Are VRF (Variable Refrigerant Flow) Systems Right For You? And What Are The Gotcha’s?
The latest wrinkle in commercial air conditioning in the USA is the VRF (variable refrigerant flow) system, widely introduced here within the past decade from Japan and Korea. VRF takes the ductless air distribution model (where the fan coil units typically either hang on the wall within the room, or are mounted in the ceiling and blow directly into the room without ductwork) and extends it to having many indoor fan coil and temperature zones connected to a single outdoor condensing unit. It is obvious that VRF is a popular new technology. It offers the ability to have lots of discreet temperature zones (including tiny zones) and is potentially both quiet and very energy efficient, particularly when compared with many other conventional air cooled AC options. It is often far more expensive to install correctly than most other technologies, despite what the VRF manufacturers and their sales forces may say, so that has to be evaluated to determine if the benefits outweigh the costs for a given application. But as with most things worth knowing, there are aspects of this subject that are not so obvious. There are some potential “gotcha’s” for HVAC system designers.
I discuss two of those “gotcha’s” in my May column in the So Cal ASHRAE Sol Air Newsletter. One is the large amount of refrigerant present in VRF systems, compared with most alternatives. While there is nothing wrong with that in and of itself, it does require analysis during the design phase to make sure that a refrigerant leak at the wrong part of the system would not put too great a concentration of refrigerant into a room. The other is the need for a far more disciplined approach to system start-up and commissioning than most contractors have been practicing…with the consequence that if all the steps are not followed, it is impossible to know how much refrigerant is really needed.
If you would like to know more, this link will take you to the relevant newsletter: http://www.ashrae-socal.org/pdf/SolAir_May%202015_Final.pdf