What is VRF (Variable Rrefrigerant Flow)?

Variable refrigerant flow (VRF) is a commercial air-conditioning system configuration where there is one outdoor condensing unit and multiple indoor units. The term variable refrigerant flow refers to the ability of the system to control the amount of refrigerant flowing to the multiple evaporators (indoor units), enabling the use of many evaporators of differing capacities and configurations connected to a single condensing unit (outdoor unit) and enables zone control. There are different forms of VRF systems, 2 pipe, 3 pipe, air and water cooled along with Gas Driven systems for buildings with power limitations.

Different Types of VRF Systems:

• Heat Pumps system – 2 pipe

VRF heat pump systems commonly known as 2 pipe, permit heating or cooling in all of the indoor units but NOT simultaneous heating and cooling. When the indoor units are in the cooling mode, they act as evaporators; when they are in the heating mode, they act as condensers.

VRF heat pump systems are effectively applied in open plan areas, retail stores, cellular offices and any other area that require cooling or heating during the same operational periods.

• Heat Recovery System- 3 pipe

Variable refrigerant flow systems with heat recovery (VRF-HR) capability can operate simultaneously in heating and/or cooling mode, enabling heat to be used rather than rejected as it would be in traditional heat pump systems. Each indoor unit is branched off from the 3 pipes using solenoid box which contains a series of valves. An indoor unit requiring cooling will open its liquid line and suction line valves and act as an evaporator. An indoor unit requiring heating will open its hot gas and liquid line valves and will act as a condenser. Typically, extra heat exchangers in distribution boxes are used to transfer some reject heat from the superheated refrigerant exiting the zone being cooled to the refrigerant that is going to the zone to be heated. This balancing act has the potential to produce significant energy savings

Three pipe heat pump systems are effectively applied in open plan areas, retail stores, cellular offices and any other area that require cooling and heating at the same time.

• VRF Water Cooled

Most commonly used are air-cooled systems, using packaged outdoor condensing units, which via refrigeration pipework connect to a number of indoor units. There are however some limitations, pipework runs, mainly vertical risers (although Samsung can have a vertical rise up to 115mtere), plant space and noise. Where these become an issue then water cooled systems can be used. They operate as the Air-cooled units, but instead of having a built in air cooled heat exchanger they utilise and plate heat exchanger, which transfers the energy into a water loop.

This is connected to a cooling tower or dry cooler which transfers the energy/ heat to atmosphere. Due to this process the water cooled VRF systems can be placed internally with no worry about the vertical risers, in much smaller areas, taking up less space and can be attenuated to meet most environmental requirements.  These systems are also ideal for building served by an existing landlords condenser water loop.

• Gas Driven

In the event of having a limited electrical power supply, VRF units are available with Gas driven engines, these will operate off a natural gas or Calor Gas supply. They are all single phase units and can produce up 90 Kw of Cooling and heating from one single phase 30 amp supplies. They also offer other benefits such as, hot water generation, electrical generation and they will continue to provide heating evening during defrost periods.