at Daikin Air Conditioning explains, “VRV and VRF (variable refrigerant flow), are two different terms for the same technology. Because VRV is a trademark of Daikin Industries Ltd., all other companies that replicate this technology call it VRF. When Daikin launched the VRV air conditioning system in 1982, it introduced the world’s first use of variable refrigerant volume control”. Competition, price and performance are some of the aspects that run any market. Chettiar says this is a good thing because, “with competition comes great innovation and each brand continues to attract a larger market share by driving product efficiencies, hence achieving a competitive advantage”.

VRFs003Technological improvements around the system have led to an enhanced operation. Image credit: IMD

Evolution of VRF

Essentially, VRF is a technology that circulates only the minimum amount of refrigerant needed during a single heating or cooling period matching the buildings or space temperature requirements using minimal electricity. “The technology modulates refrigerant flow by electronically controlling the speed of the compressor. This is achieved through a process known as digital commutation,” says Brotherhood. He also shares that the basics of operation have not changed but materials science as well as mechanical and electrical technology has. “The improvements have led to more superior components over the different evolutions.” He states that some of the changes in their systems have compressors which are fully inverter controlled, liquid refrigerant cooled power electronics as well as VRT (variable refrigerant temperature) control on the indoor units. The automatic refrigerant charge function also automates the charging of the correct amount of refrigerant required in the system.
Chettiar adds that energy efficiency and more recently Seasonal Energy Efficiency Ratio (SEER) have been prioritised by all brands, which is partly due to pressure by regulating bodies in different countries. “Each brand has introduced its own unique competitive advantage while addressing energy efficiency and complying with regulations like EN378.”

As a supplier of most of the brands, these are some of the changes/improvements he’s seen with the system:

  • Total pipe length increases, including the height difference between indoor and outdoor units.
  • Reduced installation space for outdoor units.
  • Continuous heating during defrost mode.
  • Incorporation of heat recovery technologies.
  • Simultaneous heating and cooling.
  • Variable refrigerant temperature technology.
  • Improved oil management systems.
  • Auto dust removal from the Condensing units.
  • High Corrosion Resistant outdoor units.
  • Diverse control options, including the incorporation of 3rd party controls.
  • Hybrid VRF using H2O in lieu of refrigerant in occupied spaces.
  • New R32 refrigerant with reduced GWP.
  • All VRF brands have included Air Handling Unit (AHU)solutions within their product offering allowing the clients to have custom designed AHUs by using the VRF electronic expansion valve kits (EEV) with their matching control modules to achieve the required capacities. This has allowed local manufacturers like HC Heat Exchangers to take advantage of the latest VRF technologies within their AHUs and hybrid rooftop packaged units. “This is one of the new technologies that the engineers like,” says Thomas Aphane, sales engineer at Johnson Controls.
  • Dedicated Outdoor Air Systems – (DOAS) Rooftop units with VRF are also available.

Choosing VRF

The performance and efficiencies of these types of systems are some of the reasons why such systems are popular, VRF systems are installed in varied applications like office spaces, lobbies, auditoriums, hospitals, banks, retail, technical facilities, etc. Brotherhood unpacks this, “typically, many buildings today rely on several separate systems for heating or cooling for year-round comfort, ventilation for high quality environments, and efficient production of hot water. As a result, energy is wasted. To provide a much more efficient alternative, VRF technology has been developed into a total solution managing up to 70% of a building’s energy consumption giving large potential to cost saving with advanced controls for maximum operating efficiency”. He adds, “all indoor units have VRT which modulates the saturated evaporating temperature according to the load and certain indoor units have motion sensors that detect human occupancy which will automatically shut down the unit when no occupants are detected in a room. This unique mechanism achieves more sustainability in the long run, as end users save on energy costs while reducing their system’s carbon emissions. The outdoor units have a very good power factor which results in less reactive power being drawn from power transformers. This, importantly, does not mean that a system will use less power, but rather it reduces the strain on the supply transformer”.

