Completion of the Goodman Acquisition

Daikin Industries, Ltd. announces the completion of its acquisition of Goodman Global Group, Inc. (Head Office: Houston, Texas, USA - hereinafter "Goodman"), which was announced on August 29, 2012, for a purchase price of 3.7 billion dollars (including the refinancing of Goodman's existing indebtedness) as of November 1, 2012 (US time). In the two months since the signing, Daikin obtained the regulatory approvals from relevant authorities necessary for consummating the acquisition.

Combining the state-of-the-art environmental technology of Daikin with the air conditioners of Goodman, Daikin plans to use this acquisition to launch advanced environmentally-friendly products in the US residential and commercial HVAC markets. In doing so, the company hopes to initiate a new wave of growth that sustains both business expansion and contribution to the environment.

Furthermore, Daikin hopes to improve competitiveness even further by capitalizing on Goodman's lean management know-how to develop business in emerging economies and high-volume markets and restructure the earning power of the Daikin Group overall, including activities in the advanced economies.

To quickly generate synergies between the companies while maximizing the advantages of the complementary relationship between Daikin and Goodman and accelerating further growth and development of both companies, we have begun formulating and implementing concrete action plans.

In regards to Daikin's consolidated financial results, the acquisition will be reflected in the consolidated balance sheet for fiscal year 2012 and in the consolidated income statement from fiscal year 2013.

Japan's Daikin to buy Goodman Global for $3.8 billion: source

Daikin to announce Goodman Global purchase Wednesday: Daikin source
Tue, Aug 28 2012


NEW YORK | Tue Aug 28, 2012 7:30pm EDT

(Reuters) - Japan's Daikin Industries Ltd (6367.T), the world's second-largest maker of air conditioners, has agreed to buy U.S. rival Goodman Global Inc from private equity firm Hellman & Friedman in a deal worth about 300 billion yen ($3.82 billion), according to a source familiar with the matter.

San Francisco-based Hellman & Friedman bought Goodman Global in October 2007 for $1.8 billion in cash, including $1.1 billion of its own capital. The transaction also included assumed debt and other financing for a total of $2.65 billion.

Hellman & Friedman declined to comment. Daikin could not immediately be reached for comment.

Daikin said in April 2011 that it had been pursuing Goodman but takeover talks were on hold due to Japan's devastating earthquake and tsunami. In January, Daikin reaffirmed that it was still interested in buying Goodman, but talks on a potential deal were on hold due to uncertainty over the global economy.

A deal would come more than two years after Goodman Global filed for an initial public offering in May of 2010. The company withdrew its IPO registration later that year, and a source at that time said it had explored a possible sale to Daikin and other potential buyers.

The deal marks a major push into the Americas for a company that was forecast to generate fewer than 10 percent of its projected 2012 air conditioning sales in the Americas, according to a May company presentation.

The Americas are the second-biggest market, behind Japan, for a Daikin business that provides refrigerants.

Daikin, which took over Malaysian-based O.Y.L. in 2006, has touted its ambition to become the world's biggest player in the heating, ventilation and air-conditioning sector (HVAC).

The company competes in a crowded field of providers of heating and cooling technology for residential and commercial use. Rivals include United Technologies' Carrier unit (UTX.N), Johnson Controls' (JCI.N) York, Lennox International (LII.N), and Ingersoll Rand Plc's (IR.N) Trane brand.

News of the deal was first reported by Nikkei.

($1 = $78.5000 Japanese yen)

(Reporting by Michael Erman, additional reporting by Soyoung Kim and Nick Zieminski,; Editing by Gerald E. McCormick and Richard Chang)

Performance Piece - ASHRAE HQ

ASHRAE HQ serves as a living lab for building efficiency, monitoring, and control

By:Jim Schneider



Donations of equipment, services, and furnishings from more than 20 companies, individuals, and the ASHRAE Foundation made the $7.65-million ASHRAE headquarters renovation possible. The total value of the donations was approximately $1.65 million.
Credit: courtesy ASHRAE

You can’t get very far in sustainable design without encountering the acronym ASHRAE. The Atlanta-based American Society of Heating, Refrigerating, and Air-Conditioning Engineers has written many of the performance standards used in green building. It is an organization leading the charge for better, more-efficient buildings.

The renovation of ASHRAE’s headquarters serves as a living laboratory for building-efficiency techniques. Outfitted with the latest monitoring and control technology, the ASHRAE headquarters provides a glimpse into the future of smart buildings.

Renovation for Innovation

In 2004, ASHRAE examined its headquarters and knew it had to make a change. “We evaluated many alternatives, including leased space,” recalls Bill Harrison, former president of ASHRAE and president of Little Rock–based HVAC firm Trane Arkansas. “However, we wanted to demonstrate the very latest heating, ventilation, air conditioning, and refrigeration technology, so our negotiations with leased space always broke down when it looked like we’d have to settle for a typical HVAC system. We wanted a real state-of-the-art system.”

The decision followed to renovate the existing facility. “Our first goal was to provide a healthy and productive workplace for our staff. We tried to keep that in mind whenever we, a bunch of technology wonks, got carried away,” Harrison recalls. “The second objective was to create a living laboratory where our members could learn something about how buildings truly operate.”

With the help of donated systems and equipment, the renovated facility incorporates a number of sustainable features. Ground-source heat pumps, variable refrigerant flow systems with heat recovery, and a dedicated outdoor air supply with energy recovery and humidity control provide considerable energy savings. “Compared with the old building, we now use less energy on a larger building with longer operating hours.”

In addition, using low-flow and no-flow fixtures throughout the building reduced water consumption by 52 percent. Indoor air quality also was a major point of emphasis; the outside air delivered to each space is 30 percent above minimum air-exchange rates specified in ASHRAE’s 62.1, “Ventilation for Acceptable Indoor Air Quality.”

“Some of our systems are innovative, but they’re also ones that are being used out in the real world,” Harrison asserts. “On one floor we’re using a variable-refrigerant-flow heat pump system. On the other floor we use a ground-coupled heat pump system where the heat pumps transfer heat energy from the building to the ground during the summer and pumps heat energy out of the ground and into the building during the winter. The entire building is served by a dedicated outside air unit that uses dual enthalpy wheels to reduce the humidity of the air being introduced into the building so that the building always operates at an acceptable humidity level.”


Sensors provided by Philadelphia-based Aircuity detect a broad array of indoor environmental parameters and work with the on-site building management system to create the best possible indoor environment.
Credit: courtesy ASHRAE

Lead by Example

In order to serve as a living laboratory, the building needed top-of-the-line monitoring and control systems to provide performance data. “It’s very difficult to communicate between so many systems,” Harrison says. “Consider that you have digital information streams coming from the heat pumps downstairs, the heat pumps upstairs, the dedicated outside air unit, the air monitoring system, the refrigerant monitoring system, and others. Our building automation systems vendor, Automated Logic, had to take all of those information streams and combine them into one.”

Not only were the data streams combined, in many cases they were tied into the control systems so it would be possible to operate the building on a minute-to-minute basis using fresh information. “One of the problems with monitoring is sometimes you’re overloaded with data,” Harrison says. “We hoped to use our automation system to filter some of that data.” The end goal was to generate digestible information, as well as continuous building optimization, from the raw data collected. For example, CO2 sensors in each room monitor the air quality and bring in outdoor air when specific set points are met. “There’s a certain amount of ventilation you need to take care of off-gassing from carpets, chairs, and furnishings, but then you need to increase that ventilation as people come into the room and give off CO2,” explains Steve Tom, director of technical information with Automated Logic. “That’s controlled by a CO2 sensor that adjusts the flow of the outdoor air into the room.”

