Variable Refrigerant Flow: the benefits over traditional split systems

By Felix Touza

Senior Consultant

Variable Refrigerant Flow (VRF) heating and cooling systems were developed in the 1980s by a Japanese company, and are also called Variable Refrigerant Volume (VRV) systems by other manufacturers. These systems are categorized as Direct Expansion (DX) systems, where refrigerant is directly piped to an indoor fan coil to either heat or cool the air in the space. The outdoor unit pumps liquid refrigerant to the indoor fan coil via a piping system, with the refrigerant oil mixing with the liquid refrigerant to lubricate the compressor.

The standard constant refrigerant-flow residential split-systems operate on the same principle, but are limited to one fan coil that is connected to a ducted air distribution system. In contrast, VRF systems typically eliminate the need for ductwork and instead utilize multiple small fan coils mounted on a wall or recessed into the ceiling.

VRF systems incorporate single (or dual) compressors to serve a potentially large number of fan coils through a refrigerant piping network. The refrigerant flow in the system constantly varies based on demand and loads, achieved through the use of variable speed compressors. To ensure proper operation and prevent oil loss or excessive pressure drops, these systems employ sophisticated controls to manage the refrigerant flow.

Unlike our standard constant flow split systems, VRF systems offer the ability to cool some rooms while simultaneously heating others. This enhances energy efficiency by utilizing the heat extracted from spaces being cooled and delivering it to spaces in need of heating.

VRF systems offer several advantages over traditional DX split systems:

• Improved room temperature control as each space has its own thermostat.
• Enhanced energy efficiency since the compressor only operates as required to meet heating and cooling demands.
• Simultaneous heating and cooling capabilities.
• Adaptability to larger residential and commercial buildings.
• Ease of adding VRF systems to existing structures, as they typically require only refrigerant tubing and terminal fan-coil units connected to an outdoor unit, without the need for ductwork.

In summary, VRF systems are highly engineered and come with numerous advantages. However, these systems are more sensitive to proper designing, installing and maintenance.