VRFs002A hybrid double door VRF unit. Image credit: HC Heat-Exchangers

Chettiar argues, “the popularity of this technology can be attributed to advanced controls philosophy coupled with great training provided to consultants and contractors by the different VRV/F brands. The majority of the brands have excellent training facilities and have become key stakeholders in industry training and overall upliftment of skills”. Daikin is one such brand as it believes that this raises the level of competence in the industry and ensures the end user can be confident that installers have been professionally trained. “Further to this and for more peace of mind, Daikin technicians work closely with installers by doing pre-commissioning checks during the installation and prior to Daikin commissioning of the systems. Installation of VRF systems can be implemented floor by floor, so that sections of the building can be put into use very quickly thereby enabling the air conditioning system to be commissioned and operated in stages, rather than on final completion of the project,” Brotherhood says.

Looking at the quality of the systems, Chettiar adds that VRF condensing units are designed and manufactured in world class production facilities. “The product designs are continuously improved by large Research and Development teams with excellent testing facilities and laboratories. Furthermore, energy efficiency is a core design feature of VRF equipment, and this is evident in the compressor and heat exchange technologies used in these products.”

In terms of performance, the start-up power requirements are extremely low due to the inverter compressors. “The majority of air conditioning applications have varying building load profiles and varying occupancy, this, coupled with varying ambient conditions is ideal for VRF equipment which provides excellent energy efficiency at part load conditions,” he says. Aphane adds that the system is easy to install, maintain and replace “because one thing that consumes a lot of energy is the running of the compressor so if you slow the compressor when reaching the required temperature then definitely it’ll reduce consumption.”

VRF systems come with different offerings. “There are two options that clients can choose from, heat recovery and heat pump,” says Brotherhood.

Heat Recovery offers simultaneous heating AND cooling from one system. “Free” heating and hot water production by transferring heat from areas requiring cooling (heat recovery) resulting in maximum individual comfort in all areas. “Running costs of VRF heat recovery systems can be 30 to 40% lower compared to water fan coil systems,” he says.

Heat Pump VRF systems can be used for either heating OR cooling operations from one system. These systems have no individual indoor unit controls. “Further to this, one must choose between an Air-Cooled or Water-Cooled outdoor system,” he says. An air-cooled outdoor system is fast and easy to install with no need for additional components like pumps, cooling towers, etc. It also has a low maintenance cost. Operation ranges from 25 – 52°C. Condensers can be installed both outdoors and indoors.

A water-cooled system is installed indoors offering protection from the outdoor elements resulting in high longevity, especially corrosion protection in coastal areas or in high chemical environments. It is mainly suitable for high-rise and large buildings because of the nearly unlimited possibilities of water piping. “This system is not affected by outdoor temperature/climate conditions. It also has lower refrigerant levels thanks to the limited distance between outdoor and indoor units,” Brotherhood adds.

Chettiar talks of a hybrid rooftop unit, a solution that he sees fit for a variety of commercial and light industrial applications. “Such a unit comes about when VRF units are coupled with AHUs. This solution offers the clients applications of specific, cooling, heating, humidification and dehumidification units as well as heat recovery wheels and with various filtration options to suit site requirements.

‘VRV and VRF (variable refrigerant flow), are two different terms for the same technology’ ‘VRV and VRF (variable refrigerant flow), are two different terms for the same technology’ – Marc Brotherhood, Daikin.

VRF and the Kigali Amendment

Industry has shown determination in offering sustainable products that serve the environment well, through various engagements around the world that look at phasing out harmful refrigerants. Chettiar says that this is because the majority of the brands are in Europe and understand the need of having such a solution. “Refrigerants like R32 and R466A which have a low global warming potential (GWP) are being introduced by the different brands. New hybrid units with R32 as the primary circuit and H2O as a secondary circuit have also been introduced.”

“Our development of a VRV with a lower GWP refrigerant will offer significantly enhanced environmental performance compared to the conventional models currently available in the market. Whilst today R410A remains the best solution for VRV systems, the latest technological advances are now set to make the development of an optimised and specifically designed VRV system with low GWP and enhanced refrigerant containment possible. Daikin will be launching smaller system capacities operating on R32 in the near future” Brotherhood shares.

Overall, VRFs have adapted with the changes in the industry, Aphane is confident that changes regarding the phasing down of HFCs presents opportunities for design.

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