Additional air-quality monitoring also is used in the building to establish a baseline and ensure the accuracy of the primary system. “We worked with a vendor that specializes in detailed air sampling. They have sensors throughout the building that monitor and make certain the air is being kept fresh,” Tom says. “It also tells you if a sensor is going out of calibration. If your primary system says the room is OK and the independent monitoring says it isn’t, you better take a look.”

A rooftop solar array consisting of 170-watt photovoltaic modules, donated by Atlanta-based Georgia Power/Southern Co., produces electricity during daylight hours and feeds energy back into the existing grid.
Credit: courtesy ASHRAE

Environmental Index

Monitoring often can be all about the data, which does play into the facility’s goal as a living laboratory. However, ASHRAE never loses sight of its other goal—providing a comfortable environment for its staff. “There’s another aspect to performance monitoring that’s fairly new. We call it an environmental index,” Tom explains. “We’re monitoring the temperature, CO2, and humidity, and compare those to building set points and an ideal range to come up with a numerical scale of 0 to 100, with 100 being ideal. This shows how well the system is working in terms of providing a comfortable and healthy environment for people. By assigning a numeric value to the environmental index, we easily can compare different rooms or we can ‘roll up’ the room indices to calculate the environmental index for an area or for the entire building. This also lets us compare indices before and after we change a control strategy to see how that change affects the people inside the building.”

As important as the raw data and installed efficiencies are, monitoring ultimately is a means to an end; and that end is a livable interior environment. “Everybody is looking at energy because that’s the cost of running the building. But if you cut back on energy to the point where you’re not providing a comfortable environment, people won’t get their work done. So what have you accomplished? There are all kinds of studies showing a direct link between comfort and productivity,” Tom asserts. “The key is energy efficiency—providing a healthy and comfortable working environment at the lowest possible energy cost. If you only monitor the energy and don’t monitor the environmental index, you’re only getting half the picture.”

The renovated ASHRAE headquarters officially re-opened in October 2008, but the monitoring systems are still a work in progress. “Preliminary data shows a 30 percent reduction in energy use. They still have to do some fine tuning, and some of the systems are just coming online now,” Tom says. “We’re monitoring all the meters and analyzing what is working and what needs to be optimized.”


A variable refrigerant volume system (VRV) serves the first floor and learning center. The non-ozone-depleting refrigerant, individual zone control capabilities and heat-recovery technologies all play a role in helping the facility meet its sustainability and energy goals.
Credit: courtesy ASHRAE

“We finally are getting close to having our electric meters fully calibrated so the data is completely accurate. There’s been a lot of shaking out we’ve been doing before we go public with a lot of the information,” Harrison says. “The problem we face as an industry is how to take the massive amount of data generated by a building and convert it into information so people can interpret that into knowledge. Frequently we get so much data it just clutters up the screen.”

Along with building systems, building occupants also are being monitored in a sense. ASHRAE conducts regular surveys to make sure people are getting the most out of the new space. “In the old building, if you didn’t have an office on the outer edge, you never saw the outside. In the new building, no one is where they can’t see exterior light,” Harrison says. ”Everything I’ve seen says our people like the way the building feels.”

Materials and Sources:Building management systems and services: Automated Logic, automatedlogic.com
Carpet: InterfaceFLOR, interfaceflor.com
Ceilings: Armstrong, armstrong.com
Concrete: Ready Mix USA, readymixusa.com
Flooring: InterfaceFLOR; Armstrong; Crossville, crossvilleinc.com
Furniture, seating: Allsteel, allsteeloffice.com
Glass: AGC
Gypsum, walls: National Gypsum Co., nationalgypsum.com
HVAC: Automated Logic; Climate Master, climate master.com; Daikin, daikin.com; Trane, trane.com
Insulation: Johns Manville, jm.com
Lighting control systems: Crestron, crestron.com
Lighting: Litecontrol, litecontrol.com; Zumtobel, zumtobel.us
Metal: WhiteHawk, whitehawkinc.com; Bec-Don, becdon.com; Gerdau Ameristeel, gerdauameristeel.com; MBA; Centria, centria.com
Paints and finishes: Pittsburgh Paints, pittsburghpaints.com
Partitions: Modernfold, modernfold.com
Pavers: Hanover Architectural Products, hanoverpavers.com
Photovoltaics: GE Energy, gepower.com
Plumbing, water systems: Rheem Manufacturing Co., rheem.com
Roofing: Firestone Building Products, www.firestonebpco.com
Sensors: Aircuity, aircuity.com
Siding: Centria Windows, curtainwalls, doors: YKK, ykkamerica.com; Glass Stream, glassstream.net; Vistawall, vistawall.com; Oshkosh, oshkoshdoor.com; Mesker Door, meskerdoor.com

Green teamArchitect; interior designer; lighting designer; green consultant, LEED consultant and/or life-cycle performance partner­: Richard Wittschiebe Hand (RWH), rwhdesign.com
Client/owner: ASHRAE, ashrae.org
Mechanical engineer: Johnson, Spellman and Associates, jsace.com
Mechanical contractor: Batchelor and Kimball, bkimechanical.com
Structural engineer: Diana D. Quinn
Electrical engineer: Jeffers Engineering Associates
Electrical contractor: Gene Lynn Electric
Commissioning agent: CxGBS, cxgbs.com
Civil/geotechnical engineer, landscape architect: AEC, aecatl.com
General contractor/construction manager: Gay Construction, gayconstruction.com

Variable Refrigerant Flow: An Emerging Air Conditioner and Heat Pump Technology

by
Ammi Amarnath, Electric Power Research Institute
Morton Blatt, Energy Utilization Consultant

ABSTRACT

This paper reviews the attributes of an emerging space conditioning technology; variable refrigerant flow (VRF) systems. Material presented in this paper was synthesized from the open literature, private interviews with industry experts and data (sometimes proprietary data) obtained from manufacturers. VRF systems are enhanced versions of ductless multi-split systems, permitting more indoor units to be connected to each outdoor unit and providing additional features such as simultaneous heating and cooling and heat recovery. VRF technology uses smart integrated controls, variable speed drives, refrigerant piping, and heat recovery to provide products with attributes that include high energy efficiency, flexible operation, ease of installation, low noise, zone control, and comfort using all-electric technology. VRF systems are very popular in Asia and Europe and, with an increasing support available from major U.S. and Asian manufacturers are worth considering for multi-zone commercial building applications in the U.S.

This paper provides an overview of variable refrigerant flow system technology, including the market situation, advantages and disadvantages for the customer, possible impact on the electric utility, applications recommendations, and technology attributes. Also addressed are what is holding back the technology, including lack of verified third party field data; codes and standards issues; technology improvements needed; and market actions needed to increase penetration of these systems.

Evolution of the Technology

[Continued...pdf]

VRV/VRF Variable refrigerant volume (or flow) technology

Published by the Air Conditioning and Heat Pump Institute, a section of the Institute of Refrigeration (U.K.)

Introduction to VRV / VRF

Variable Refrigerant Volume or Variable Refrigerant Flow (depending on manufacturer) has been around  or about a quarter of a century. The basic idea is that a large outdoor unit serves multiple indoor units. Each indoor unit uses an LEV (electronic liquid expansion valve) to control its refrigerant supply to match the demand of the space it serves. The outdoor unit also varies its output to match the communal demands of the indoor units it serves. Thus, at any point in a system there will be a variable volume of refrigerant flowing. Various strategies are used to vary the output of the outdoor units including; 

• Modulating fan/s

• Heat exchanger valved in sections

• Variable speed inverter drive compressor/s

• Multiple compressors

• Twin or multiple modular outdoor units

Outdoor unit capacities range from around 14 kW to over 100 kW. Indoor units cover the full range of DX models normally available.

