Print this page Print this page

Variable Refrigerant Flow

Lee Layton, P.E.


Course Outline

The course begins with a discussion of energy consumption in commercial buildings and how VRF systems may be used in commercial buildings.  Chapter 1 is a simple tutorial on how a traditional heat pump system works.  Chapter 2 explains how a VRF system works and the different configurations of VRF systems.  Chapter 3 is a case study conducted by the U.S. GSA and the results of that study.  Chapter 4 is an in-depth look at how and when to use VRF systems and the advantages and disadvantages of these systems.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

After taking this course you should,

Intended Audience

This course is intended engineers and architects and facilities managers who want to use the most efficient HVAC system for their commercial buildings.

Benefit to Attendees

After taking this course you will know how VRF systems work and the best building applications for VRF systems why a VRF system may be the correct choice for a given application.

Course Introduction

Commercial buildings account for approximately 40% of the energy consumption in the United States. About a third of commercial building energy usage is for heating, cooling and ventilation. 

One HVAC technology that is in common usage outside of the United States and beginning to enter the U.S. market is variable refrigerant flow (VRF) multi-split systems. These systems are also referred to as variable refrigerant volume (VRV) systems. VRFs are packaged outdoor compressor units connected through refrigerant lines to multiple refrigerant fan coil units in the building. 
 
Variable refrigerant flow (VRF) heating, ventilation, and air conditioning (HVAC) systems are one possible tool to improve energy efficiency. They are the primary HVAC system choice in Europe, Japan, China, and other parts of the world. VRF is particularly appropriate to existing buildings that use excessive energy or need HVAC repair and upgrade for other reasons. 

VRF has about 24% of the global commercial air conditioning market, and over 35% market share in China, India, the European Union, and Eastern Europe. The VRF share of the U.S. market is still only about 3%, but multiple manufacturers sell these systems in the U.S. and sales are growing. These manufacturers provide the products through an integrated supply system, including installation and design training, and sometimes provide part or all of the design, as well as quality control.

The U.S. market has been slower to accept VRF technology for several reasons. In Europe, many buildings did not have air conditioning, and adding ductwork was expensive or nearly impossible given space constraints. Europe has tended to provide cooling with chilled water fan coils rather than ducted systems. The United States has a long history with ducted HVAC systems using both direct expansion (DX) systems and chilled water systems..

VRF systems use refrigerant lines to distribute the refrigerant throughout the building, and since VRF systems use more refrigerant than direct expansion systems this raises concerns about leaks and compliance with ASHRAE Standard 15 Safety Standard for Refrigeration Systems which regulates refrigerant safety and environmental and sustainability impacts. 

Course Content

This course content is in the following PDF document:

Variable Refrigerant Flow

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

You may need to download Acrobat Reader to view and print the document.


Course Summary

Variable Refrigerant Flow system technology has successfully demonstrated itself outside the U.S., where it dominates the HVAC market in many countries. The U.S. market has been slower to respond, but interest is growing. The systems offer energy saving, comfort control, flexibility, and ease of installation in existing buildings. 
 
Reasonable estimates for HVAC energy cost savings are around 30% for VRF as an alternative to existing systems across a broad range of buildings, system types and climates. The incremental costs of using VRF systems are relatively high, and opportunity for a reasonable payback is limited for the average or less than average building energy usage.

VRF should be targeted at existing buildings with high energy bills, need for HVAC upgrades or cooling expansion with limited room for ductwork changes, climates with significant heating loads, particularly where VRF can replace VAV systems with electric reheat or other electric heat, and buildings with multiple spaces that would benefit from independent temperature control. New buildings to target include projects with a high-performance design objective and budget to support it, buildings that can take advantage of the potential to reduce floor-to-floor height, and the avoidance of more expensive controls and monitoring that may be included with VRF systems. 

VRF systems are most cost-effective when matched with applications and climates that offer the best value given the typically higher initial cost of the systems.   The items to consider include operating costs, project type, building type, building size, and climate.
 
Targeted VRF projects can provide a reasonable energy cost savings and simple payback. Higher maintenance, repair and replacement costs relative to some other system alternatives can offset much of the energy cost savings, and these costs should be evaluated when deciding whether or not to use VRF systems. VRF systems should be compared with other high efficiency HVAC alternatives during early design, and between operating buildings with different HVAC systems. 

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.