Variable Refrigerant Flow Systems What is VRF?
Many HVAC professionals are familiar with ductless mini split products. A variation of this product, often referred to as a multi split, includes multiple indoor evaporators connected to a single condensing unit. Ductless products are fundamentally different from ducted systems in that heat is transferred to or from the space directly by circulating refrigerant to evaporators located near or within the conditioned space. In contrast, conventional systems transfer heat from the space to the refrigerant by circulating air (in ducted systems) or water (in chillers) throughout the building. VRF systems are larger capacity, more complex versions of the ductless multi split systems, with the additional capability of connecting ducted style fan coil units. They are inherently more sophisticated than multi-splits, with multiple compressors, many evaporators, and complex oil and refrigerant management and control systems. They do not provide ventilation, so a separate ventilation system is necessary. The term variable refrigerant flow refers to the ability of the system to control the amount of refrigerant flowing to each of the evaporators, enabling the use of many evaporators of differing