System types

VRV/VRF systems can be used for cooling only, heat pumping and heat recovery. On heat pump models indoor units can be in either mode but all must be in the same mode if served by the same out door unit. The cooling only and heat pump models are basically large, sophisticated, efficient multi-splits. The heat recovery or simultaneous mode systems provide both heating and cooling from the same outdoor unit and thus exploit this technology most effectively. They offer considerable potential for energy savings in many applications.

[Continued...pdf]

Bonneville Power Administration: Variable Refrigerant Flow Overview

P R O J E C T   O V E R V I E W

June 2012

This Variable Refrigerant Flow (VRF) Overview discusses both the energy-efficiency considerations and the non-energy drivers for VRF systems, as well as information that was required for utility energy-efficiency incentives. Several case studies are included to demonstrate how these heating, ventilating and air conditioning (HVAC) systems benefited various buildings.


Background

Variable Refrigerant Flow (VRF) heating and cooling systems promise energy efficiency, flexibility and improved comfort in small to mid-sized commercial buildings. Traditional heat pumps have been evolving in Asia over the last thirty years, and VRF systems are now the preferred HVAC system for small and medium commercial buildings in both Asia and Europe.

 It is estimated that VRF systems condition over 50 percent of Japanese commercial buildings less than 70,000 square feet, and 15 percent of larger buildings.  VRF systems were introduced in the U.S. around 2002, and have been installed in many types of commercial buildings, including offices, hotels, luxury apartments, low-income multi-family buildings and universities. While VRF systems have the potential to save energy, very few have received utility energy-efficiency incentives in the Pacific Northwest, because of the difficulty quantifying and verifying VRF system energy savings.

[Continued...pdf]

MODELING AND EXPERIMENT ANALYSIS OF VARIABLE REFRIGERANT FLOW AIR-CONDITIONING SYSTEMS

by
Xuhui Wang, Jianjun Xia, Xiaoliang Zhang, Sumio Shiochi, Chen Peng, Yi Jiang
Department of Building Science, Tsinghua University, Beijing, China
Environmental Technology Lab., Daikin Industries, Ltd., Osaka, Japan

for

Eleventh International IBPSA Conference
Glasgow, Scotland
July 27-30, 2009



ABSTRACT

This study developed a component-based gray-box model for variable refrigerant flow (VRF) airconditioning systems to simulate and predict the performance and energy consumption of VRF system in cooling condition. Results from the testing of Daikin’s 10HP VRV system with six indoor units, as well as the manufacturer’s data, were used to fit the key parameters of each component in this VRF model. This model was integrated in the building energy simulation software DeST and was validated by using data both from Daikin’s product handbook and from tested results. The validation results showed that this model can be used to calculate the coefficient of performance (COP) of VRF systems in an error of less than 15%.

[Continued...pdf]

Mechanical System Modeling Guide Variable Refrigerant Flow (VRF) Systems

[Continued...pdf]

Operations Manual: VARIABLE REFRIGERANT FLOW MULTI-SPLIT AIR-CONDITIONERS AND HEAT PUMPS CERTIFICATION PROGRAM

PREFACE


The following manual outlines the procedures and policies of the Performance Certification Program for Variable Refrigerant Flow (VRF) Multi-Zone Air-Conditioners and Heat Pump Certification Program operated by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI). This manual is to be used in conjunction with the AHRI General Operations Manual for AHRI Certification Programs. Where the AHRI General Operations Manual and this product-specific manual differ, this product-specific operations manual shall prevail.

The revision of this manual supersedes all previous revisions. The current edition of this manual, as well as the AHRI General Operations Manual, can be accessed through the AHRI website, www.ahrinet.org. 

The AHRI VRF Certification Program by AHRI provides for independent verification of the performance of the Participant’s equipment. Safety criteria are not within the scope of this program.

Participation in the program is voluntary. Any manufacturer, regardless of AHRI membership, may obtain approval of Program Ratings and use of the AHRI VRF Certification Mark hereinafter referred to as the “Mark”. The Mark is the Participant’s public representation that the ratings of randomly selected units have been verified by an independent laboratory in accordance with test procedures prescribed by this operations manual. A Certification Agreement is executed between the manufacturer and AHRI specifying the conditions under which such Ratings and the Mark may be used. No manufacturer has the right to use Program Ratings or to state that their products have been tested in conformance with the procedures outlined in this Rating Procedure unless and until they have received written authority from AHRI to use the Marks as applied to the specific approved Program Ratings.

This Operations Manual has been prepared to assure that administration of the program is carried out in a uniform manner. It is an amplification of the license agreement signed by licensees and AHRI. General information, procedural details, and copies of forms are included in this Operations Manual. Provisions of the Operations Manual may be amended as provided in the Certification Agreement.

[Continued...pdf]

Variable Refrigerant Flow-Heat Recovery Performance Characterization

by
Walt Hunt, Harshal Upadhye, and Ron Domitrovic, Electric Power Research Institute
Paul Delany and Bach Tsan, Southern California Edison
Mira Vowles, Bonneville Power Administration


ABSTRACT
Anecdotal suggestion and manufacturer provided data provides evidence that variable
refrigerant flow systems with heat recovery  (VRF-HR) provide a significant opportunity for
building energy savings under certain conditions.  Actual operational data showing the
performance of heat recovery systems under varying conditions is scarce.  This paper details the
testing of a VRF-HR system under laboratory controlled conditions,  revealing operational
characteristics.  A four-zone VRF-HR system was tested at specified  conditions with varying
degrees of connected combinations of cooling and heating demand.  

Results show system power draw, delivered capacity, and EER are dynamic with changes
in total connected load, ratio of cooling to heating, and system net operating mode (net cooling /
net heating).  The results of this work inform VRF designers, model developers and energy
efficiency practitioners interested in pursuing VRF as an HVAC resource.

[Continued...pdf]

Impact of the Variable Refrigerant Volume Air Conditioning System on Building Energy Efficiency

by

Huawei Zhu

Zhejiang Urban and Rural Planning Design Institute,Hangzhou, China

Email：zhuhwky@163.com

Abstract: The application of the variable refrigerant

volume multi-zone air conditioning systems has met

with mixed results since the publication of the Design

Standard for Energy Efficiency of Public Buildings.

This paper analyzes the characteristics of the variable

refrigerant volume multi-zone air conditioning system,

and discusses the advantages of its application.

Key words: Design standard for energy efficiency of

public buildings, variable refrigerant volume air

conditioning system, energy efficiency of buildings,

application

[Continued ... pdf]

Savings from Variable Refrigerant Flow Systems

By Peter Criscione - Research Manager 

I’ve been studying heating and cooling technologies for many years, and variable refrigerant flow (VRF) systems are one of the more interesting efficiency opportunities that I’ve seen in a while. Instead of circulating conditioned air, VRF systems circulate refrigerant to multiple fan-coil units in the building. I’m often asked how they stack up against traditional heating and cooling systems. Unfortunately, I haven’t found an easy answer to this question—but some help is available. The main difficulty is that although these systems have an efficiency rating for both full- and part-load performance, these metrics don’t account for all of the technology’s capabilities. VRF systems can do simultaneous heating and cooling with heat recovery, a significant advantage over traditional systems. Some VRF heat pumps also perform better than traditional heat pumps at low outdoor air temperatures, and these systems can be configured with different numbers of indoor units. All of these factors make an apples-to-apples energy-use comparison with traditional equipment difficult at best.

