Variable refrigerant flow systems (VRF) are a more sophisticated version of the minisplit HVAC system used throughout the world. They distribute the refrigerant instead of piping hot water and chilled water to each fan coil unit (FCU) or air handling unit (AHU). By supplying different amounts of refrigerant to evaporators, the systems provide simultaneous heating and cooling.
VRF systems vary the amount of refrigerant flowing to a series of evaporation coils in a “common” refrigeration piping system. The evaporation components – HVAC in common terms – can be different sizes and serve many different spaces within a building. Some VRF evaporators can be in the cooling mode and others in the heating mode at the same time.
While VRF systems are relatively new to the U.S., they have been used in Japan and Europe since the 1980s. In Japan, 50 percent of mid-size buildings up to 70,000 square feet and 33 percent of buildings larger than 70,000 square feet use VRF systems.
The initial costs for VRF systems are an additional 5 to 20 percent over those for chilled water systems; however, they are roughly 30 percent more efficient than comparable HVAC systems. Although the equipment cost is higher, the installation cost should be a bit lower because all the evaporators use a two-pipe distribution system.
As you might assume, VRF systems require more advanced controls than a simple thermostat. Nearly all of the new HVAC systems require more advanced controls since they communicate continuously with the components of the HVAC system without human intervention. While these systems may require some programming by the mechanical contractor, they are now nearly “plug and play” from the end-user’s perspective. Modern HVAC systems and controls are installed and maintained by factory-trained service techs much the same as the modern automobile. Gone are the days of the shade tree mechanic. Modern automation controls are the reason the systems are more efficient. They also make it easier to determine if a component of the system needs repair.
The bottom line is VRF systems are one of several modern variable-speed and variable-output systems that provide lower energy costs and quiet, comfortable HVAC operation. There is no need to invest in the old constant-volume, on/off HVAC systems that cost more to heat and cool your buildings. The only decision is how much to invest on the front end to ensure lower energy cost for the long run
