Is VRF right for your next project?

Variable refrigerant flow (VRF) systems can be specified into a variety of buildings, especially those that require flexibility.

06/24/2015


Learning objectives

  • Understand where variable refrigerant flow (VRF) systems should be specified in nonresidential buildings.
  • Know the codes and standards that dictate their design.

Figure 1: With a VRF zoning system, the compact compressors and components can be installed in smaller indoor and outdoor spaces. These systems require less piping and duct space. Because VRF zoning systems use smaller VRF refrigerant piping, they give back space in the form of higher ceilings—contributing to Turner Construction’s goals of showcasing the original building. Courtesy: Mitsubishi Electric US Inc. Cooling & HeatingAccording to the 2014 HVAC and Building Automation Systems (BAS) Study conducted by Consulting-Specifying Engineer, the average annual dollar amount of HVAC and BAS products specified is $2.63 million. While this includes traditional products and systems—like air handlers, fans, and pumps—it also includes more nontraditional systems, including chilled beams and variable refrigerant flow (VRF) systems.

Building owners have the option to incorporate VRF systems into their buildings, and these “alternative” system manufacturers field many questions from interested engineers and building owners, though they may not be gaining momentum (see sidebar, “VRF market presents dilemma for engineers”). An overview of these systems and some best practices have been provided by Julianne Laue, PE, LEED AP BD+C, BEMP, senior energy engineer at the Center for Energy Performance, Mortenson, Minneapolis.

Question: Are there any best practices or tips you suggest for engineers considering VRF systems?

Laue: Analyze feasibility of VRF project selection based on energy-efficiency goals, building type, project type, climate, and building size.

Question: What types of projects lend themselves best to specifying VRF systems?

Laue: Any type of commercial construction projects that require high flexibility. Retrofit projects with low floor-to-floor heights are also prospects. Buildings with diverse, multiple zones requiring individual control—office buildings, schools, hotels—are all good candidates.

Question: What are the positive aspects of specifying VRF systems?

Laue: There are several: energy efficiency, design flexibility, quiet operation, ability for individual users to control temperatures, smaller ductwork, lightweight, and the ability to simultaneously heat and cool in zones on the same system.

Question: What are the negative aspects of specifying VRF systems?

Laue: Price per ton is higher than conventional systems, and long refrigerant lines and many fittings increase the potential for refrigerant leaks. There also is a need for supplementary heat in cold climates, and a need for a separate ventilation system.


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