To help evaluate VRF systems, a few options are available or emerging. The Consortium for Energy Efficiency (CEE) released a revised specification that, for the first time, includes VRF systems to guide utility program incentive levels for commercial air conditioning: CEE Commercial Unitary AC and HP Specification (PDF; effective January 6, 2012). Likewise, a new metric was developed for the VRF performance rating specification, ANSI/AHRI Standard 1230 with Addendum 1 (PDF), to account for simultaneous cooling and heating efficiency (SCHE). The Air-Conditioning, Heating, and Refrigeration Institute (AHRI) won’t be releasing SCHE data on manufacturer’s products for about another year, but when it becomes available it will help to differentiate the performance of the available VRF units. Also, the Bonneville Power Administration has just launched a field study in 10 buildings to attempt to capture the total heating, cooling, and ventilation system savings for VRF systems, but data will not be available for at least three years. Southern California Edison (SCE) is conducting a field test on one of its own buildings that should be completed this year.

To estimate savings from VRF systems compared to traditional air conditioners and heat pumps at this point, though, it seems that all roads are pointing to the need to do modeling. Currently, the EnergyPro software can model VRF units with heat recovery. In addition, the Electric Power Research Institute is working with several organizations, including SCE, to perform field and laboratory tests to develop performance maps for VRF systems that will be put into two other modeling platforms, eQuest and EnergyPlus, this year. Though not as quick as just comparing the energy-efficiency ratios of two rooftop units, these modeling tools at least provide designers a path to compare the savings from VRF systems to those of other options.

I’d like to hear your thoughts on variable refrigerant flow systems. If you’re using them, what savings are you seeing? Aside from the difficulty in estimating their savings potential, do you have other concerns with this equipment?

ASHRAE NB/PEI SEPT 2011: VARIABLE REFRIGERANT FLOW SYSTEMS Technology Overview

by

Roger Nasrallah, ing.
Enertrak inc.


VRF Presentation Contents
1. What is Variable Refrigerant Flow?
2. Why do we use VRF system?
3. How does VRF work?
4. VRF Indoor/Outdoor Units Capacity Control
5. Benefits of VRF Capacity Control
6. Different VRF Systems
7. Design Around Diversity
8. Comparing VRF to « Conventional Systems »

[Continued...pdf]

Does the application of Green Technologies always result in increased HVAC capital costs?

Variable Refrigerant Flow Systems – An Independent Case Study The continuous drive towards designing buildings and systems that significantly reduce our impact on the environment is pushing the innovation envelop within the HVAC industry. Does the application of ‘Green Technologies’ always result in increased HVAC system capital costs? Mitsubishi Electric is widely recognized as world leaders in the design and application of variable refrigerant flow systems for over thirty years. Even though such HVAC technology has been considered mainstream in both Asia and Europe for over twenty years variable refrigerant flow systems (VRF) are still considered by many as an emerging technology in both the United States and Canadian markets. Given this landscape conflicting or extremely limited market based information is currently available in Canada with regards to how the first costs of variable refrigerant flow systems compare with what is considered the more traditional four pipe chilled and hot water HVAC approach.   Variable Refrigerant Flow – The Concept Variable Refrigerant Flow systems control the amount of refrigerant flowing to individual indoor units. This allows for the use of multiple indoor units of varying capacity and configuration to one single condensing unit, resulting in simultaneous heating and cooling in different zones, with heat recovery form one zone to another. It is individual comfort control. Variable-speed-drive compressor technology (in the remote condensing unit) dynamically adjusts the system capacity to adapt to building load conditions, working in tandem with linear expansion valves at each indoor unit. The centralized control network ensures precise temperature control within each zone.

The Environmental Benefits The life-cycle environmental impact of any mechanical heating and cooling system is directly dependent on the carbon footprint of the energy source, as well as the total system performance characteristics – full and part load – in both heating and cooling modes. ARI studies indicate that a typical HVAC system operates at full load for only 1-2% of its life cycle. More detailed analysis illustrates that the majority of operating hours actually fall in the 40-80% total capacity range when in cooling mode. Mitsubishi Electric’s solution to optimizing system operation and reducing energy consumption is the variable refrigerant flow system that employ’s auto-tuning variable speed drive scroll compressors yielding high part load efficiency while also offering excellent seasonal energy efficiency. This performance optimization is achieved through dynamically matching daily or seasonal building load profiles. The ability to simultaneously heat and cool adjacent zones by energy transfer is another distinct advantage that the Mitsubishi Electric CITYMULTI VRF system has over other conventional approaches to HVAC design. An intermediate distribution compartment (BC Controller) facilitates the transfer of energy from the superheated refrigerant within the cooling zones to the refrigerant conditioning the heating zones. Where simultaneous heating and cooling are required the CITYMULTI variable refrigerant flow two pipe systems can transfer heat rejected from year round cooling zones (such as internal data rooms etc.) to perimeter zones which are calling for heating thereby reducing energy consumption. During shoulder season cycles, where simultaneously heating and cooling are more typical (east/west layouts, solar gain etc.), heat energy can be transferred between zones allowing the compressor to operate at part load (most efficient point of operation) while the indoor units are operating at full load (heating or cooling). Recently Mitsubishi Electric launched the ground breaking H2i Hyper Heating Inverter air-cooled product range which uses flash injection refrigerant circuits to secure 75% total heating capacity at -25 0C DB ambient temperatures with an efficiency rating of 1.5 COP – significantly higher than most conventional heating strategies. The Case Study Parameters The objective of this case study is to engage an industry recognized independent cost analysis team (AW Hooker – see profile for more details) to undertake a comprehensive first cost comparison through carefully considering the equipment costs, on site labor implications and commissioning costs for a range of HVAC system options as applied to  a high efficiency LEED certified commercial office building in Canada. The Evaluation Team AW Hooker Associates Ltd were founded in 1975 by Arthur W Hooker to provide superior quantity surveying and cost consulting services from an experienced and talented management team and staff of professional consultants. AW Hooker consultants use specialized knowledge, skills, and experience in a team effort in order to help clients make informed decisions at crucial stages in the development process of construction. For the purposes of this Case Study Mitsubishi Electric Canada worked with a senior consulting team led by Malcolm Yates (PQS CET) whose over 40 years of industry experience, including mechanical design consulting experience, proved invaluable during the development of this detailed case study. The Costing Analysis Technique Malcolm Yates and the team at AW Hooker employed the industry recognized elemental costing model to devise comparative cost estimates for multiple air conditions systems. A.W Hooker’s cost control process began with a deliberate gathering and extracting of all project information which might impact cost. The team worked to thoroughly understand each project’s requirements in order to properly interpret the design intent and application. This was followed with a methodical listing, tabulation and quantification process to which current market rates were applied. The result is a definitive cost report that compares the subject systems analyzed to the same level of costing parameters for a realistic and tangible comparative study. This can be relied upon as an objective, third party, independent report that tabulates and clearly identifies the costs of each system for comparative purposes The Building Template  The base building template for the case study is a 150,000 ft2 high tech, five storey office building designed to meet minimum LEED Gold standards. This building employs the world’s most innovative sustainable technologies to integrate its various internal systems into a highly efficient, cost effective working environment. The integrated systems offer the ability to monitor and micro-manage air quality, heating and ventilation, lighting, water usage and storm-water recycling. In this instance tenants will enjoy independent monitoring of their individual spaces to better regulate their specific needs. The Mechanical System Comparison The case study considered six mechanical heating and cooling system configurations for the template building as can be summarized in the following: Air-cooled Chilled Water System c/w VAV Distribution System Air-cooled Chilled Water System c/w Under Floor Air Distribution System Air-cooled Variable Refrigerant Flow System Water-cooled Chilled Water System c/w VAV Distribution System Water-cooled Chilled Water System c/w Under Floor Air Distribution Water-cooled Variable Refrigerant Flow System Heating loads are served by high efficiency gas fired condensing boilers except for the air-cooled variable refrigerant flow system where duct mounted supplementary heating elements are utilized. In the case of the water-cooled variable refrigerant flow system a reduced size of gas condensing boiler plant is provided to inject heat into the condenser water loop as required. The design cooling load for the building is approximate 375 tons and peak heating load 6000 MBH. Minimum ventilation air is provided by a standalone make up air unit with separate exhaust in each case to provide the ASHRAE recommended fresh air levels and air change rate within each conditioned zone. The Capital Cost Analysis The average installed capital cost for the air-cooled systems (chilled water and variable refrigerant flow system options) was estimated at $41.96 / ft2. The installed capital cost of the high efficiency air-cooled variable refrigerant flow simultaneous heating and cooling system was 5% lower than this average. Similarly the average capital installed cost for the water-cooled (chilled and variable refrigerant flow systems) was calculated at $44.96/ ft2. The installed capital cost for the high efficiency water-cooled variable refrigerant flow simultaneous heating and cooling system was typically within 10% of this value – the acknowledged margin of error attributed to the elemental costing technique. The on site commissioning cost for the two pipe simultaneous heating & cooling VRF air or water-cooled system was over 50% lower than the equivalent costs for any of the chilled water four pipe system design proposals. Capital Cost analysis is of course a fundamental initial consideration for any developer however building owners must adopt a long term perspective considering the life cycle impact initial capital cost driven design decisions can have. Life-Cycle Cost Analysis – A European Perspective  The most comprehensive real-world life-cycle analysis of variable refrigerant flow system performance come from Europe, where such technology has been considered mainstream for over 20 years. In 1998, an Italian bank, Unit Credit Banca, conducted energy retrofits on fourteen of its facilities. The capital projects team decided to retrofit 50 percent of the facilities with chiller/boiler four-pipe systems, and the remainder with VRF heating and cooling systems. Initial costs for both systems were similar, given the trade off’s between system design, on-site project management, mechanical infrastructure costs, and installation and commissioning time. Once in operational, the applications using the variable refrigerant flow systems consumed on average 35 percent less energy annually for heating and cooling. Annual maintenance costs were estimated to be 40 percent lower for VRF systems when compared to the chiller/boiler four pipe installations. Conclusion Comparing the total capital cost (equipment costs, installation and commissioning time on site etc.) of high efficiency innovative heating and cooling systems such as CITYMULTI variable refrigerant flow technology, to more conventional HVAC systems can offer a more definitive insight into the actual cost of ‘going green’ when applying mechanical HVAC systems to new build applications. CITYMULTI VRF technology can be applied to multiple building types and operations in both new and retrofit scenarios. Variable Refrigerant Flow systems yield significant operational cost benefits as well as capital cost parity or better. Going green is easier than you might think and Mitsubishi Electric are at the forefront in leading this shift in building system design as we continually strive to reduce our collective environmental impact.

