Mitsubishi Heavy VRF

VRF systems

A VRF (Variable Refrigerant Flow) air conditioning system is a highly efficient system for cooling or heating air in a medium or large commercial building.

VRF 2-pipe heat pump system

A VRF (Variable Refrigerant Flow) air conditioning system comprises 1 outdoor unit connected to numerous (up to 48) indoor units.

In cooling mode the compressor makes refrigerant in the outdoor unit coil hot (which absorbs 'free' cooling from the outdoor air) and the expansion valves make the refrigerant in each indoor unit coil cold (which cools the indoor air).

In heating mode the refrigerant flow is reversed to produce hot refrigerant coils in the indoor units (which heat the indoor air). In a 2-pipe system all the indoor units are simultaneously either in cooling mode or in heating mode.

VRF 3-pipe heat recovery system

As in a 2-pipe system a VRF 3 pipe heat recovery system comprises 1 outdoor unit connected to numerous indoor units.

By an efficient refrigerant distribution controller, indoor units may take either hot or cold refrigerant from the system according to the requirements of the individual indoor room or zone. A room on the hot side of a building may take cold refrigerant to cool the air at the same time as a room on the cold side of the building takes hot refrigerant to heat the air.

By using refrigerant to recover heat from hot rooms to heat the air in cool rooms a heat recovery system can be even more energy efficient than a standard 2-pipe heat pump system.

Refrigerant

At the heart of an air conditioning system is refrigerant – a chemical substance which gets hotter as it is compressed from gas to liquid state, and gets colder as it is allowed to expand from liquid to gas state.

Early refrigerants were CFCs (ChloroFluoroCarbons, such as R12) and HCFCs (Hydro ChloroFluoroCarbons, such as R22) which caused damage to earth's ozone layer if they escaped (eg from pipe leaks or during poor servicing). Mitsubishi Heavy Industries has been a leader in developing air conditioning systems which use R410a, a modern 'synthetic' refrigerant which has zero ozone depletion potential.

Energy efficiency: CoP and EER

In cooling or in heating mode a VRF system is highly energy efficient; typically 1kW of electricity used by the compressor generates the equivalent of 3 or 4 or more kW of heating energy or cooling energy. The efficiency of the system depends on the design of many individual components, especially the compressor.

Efficiency in cooling is measured by EER (Energy Efficiency Ration): EER of 4 means the system gives 4kW of cooling energy using only 1kW of electrical power.

Efficiency in heating is measured by CoP (Coefficient of Performance): CoP of 4 means the system gives 4kW of heating energy using only 1kW of electrical power.