What is the definition of a VRF AC system? VRF stands for Variable Refrigerant Flow, and is a type of air conditioning system that uses a refrigerant, such as Freon, to cool the air. This system is typically used in large buildings, such as hotels, office spaces, and public areas. It works by using a compressor to convert the air into liquid form, and then it is sent through pipes to the various zones of the building, where it is then cooled and circulated. This type of system provides a more efficient way to cool an entire building, and is much more cost-effective than traditional air conditioning systems. It is also much more environmentally friendly, as it does not use as much electricity, and the refrigerant does not deplete the ozone layer. VRF AC systems are becoming increasingly popular in large buildings, as they offer a much more efficient way to cool the air and reduce energy costs.