Implementing Variable Refrigerant Flow Systems

Several Challenges And Opportunities Face HVAC Engineers When Implementing Variable Refrigerant Flow (VRF) Systems.

By Rodney V. Oathout, PE, CEM, LEED AP, Durrant, Phoenix and Dubuque, Iowa

11/30/2011


Variable refrigerant flow (VRF) systems are gaining popularity in the U.S. for cooling and heating in the built environment. These systems have real potential for contributing to the successful implementation of the Architecture 2030 challenge. The purpose of this article is to summarize the challenges and opportunities the consulting engineer faces when implementing VRF systems. The topics of design, ownership, and energy will be presented from the point of view of an engineering professional.

VRF systems combine a series of terminal units that come in many shapes and sizes with one condensing unit to serve the occupied space. These systems provide heating and cooling by circulating refrigerant between the terminal units and condensing unit. A device commonly referred to as a selector valve is used to manage refrigerant flow. An analogy is a water-source heat pump system. With a VRF system, there is refrigerant rather than water, and a selector valve dedicated device to direct the refrigerant. Condensing units can be air-cooled or water-cooled. Water-cooled systems can be coupled to a geothermal system to further improve performance. VRF systems, more than other HVAC systems, require interaction with manufacturer representatives to understand system capacities, specialties, and particulars related to system layout.

Design

VRF systems are filling a growing niche in renovation projects. The advantages inherent to VRF systems for renovations include smaller refrigerant pipelines and decorative indoor terminal units that can be installed in the occupied space. This allows the main components to fit in tight spaces common to renovation projects. For most projects, a lifecycle cost analysis is commonly used for guidance on selecting HVAC systems. The challenge for the design professional is to research the available simulation programs that can simulate VRF systems. On a level playing field, HVAC systems that cannot be readily compared to other HVAC systems are rarely selected for projects.

System layout for construction documents can be a challenge for design professionals. Most of the time, we are familiar with selecting components that can be built with minimal variation for the system intent. The manufacturers of VRF systems have many subtle (and some not so subtle) differences that lead to creative opportunities for presenting information. Differences like maximum pipeline length, maximum refrigerant lift, and unit capacities are manageable.

The challenge for engineers preparing bid documents include pipeline configurations (two or three pipes) and selector valve types that are critical to system operation. The objective of selector valves is to enable the terminal units to be in heating or cooling mode. Ultimately, maximum system operating flexibility occurs when one selector valve or circuit of a large selector assembly is matched with one terminal unit. Each terminal unit can provide heating or cooling without dependence on other zones. The electrical and condensate connections to the terminal units, selector valves, and condensing units should be coordinated in the design documents.

There are infinite strategies for combining multiple terminal units with selector valves to reduce the cost and maintain the performance of the system. In this arrangement, multiple terminal units connected to a single selector valve can only provide heating or cooling. VRF system information typically found on drawings includes terminal unit types, location, and capacity; other information must include system zoning with particular attention to selector valve and condensing unit relationships along with pathways for refrigerant piping and condensate. The rising cost of copper can be a driving force in the pipeline configuration that is a function of system zoning and is a critical element of the design and budget.

VRF systems are capable of managing most building HVAC loads. VRF equipment is available for dealing with building ventilation loads, but most projects are using a standard dedicated outside air system (DOAS) for access to features like energy recovery, humidity control, and other desired HVAC specialties. VRF systems typically perform well serving sensible loads but have minimal latent cooling capabilities. VRF systems, particularly air-cooled models, occasionally struggle to provide heat, especially in extreme winter conditions. To overcome this challenge, the DOAS also can be used as a supplemental source of heat to the building. The benefits of DOAS, including conditioning the ventilation air, controlling building humidity, and building pressurization, provide a good partnership with the VRF system. Some VRF systems also have the capability to capture refrigerant heat and direct it to a zone needing heat.

VRF control

There are many options to consider when selecting and interfacing building management systems (BMS) with VRF systems. Stand-alone systems with an interface station provided by the VRF manufacturer are popular, especially for smaller projects. There are multiple options and details with individual temperature control devices that should be investigated. Larger projects may use a BMS to monitor and provide some control of the VRF system. An analogy commonly used is VRF systems speak, which is a completely different language from most BMS systems used in the United States, so translators are used to aid this communication.

When a BMS is used with a VRF system, the manufacturer of the VRF system must provide a control system that actively manages all system components and translates information for the BMS. The BMS can be used for temperature setpoint adjustment, schedule, and other necessary activities communicating through the translator. Most VRF manufacturers do not permit control of the system by a third-party BMS. There can be two distinct control systems on a project, one provided by the VRF manufacturer and another by the BMS supplier, so it important to clearly define options and interfaces so all of the intended operations are met.

A tricky issue when implementing VRF systems is understanding the amount of refrigerant that ultimately exists in the system. It can be painful to learn that your building will have to be treated like a refrigerant machine room, according to ASHRAE 15, halfway through the construction process. The engineer should be aware of this issue when laying out the components and work with the manufacturer to estimate refrigerant quantities. The U.S. Green Building Council LEED Credit EA4 “Enhanced Refrigerant Management” and IEQ5 “Indoor Chemical and Pollutant Source Control” are usually not available when a VRF system is applied. Not to worry—there are lots of energy optimization points and other points available for projects seeking LEED certification.

