What are the major considerations when implementing Variable Refrigerant Flow systems in multifamily properties?

VRF systems distribute refrigerant to multiple indoor units from the same outdoor system to provide both heating and cooling, depending on the needs of the space, time of year, etc. VRF’s potential for high energy efficiency is achieved through its use of variable speed compressors, which allow the compressor to modulate its operating strength/capacity based on the HVAC needs in the spaces the system supports. Compressors that cannot vary their speed operate at either full capacity or are off, whereas variable speed compressors can ramp their compressors up proportionally. 

There are additional differences in the types of VRF systems that have implications on their operational strengths, flexibility, installation complexity, and efficiencies. For example, whether a VRF is a heat-recovery or non-heat-recovery system (also called a heat pump system) will determine if simultaneous heating and cooling can be provided to different indoor units across the system. Heat-recovery VRFs can provide simultaneous heating and cooling, whereas heat pump systems provide either heating or cooling. 

If your building seeks to provide heating in some areas and cooling in others, it is imperative to utilize a heat recovery VRF system that allows for simultaneous heating and cooling. Using a VRF system in a multifamily building can be beneficial, but there are some real challenges and potential drawbacks to be considered when opting for VRF. For more best practices on VRF, consult this resource. 

Potential Pros to VRF: 

• All-Electric – Like other heat pumps, VRF systems provide electric heating and cooling and can eliminate the need for on-site fuel combustion, which is critical for decarbonization. 
• Space Saving – Because multiple indoor units link to one larger outdoor unit, VRF systems may have a smaller footprint than rooftop condenser farms. 
• Simultaneous Heating and Cooling – VRF systems can provide heating in one area and cooling in another, allowing for flexibility when compared with larger central systems that may only allow for heating or cooling during a given time. 
• Energy Efficiency – Because VRFs are essentially big heat pumps, they have the potential to operate very efficiently (if designed, installed, and maintained correctly.)  

Considerations and Potential Drawbacks: 

• Heavy Use of Refrigerants – VRFs use a lot of refrigerants and have long refrigeration lines, which can make leak detection difficult. Because many refrigerants have a global warming potential hundreds of times higher than CO2 (R410A has a GWP of 2,088), a single refrigerant leak can have incredibly adverse effects on the climate. Additionally, a leak can cause comfort issues for residents in multiple units. 
• System Design – As with any HVAC system, sizing a VRF system appropriately is critical to ensure efficient operation and resident comfort. Because they serve multiple spaces at the same time, sizing VRF systems requires coordinating the load requirements of each space served and selecting both indoor and outdoor units that meet the load requirements.  
• Installation and Commissioning – Many HVAC installers and contractors are not familiar with VRF, and the length of refrigeration line and amount of refrigerant that goes into a VRF means that one mistake can cause a lot of problems. It’s critical to work with an installer who has experience with these systems and to utilize commissioning throughout the installation process to minimize the potential for future problems. 
• Maintenance –Many building maintenance workers are not familiar with VRF systems. Proper training, routine maintenance, and ongoing commissioning are critical to ensuring efficient operation and speedy recovery from any issues that may arise during system operation.