Engineered Systems - February 2008 - (Page 60) Variable Refrigerant Flow it with the VRF is not recommended except in dry climates where condensation will not create moisture problems. Heat recovery ventilators can be used to reduce cooling loads on the VRF units. Both water cooled and air cooled systems are available, as well as systems integrated with ice storage units. WHAT PERFORMANCE SHOULD I EXPECT? Data from a VRF manufacturer compared installation and operating costs for a set of 14 branch buildings in central/northern Italy where a chiller/boiler system was installed in seven of the buildings and a VRF system was installed in the other seven buildings (designed to handle heating down to -20°C [-4°F]) in 1998. The VRF systems used 35% less energy and had 40% lower maintenance costs for the period studied. As suggested by other manufacturers, the equipment costs for the VRF systems were higher than the equipment costs for the chiller-based systems but this was offset by lower installation costs for the VRF systems. Information obtained in discussions with another manufacturer suggests that their VRF systems could save up to 30% to 40% of the energy used by a chiller-based system for a 200-ton cooling system for a generic commercial building. The same data set indicates that the installed cost of a VRF system will be about 8% more than a water cooled chiller and 16% more than an air cooled chiller. Combining these energy use and installed cost projections provides an estimated payback period of about 1.5 years for the VRF compared to an air cooled chiller, and about 8 months compared to a water cooled chiller. Anecdotal information exists (Roth et al. 2002) showing savings of 38% in a side-by-side comparison with a rooftop VAV installation, but this study compared a new VRF system to the existing rooftop VAV system. Simulation results for a Brazilian climate showed savings of over 30% in summer and over 60% in winter. Savings of 5% to 15% were suggested to be more likely in the U.S. A modeling study conducted with a version of EnergyPlus that was modified to simulate VRF systems showed that, in a 10-story office building in Shanghai, a VRF system saved more than 20% of the energy compared to a VAV system and more than 10% compared to a fancoil plus fresh air system (Zhou et al. 2006). Installed costs are highly dependent on the application, construction, and layout of the building and whether the installation is new or retrofit. Lack of familiarity with the technology in the U.S will add to VRF costs. Total costs for VRF systems are likely to be about 5% to 20% higher than chilled water systems of similar capacity (Roth et al. 2002) One manufacturer provided verbal information that VRF systems cost about 30% to 50% more than equivalent capacity singlepackage ducted systems with SEER of 13 to 14. And that VRF systems cost more than twice as much as packaged terminal units. This information is interesting but not as important as the comparisons of VRF and chiller systems if VRF manufacturers position their product as a chiller alternative. Cost and energy use are highly application-dependent and should be obtained from detailed analysis and corresponding rigorous laboratory and field testing of multi-split systems. The need for this information currently exists for applications in the U.S. WHAT ARE THE BEST APPLICATIONS FOR VRF SYSTEMS? Initial applications of VRF in commercial buildings have included building add-ons such as a new data centers and situations where spot cooling is needed. Historical buildings have benefited from the minimum alterations needed for the addition of a VRF system. Retrofit situations where air conditioning may be an addition/upgrade to the space can be good applications of ductless systems since additional ductwork and conditioning needed for ventilation can be minimized with VRF systems compared to ducted systems. Other applications well-suited to VRF systems include anywhere there is an advantage to delivering personalized, compartmentalized comfort conditioning, such as office buildings, strip malls, and hotels and motels. Hospitals and nursing homes can be good candidates as well, since the VRF system makes it easy to avoid zone-tozone air mixing. Banks have favored the system for security because the egress paths into the bank are minimized due to the minimal smaller diameter ductwork. Even in schools, which often, due to high occupancy, have a 100% outside air requirement, VRF units can be used (often with heat recovery ventilators) to meet the load. VRF systems can also be used in luxury single-family homes as well as in condos and multi-family residential buildings. ES Amarnath is a senior project manager/technical leader in the Energy Utilization program area of the power delivery and markets sector of the Electric Power Research Institute. His research activities also include demand response and dynamic energy management – a dynamic, integrated systems or networked perspective that simultaneously addresses electric energy savings, demand reductions, and peak load management for the industrial, commercial and residential sectors. Reach him at aamarnath@epri.com. Blatt is an energy utilization consultant based in Mountain View, CA, and has over 30 years experience in commercial building energy efficiency research. His consulting projects have included research on advanced space heating and cooling technology for the DOE, California Energy Commission, and the Electric Power Research Institute. He is an ASHRAE fellow and is active on several ASHRAE Technical Committees. He can be reached at mhblatt@earthlink.net. REFERENCES Dyer, Mark, “Approaching 20 years of VRF in the UK,” Modern Building Services, June 2006, http://www.modern-building-services.co.uk/news/fullstory.php/aid/2127/Approaching_20_years_of_VRF_in_the_UK.html. Goetzler, William, “Variable Refrigerant Flow Systems,” ASHRAE Journal, April 2007, http://txspace.tamu.edu/bitstream/1969.1/5546/1/ESL-IC-06-11-80.pdf. Johnson, Spellman, “ASHRAE Headquarters Building Renovation, Mechanical Systems Narrative,” June 26, 2007, http://images.ashrae.biz/renovation/documents/06js22_ mech_design_narrative_permit%20set_2.pdf. Roth, Kurt, et al. “Energy Consumption Characteristics of Commercial Building HVAC Systems Volume III: Energy Savings Potential,” TIAX LLC for DOE, 2002, http:// doas-radiant.psu.edu/DOE_report.pdf or www.eere.energy.gov/buildings/info/documents/ pdfs/hvacvolume2finalreport.pdf. Smith, Lee, “History Lesson: Ductless Has Come a Long Way,” The ACHR News, April 30, 2007. 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