Ownership

VRF systems have many technology features and specialties. There are a few simple guidelines for the engineer to enhance the value of the system for your client.

It is important to require specialized training for the installing contractor. Training should focus on installation details specific to the actual equipment being installed. There are a variety of differences among the VRF manufacturers. The equipment manufacturers of VRF systems understand the benefit of a well-trained installer since they typically require training and certification before the equipment can be purchased.

Commissioning to optimize the performance and reliability of the system is vital. Maintenance technicians trained in and experienced with refrigeration systems are key to long-term, successful operation of these systems. The backbone of these systems is refrigerant and controls. A technician with these skill sets can effectively troubleshoot and solve operational issues.

There are many terminal unit options for VRF systems. The most common arrangement has the terminal located in the occupied space. One benefit of this design is that the equipment is easily accessible. The risk is that room occupants may need to relocate for a period of time when system maintenance is performed.

Energy

The growing interest in building Energy Use Index (EUI), popularity of U.S. Environmental Protection Agency Energy Star, and emergence of the Architecture 2030 challenge proves that energy conservation and environmental stewardship are mainstream issues. VRF systems have much to contribute in the energy conservation category. While one of the challenges of VRF systems is developing an accurate energy simulation, this equipment has advertised energy efficiency ratios (EER) in excess of 20. VRF systems also promote diversity in the refrigerant system and sharing of energy between the terminal units. Space-by-space equipment distribution and nearly infinite compressor control promotes thermal comfort, and control features, such as enabling terminal units based on occupancy, promote efficiency.

Another way to determine energy consumption of VRF systems is to use an energy benchmarking protocol. Energy benchmarking is gathering actual energy use by building type, system type, and region. This energy data should be an integral part of the forecasting process used for many functions, including tuning the computer simulations.

VRF systems use electricity to provide heating and cooling so the energy ratio of your facility will be biased toward electricity. Impressive site EUIs can be expected with VRF systems, but depending on the region, the source EUI and resultant Energy Star score can suffer. Similar to other electric-intensive HVAC systems, control sequences should consider the utility rate structure.

VRF systems offer excellent opportunities for energy performance, system flexibility, and low noise dissipation. The design documents tend to be different, primarily due to the variety of technologies used by manufacturers. VRF systems are a legitimate option for an engineer’s high-performance tool kit. Hopefully, the issues raised by this article are useful to avoid common pitfalls and lead to successful projects.

Oathout is director of engineering for Durrant. He is an energy thought leader with a passion for collaboration, integrated design, and sustainability in pursuit of achieving the 2030 Challenge for the built environment.


VRF System Toolkit

Design

• Research energy simulation software suitable for VRF systems.
• Understand pipeline and selector valve options offered by different manufacturers.
• Clearly define zones and operating intent of the terminal units. The decision will have a substantial impact on system cost.
• DOAS usually make a good partner for the VRF system.
• How is the system going to be controlled—temperature set-back, ventilation, building pressurization, etc.?
• Define interface relationship for the VRF and BMS, if BMS is included.
• What is the correct amount of refrigerant in the building?
• Identify terminal unit style and capacity.
• Terminal units are not a good application for large volumes like gymnasiums.
• How will the condensate from the terminal units be collected?
• Certified Standard Ratings for equipment performance.

Ownership

• Require installer training and certification specific to actual equipment.
• Commissioning is vital.
• Maintenance technicians should be familiar with refrigerant components and systems.
• Terminal units are normally maintainable from the occupied space.

Energy

• Computer energy simulations can be a challenge.
• Consider using actual energy data from similar facilities/systems in your analysis.
• VRF systems only use electricity to provide heating and cooling.

New and Cool: Variable Refrigerant Flow Systems

Superior control and efficiency are bringing VRF systems to America

by Sara Fernández Cendón

Summary: Variable refrigerant flow (VRF) systems have been around for almost three decades, but they’re new to the U.S. HVAC market. As American engineers become familiar with the technology, and especially as they learn of its energy efficiency advantages, more in the industry might be willing to give the systems a try.


Cooling the old-school way

If you’ve been shopping for HVAC systems lately, you might have encountered a new contender among the usual choices. Introduced in the U.S. about five years ago, VRF systems were invented in Japan more than 20 years ago. They’re widely used not only in Asia, but also in Europe and South America.

VRF systems manufacturers highlight qualities such as energy efficiency, design flexibility for architects and engineers, quiet operation, and the ability the system grants individual users to control temperature in their own areas. Another appealing feature offered by most manufacturers is a centralized monitoring application that gives users control over the entire system from a single location or via the Web. The technology that makes it all possible is sophisticated, but VRF systems (also known as VRV, or variable refrigerant volume systems) are not very complicated.

A quick review of air-conditioning principles might be useful in describing VRF technology—the most basic principle, of course, being that air conditioning removes heat from the space to be cooled by pushing refrigerant through a cycle. The cycle comprises four elements common to all HVAC systems, which is based on the fluid dynamics that when a refrigerant expands, it becomes cooler; when it is compressed, it becomes warmer; and changing phases from fluid to gas or back again adds to the cooling/warming effect. So the system is composed of a compressor, a condensing unit, a metering device (or expansion valve), and an evaporator or heat sink.

In a direct expansion (DX) system, the simplest among air conditioning systems, the “hot” part of the cycle starts at the compressor, which compresses refrigerant vapor and turns it into a high-temperature gas. The refrigerant then goes through a condensing unit, a series of coils in which the gas loses heat and becomes liquid. The “cold” part of the cycle begins as the liquid refrigerant passes through the metering device, which causes a drop in pressure. The refrigerant then goes through the evaporator (another series of coils), and in the process of evaporating it absorbs heat from the surrounding area, producing a cooling effect that is dissipated through fans. After completing the cycle, the refrigerant goes back to the compressor in its initial low-pressure, gaseous state.

Slight variations in the refrigerant cycle have led to different applications designed for different uses. Window units, for example, pack all the elements of the cycle into one small device—the hot side being on the outside, the cool part facing the space to be cooled. Split-system units split the hot side of the cycle (placed outside the building) from the cold side (inside). In these types of systems, cool air is often transferred from the evaporator to many different rooms by an air-handling unit, which distributes the conditioned air through a series of ducts.

Industry standards set limits on the length of piping running between the condenser and the evaporator in DX systems. When the needs of a particular project exceed such limits, chilled water systems are often used as an alternative. In chilled water systems water is cooled by a regular refrigeration system and then circulated through ducts to air handlers throughout the building. Because there is no limit to the permitted length of water pipes, these systems are often used to cool large buildings or entire campuses. Chilling is often cycled at night to take advantage of off-peak energy rates.

The variable beauty of VRF technology
Configurations vary among the types of air-conditioning systems available, but one key ratio remains the same: always one condensing unit to one evaporator. For DX systems, this means that once a condensing unit is connected to an evaporator inside the building, providing cool air to several spaces requires either ductwork or additional condensing units and evaporators.

Not so with VRF systems, in which one condensing unit can be connected to multiple evaporators, each individually controllable by its user. Similar to the more conventional ductless multi-split systems, which can also connect one outdoor section to several evaporators, VRF systems are different in one important respect—although multi-split systems, like DX systems, turn on and off depending on whether the room to be cooled is too warm or not warm enough, VRF systems constantly modulate the amount of refrigerant being sent to each evaporator. By operating at varying speeds, VRF units work only at the needed rate, which is how they consume less energy than on/off systems, even if they run more frequently.

