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​Variable Refrigerant Flow (VRF) systems are typically all-electric systems that use heat pumps to provide space heating and cooling to building spaces. They are capable of serving multiple zones in a building, each with different heating and cooling requirements. These systems have the ability to modulate the amount of refrigerant sent to each zone in accordance with conditioning requirements. In contrast, conventional HVAC systems deliver air or water and operate on a full-on or full-off schedule.
Compared with air-to-air heat pumps, VRF offers energy savings due to better part-load efficiencies, heat recovery, smaller zones, and reduced duct losses. Annual energy savings depend on climate zone. Using Energy Pro building modeling software, annual heating and cooling energy savings for a 25,000 square foot assisted-living building are estimated at 37 percent in Seattle, 36 percent in Portland, and 29 percent in Billings.
Current Stage: Approved for Implementation. See BPA Energy Efficiency Implementation Manual and the AIR Northwest site for measure and program details.
​ET Projects

​Variable Refrigerant Flow Heat Recovery (VRF-HR) system lab testing (TI Project #216)

This project develops detailed performance maps of the two primary types of VRF-HR systems: two-pipe and three-pipe. This project will construct a laboratory test facility to test four-zone variable speed VRF Heat Recovery systems over a range of conditions, with a focus on heating performance at lower ambient temperature conditions, where frosting and de-frosting traditionally occurs. Each indoor unit with a thermostat is defined as a zone that allows individual control over temperature and humidity. This performance data will be compared to manufacturers’ data and incorporated into one or more building energy simulation modeling tools. With these energy simulation modeling tools, the energy use of VRF-HR systems can be compared with the energy use of traditional HVAC systems, such as resistance heat, roof top units with gas heat and air conditioning, air to air heat pumps, variable air volume systems, ground source heat pumps. The comparison will allow evaluation of the cost-effectiveness of VRF-HR systems
Project Team
Southern California Edison
2010 – 2012
  • Project Brief
  • TI Summit PowerPoints: 1 2
  • VC HP PowerPoint
  • ASHRAE Paper: Multi-Zone Test Facility for Variable Capacity Multi-Split Heat Pump Systems;
    Upadhye, Harshal; Domitrovic, Ron (2012); 2012 ASHRAE Transactions 2012 Summer Conference San Antonio.

​Multifamily Case Study: Geo-Exchange vs. Variable Refrigerant Flow Space and Water Heating

The Puyallup Tribal Housing Authority set out to build 20 low income housing units with high efficiency of energy use, a project called The Place of Hidden Waters. The multifamily units were built in two separate phases with two nearly identical buildings. Phase 1 uses a Geo-Exchange or Ground Source Heat Pump (GSHP) system in a central heating plant to provide space and domestic water heating for the apartments. Phase 2 uses a central Variable Refrigerant Flow (VRF) system to provide the same services. This study evaluated energy use by the GSHP and VRF systems, through bill analysis and on-site audits. We estimate the project saved 20 to 30 percent of energy use expected for water heating and space conditioning in typical new multifamily construction. However, the project team anticipated approximately double this level of savings. The shortfall appears to be primarily due to overly conservative heat pump controls with very low temperature set points for hot water.
Also presented in this report are lessons learned and best practices for designers of VRF and GSHP systems as well as for those tasked with measuring the energy efficiency of these custom projects. We recommend the elimination of circulation loops in systems using VRF water heating. Without detailed Measurement and Verification (M&V) data it is very hard to pinpoint or troubleshoot where excessive energy is being used. Pilot or demonstration projects for emerging technologies must be screened to ensure that the technology is appropriate for the project. Without trained staff in a position to monitor the system, new technologies will have a much lower chance of success.
Project Team
BPA: Jack Callahan and Robert Weber
2010 – 2014
​Additional Resources