Which statement best describes a VRF system?

• A. A Traditional Chilled-Water Central Plant
• B. A System That Uses Only Fixed Flow Refrigerant
• C. An Engineered Direct-Expansion (DX) Multisplit System Incorporating At Least One Variable Capacity Compressor Distributing Refrigerant Through A Piping Network To Multiple Indoor Fan-Coil Units, Each Capable Of Individual Zone Temperature Control, Through Integral Zone Temperature Control Devices And Common Communications Network
• D. A Single-Zone Constant-Capacity System

Answer: (C)

VRF systems are Direct-Expansion multisplit configurations that use a refrigerant piping network to connect one or more outdoor units to multiple indoor units. The standout feature is the ability to vary capacity continuously rather than delivering a fixed amount of cooling or heating. This is achieved with at least one variable-capacity compressor (often inverter-driven) that modulates refrigerant flow to precisely meet each zone’s load. Each indoor unit can be controlled independently by its own zone controls, and a common communications network coordinates operation across the entire system. This combination enables precise, simultaneous zone control and high efficiency.

The other descriptions describe systems that don’t match VRF. A traditional chilled-water central plant uses water as the secondary medium rather than refrigerant and does not provide the same level of zoning with individual indoor-unit control. A single-zone constant-capacity system lacks the multi-zone, variable-capacity capability that defines VRF.