Although systems vary among manufacturers, VRF technology is usually available as heat pump or heat recovery units. Heat pumps provide either heating or cooling. Heat recovery systems allow for simultaneous heating and cooling—which means, for example, that one condensing unit might be connected to six indoor units, three of which could be used to cool some areas, and three of which could be used to heat other areas, all at the same time.

The modular nature of VRF offers a dizzying array of options. And, to help engineers interested in exploring the use of this technology, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has assembled a group to study VRF. ASHRAE included a description of the VRF system in its 2008 handbook on HVC systems and equipment and is now working on a separate chapter on VRF to be published in 2012.

Several manufacturers of VRF systems are part of the ASHRAE committee working on documentation for the technology, but only a handful are already marketing their systems in the U.S., with Mitsubishi Electric HVAC Advanced Products Division in Suwanee, Ga., and Daikin Industries (based in Osaka, Japan, with U.S. headquarters in Dallas) currently being the major players.

Both Mitsubishi and Daikin are taking steps to educate U.S. engineers, architects, and contractors on the technology. According to Meredith Emmerich, director of application support with Mitsubishi, about 10,000 people went through the company’s training on ductless and VRF systems last year alone. The company offers support and training through 1,100 locations across the U.S.

Daikin’s Dallas location, too, includes a training facility where VRF equipment is installed and exposed, so engineers, architects, and contractors may come in and see the outdoor and indoor units, the piping, the installation, and controls on all the models.

Breaking it down

VRF systems offer an energy-efficient solution that provides considerable flexibility. But, as with any other HVAC system, their cost-effectiveness and usefulness needs to be evaluated on a building-by-building basis. VRF systems are a good option for buildings with varying loads and different zones: structures such as hotels, schools, and office buildings where individual users want to have control over the temperature in their areas. VRF systems tend to have greater piping length allowances than DX systems and use copper piping with small diameters, which makes them suitable for buildings with low-ceiling spaces or for adaptive reuse and other projects aimed at preserving historic value with minimal destruction during installation.

Less likely candidates to benefit from VRF technology are large open volumes, such as gyms, theaters, or sanctuaries. These building types often fail to maximize the potential of the system, which is ideal for areas with different zones.

Lee Shadbolt, AIA, principal with Commonwealth Architects, based in Richmond, Va., says his firm is considering a VRF system for the renovation of Hotel John Marshall, a historic landmark built in the 1920s. Energy efficiency was one of the main factors considered, but there were other reasons to look at VRF.

“First, it’s a great application for multi-familiy residential use,” he says. “Second, it was extremely efficient and gave us a lot of points toward LEED certification. And third, it allowed us to work with the high-rise nature of the building.”

Shadbolt says other options (such as split systems or a central chiller boiler plant) have been considered for the project. But VRF, which is about 20 percent more expensive than other alternatives considered, is also significantly more efficient, according to his team’s assessment.

Regarding cost, Jami Billman, sales engineer with Daikin, says that VRF systems can be designed both in expensive and more affordable ways. For example, a system with one evaporator in every single room may be more costly initially, but the installation might require less ductwork. Or, in a different arrangement, several spaces might share a nearby evaporator. The smaller footprint of VRF equipment can also reduce costs. According to Billman, in most cases the system eliminates the need to have mechanical rooms, so useable space is given back to the client.

Joe Bush, application specialist for City Multi, Mitsubishi’s line of VRF systems, explains that Mitsubishi is the only manufacturer to use two refrigerant lines, instead of three, for heat recovery systems. He says this patented technology translates into considerable installation cost savings as well.

Ramez Afify, PE, LEED-AP, director of engineering at New York-based Clifford Dias Consulting Engineers, is a member of the ASHRAE group devoted to the study of VRF. In general, he estimates the initial cost of a VRF system to be 20 to 40 percent higher than a traditional split/heat pump HVAC system, but, he says, operating costs might be at least 10 percent less. According to Afify, the difference in price between a VRF and a conventional system might be recovered in fewer than five years.

Beyond the initial cost of VRF systems, disadvantages often cited revolve around refrigerant lines and ventilation. Afify explains that if VRF systems are large, as many chilled water systems are, a significant amount of refrigerant gas, instead of water, ends up running through the building.

“Of course refrigerant is not dangerous within certain volume limits, but if the system grows huge, it becomes a concern,” he says, adding that ASHRAE Standard 15, “Safety Code for Mechanical Refrigeration,” discusses the topic in detail.

Concerning ventilation, Afify explains that providing outside air can turn into a hurdle, because VRF units may require a separate ventilation system, especially in hot and humid climates or when dealing with high occupancy areas. Major manufacturers do generally offer outside air processing solutions that can be tied into the same control systems used for VRF units.

More than any of the above setbacks, however, Afify believes that what has kept U.S. engineers away from VRF systems has been a lack of familiarity and clear documentation. As more U.S. engineers become familiar with the technology, many in the industry expect to see VRF systems grow in popularity.

Variable Refrigerant Flow (VRF) Systems for Commercial HVAC

by
Bill Goetzler, CEM
Navigant Consulting, Inc.

[Power Point PDF]

Variable Refrigerant Flow

Preliminary Technology Assessment

What is This Technology?

Variable refrigerant flow (VRF) systems were invented in Japan more than 20 years ago, but new to the American market. VRF uses refrigerant as the cooling / heating medium, and allows one outdoor condensing unit to be connected to multiple indoor evaporators, each individually controllable by its user, while modulating the amount of refrigerant being sent to each evaporator.
 

Why is GSA Interested?

ENERGY EFFICIENCY.  By operating at varying speeds, VRF units work only at the needed rate. Heat recovery VRF technology allows individual indoor units to heat or cool as required, while the compressor load benefits from the internal heat recovery. Energy savings of up to 55% are predicted over comparable unitary equipment.

COST EFFECTIVENESS.  This product is new to the North American market, and most HVAC designers and installers are not familiar with the technology. Current estimates show an initial cost 20 to 40 percent higher than a traditional split/heat pump HVAC system, but with a payback that should be life cycle cost effective.

OPERATIONS AND MAINTENANCE.  VRF requires operations and maintenance consistent with other unitary equipment. VRF provides a greater degree of occupant control, which should improve occupant satisfaction with thermal conditions, typically the leading source of complaint.

APPLICABILITY.  VRF systems are designed to be modular, making them applicable to a wide variety of facilities as an alternative to other unitary equipment. VRF technology holds particular promise for GSA’s historic buildings because it relies on refrigerant piping, which requires fewer and smaller penetrations than other HVAC options, and enables the use of a large variety and configuration of inconspicuous indoor fan coil units.
 

Adapted from report by Pacific Northwest National Laboratory.
 

If you have questions or need additional information, contact the Green Proving Ground Program at GPG@gsa.gov.

The Green Proving Ground program leverages GSA’s real estate portfolio to evaluate innovative sustainable building technologies.

HVAC Variable Refrigerant Flow Systems Course

 No: M03-014

CED Engineering


Variable Refrigerant Flow (VRF) Systems

Variable refrigerant flow (VRF) is an air-condition system configuration where there is
one outdoor condensing unit and multiple indoor units. The term variable refrigerant flow
refers to the ability of the system to control the amount of refrigerant flowing to the
multiple evaporators (indoor units), enabling the use of many evaporators of differing
capacities and configurations connected to a single condensing unit. The arrangement
provides an individualized comfort control, and simultaneous heating and cooling in
different zones.

Currently widely applied in large buildings especially in Japan and Europe, these
systems are just starting to be introduced in the U.S. The VRF technology/system was
developed and designed by Daikin Industries, Japan who named and protected the term
variable refrigerant volume (VRV) system so other manufacturers use the term VRF
"variable refrigerant flow". In essence both are same.

With a higher efficiency and increased controllability, the VRF system can help achieve a
sustainable design. Unfortunately, the design of VRF systems is more complicated and
requires additional work compared to designing a conventional direct expansion (DX)
system.

