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Variable Refrigerant Flow (VRF) systems: What are they and how do they work?

8th September 2017

If you're not familiar with air conditioning systems, it's easy to get confused with the different types available, which is why we would like to tell you a bit about Variable Refrigerant Flow systems (or VRF for short) also known as a VRV system variable refrigerant volume and why they may be a good choice for your premises.

VRF -DX systems are used for both cooling and heating as a heat pump option or heat recovery option. The heat pump option would allow the system to operate in heating or cooling. The heat recovery option would operate in heating and cooling modes simultaneously to offer a better temperature control in different areas. This in turn would assist in keeping the running costs down by means of using the refrigerant gasses to transfer the heat to where it is required.


The system’s efficiency is shown as SCOP’s which stands for seasonal coefficient of performance. In layman’s terms, this means for every 1Kw of electricity used, you would get between 5.0Kw to 5.75Kw of heating or cooling from this type of system. This makes the VRF/VRV systems the most cost efficient to run on the market.

The way that this is achieved is by the design of the internal and external heat exchangers to allow a better efficiency in absorbing and discharging the heat as well as the use of the latest inverter technologies used in the design of the compressors and fan motors.

Every system would have one external condensing unit with a number of internal units. The condensing unit would be placed in a suitable location external to the premises. This unit would contain a heat exchanger, compressor, fans and controls. The compressor would compress the saturated refrigerant gas into a super-heated vapour after which it passes through the heat exchanger (external condenser). The condenser fan blows air across the coil to cool the refrigerant into a high pressure liquid. This is then transferred to the internal heat exchanger (evaporator). After passing through an expansion device, the refrigerant expands into a vapour, and in doing so cools down. The indoor fan motor then circulates the warm air within the space across the evaporator, which allows the heat within the space to be absorbed thus cooling the room down. The refrigerant then becomes a saturated suction vapour and is returned back to the compressor.

The mode can be changed from cooling to heating which energises a four-way valve on the heat pump models, which in turn diverts the refrigerant gas in the other direction. The heat is then taken from outside and used to heat the space.

The heat recovery system works in a similar way but with the use of individual indoor unit valves.

Although the external temperature could be as low as -20°C, which to us is very cold, absolute zero is -272°C. This would leave 252°C of available heat which is used to heat the space.

The indoor fan coil units can consist of wall mounted units, floor mounted units, four-way blow cassettes, two-way blow cassettes, one-way blow cassettes, under ceiling units and void mounted ducted units plus a void mounted control box.

Each fan coil unit would be individually controlled by means of a hard-wired remote controller and/or a centralised controller.

Fresh air can also be installed by heat recovery fresh air units and controlled by its own hard wired remote controller, or it could be linked to the air conditioning centralized controller.

This type of VRF/VRV – DX system offers an effective solution when a retro fit is required to existing offices. The installation is made easier due to the type of interconnecting pipe work. The installation time is also reduced which in turn keeps the overall costs down.

We hope that you enjoyed our explanation of Variable Refrigerant Flow systems and found it informative, however that's not all there is to know about these popular systems, which is why we recommend that you get in touch with one of our helpful advisors if you would like to find out more about not only the VRF systems we offer but also our other services too.

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