This course provides an overview of VRF system technology.

[Continued...]

A Practical Guide to Multi-split Systems and Variable Refrigerant Volume (VRV) Systems

by Mike Hardy

This article is provided byAmbthair Services. If you are interested in Ambthair's air conditioning consultancy, design and installation services, please contact us.

Contents
Introduction
Multi-split Systems
Refrigerant Pipework Limitations
Indoor Units
Outside Air
Applications

Introduction

There are many manufacturers of multi-split systems and VRV systems throughout the world and it is important that the designer / specifier / building owner has some practical understanding of their uses and limitations. These type of systems vary considerably from manufacturer to manufacturer particularly with reference to noise levels and the type of indoor units used. This is particularly the case with VRV systems where it is often assumed, quite erroneously, that there are few manufacturers of these systems and they are all similar - this is not the case.

The above systems have come of age in the last 5-10 years and are particularly popular because they require less outdoor plant space than conventional systems, are less disruptive to fit in existing buildings (particularly when occupied), are able to cool and heat through common pipework and in the case of VRV systems have inherent heat recovery.

These systems all use refrigerant as the cooling / heating medium rather than chilled water / hot water as is used in conventional hydraulic systems circulated by pumps.

Condensing units are used externally when cooling only is required and heat pumps are used externally when both cooling and heating are required.

Multi-split Systems

The traditional ‘split system’ is also known colloquially and more descriptively as a 'one to one split system', meaning one external condensing unit / heat pump is connected by refrigerant pipework to one indoor cooling / cooling and heating unit.

The multi-split system uses one external unit which is connected to several indoor units. The multi-split system takes a number of different forms and it is essential the designer / specifier understands the limitations of each type of system.

Master and slave system

One off external condensing unit / heat pump unit is connected to several indoor units as is typical for a mult-split system. One of the indoor units is provided with temperature controller / sensor and acts as master and the other unit(s) acts as slaves. All indoor units will therefore function as the master setting. Master and slave units are suitable for single areas, single rooms or even multiple rooms with very similar heat gains / losses. They are not suitable for individual areas / rooms which have different heat gain / loss characteristics because the master control will sense air temperature for one area / room only and the areas / rooms will overcool or overheat.

Zoned control units

As previously one off external / heat pump unit is connected to several indoor unit. With these systems each indoor unit has its own individual temperature controller and thus each unit functions as required to maintain the individual room temperature. With these systems whilst there is individual control the limitation is that if cooling is required in one area it is not possible to provide heating in a different area served by the same system because the compressors will function in only cooling mode or heating mode.

Variable refrigerant volume (VRV) systems

Again one off condensing unit/heat pump is connected to several indoor units. VRV systems are able to provide total versatility and each indoor unit may cool / heat independently of each other. In fact, if part of a building requires cooling and other areas require heating the heat rejected for the required cooling contributes or is recovered to provide heating in the other area.

Refrigerant Pipework Limitations

The maximum lengths of pipework it is possible to use for all mass produced refrigeration equipment is determined by the the compressor. All ‘split’ systems therefore have a maximum vertical and total refrigeration pipework length allowable. This is a considerable disadvantage compared with hydraulic systems which are pumped and as the pump may be sized to suit the system, then theoretically, the hydraulic pipework may be run almost infinite distances. It is important the designer / building owner is aware of these limitations. Each manufacturer specifies both the size of the pipework required for their system and the maximum permissible vertical and total refrigerant pipework runs.

Moreover it may not be assumed that these distances will be similar between manufacturers for similar capacity equipment this is often not the case. However a nominal guideline is as follows:
Up to 5 kW of cooling maximum of 25 metres
Up to 7 kW of cooling maximum of 25 metres to 50 metres (varies widely between manufacturers)
Up to 15 kW of cooling maximum of 30 metres to 50 metres

VRV systems and zoned systems generally up to 50 metres vertically and 100mm overall. Typically one outdoor unit may be connected to up to a maximum of 8 indoor units.

(Some manufacturers produces a zoned system which allows up to 16 indoor units to be connected to one outdoor unit.)

Indoor Units

All indoor units used with multi-split systems provide air distribution by mixed flow and come in various forms:
Floor standing units
Units mounted on walls at high level
Unit mounted below a ceiling
Cassette units which recess within a false ceiling and terminate with a grille flush with the false ceiling through which air is supplied and exhausted to the space.
Ducted units or ‘void pack’ units mounted above a false ceiling and are generally connected to ductwork terminating in the ceiling with supply and exhaust grilles to the space. These ducted units may take the form of ‘low static’ pressure units or ‘high static’ pressure units.

With reference to (e), the size and type of the fan motors in these units vary considerably from manufacturer to manufacturer and this determines the extent of the ductwork allowable which is a function of the static pressure of the fan. Silencers may also be provided within the ductwork for very low noise levels required in such spaces as recording studios, but again the fan static pressure available has to be checked carefully so the pressure drop through the silencers may be overcome by the fan.

Outside Air

The introduction of outside air to all ‘split’ systems is often a problem (typically 8 L/S per person is required). To overcome this some manufacturers provide a heat recovery unit which provides outside air to the air conditioned space independently of the indoor units. With these systems an equal quantity of outside air and exhaust air is supplied and then exhausted from the air conditioned space. The supply and exhaust air passes over a heat exchanger so heat is recovered from the exhaust air and used to heat or cool the outside air. This solution has the limitation that air is introduced to the space at two different temperatures, i.e. that of the indoor unit and that of the heat recovery unit. If possible it is always ideal to introduce outside air to the indoor unit. It is possible to introduce outside air to the following indoor units:

Cassette units

Some manufacturers provide cut outs on the side of the unit so outside air may be ducted into the side of the unit above the false ceiling. The length of the outside duct has to be carefully considered and if over a certain length may have to be fan assisted. Most manufacturers publish maximum permissible lengths and / or pressure drops. As the outside air will bypass the cassette filter the ductwork should also be provided with a filter.

Ducted unit

Provision may always be made for introducing outside air into the return air ductwork.

Applications

The application of multi-split, zoned and VRV systems should be carefully considered. Whilst the VRV systems are the most versatile the capital outlay for the equipment is far higher than for the other systems.

Multi-split and zoned systems

With most of these systems generally it is possible to provide individual control to each indoor unit (the exception being the master and slave system previously described). The sensor will provide cooling or heating as and when required to maintain the set point temperature selected.

The systems are therefore applicable when there is a clearly defined heating and cooling season i.e. cooling only required throughout the building or heating only required throughout the building. With the increased prevalence of heat producing I.T. equipment within buildings this needs some consideration because if one particular part of a building requires cooling 12 months of the year this system would not be appropriate. The solution in this case would be either to use a V.R.V heat recovery system or have an independent system dedicated to that part of the building.

With the larger zoned systems typically it would be possible to connect up to 16 indoor units to one external unit. With most manufacturers the units may be mixed i.e. an assortment of ducted, cassette, wall, floor, and ceiling units connected to the one outdoor unit.

VRV systems

These systems are the most versatile of the multi-split systems as the indoor units may function individually and will heat or cool individually. These systems are widely used in commercial offices.

This article is provided by Ambthair Services. If you are interested in Ambthair's air conditioning consultancy, design and installation services, please contact us.

School Receives One of the US' Largest VRF A/C Retrofits

VRF A/C installation with cost-saving rooftop equipment mounts saves school more than 30% vs. standard A/C.

When a school such as the 85-year-old West View Elementary needed an air-conditioning retrofit, some engineers would have taken the path of specifying conventional rooftop package units, curb and rail mounts, and metal ductwork.

However, the Pittsburgh, PA-based North Hills School District hired BDA Engineering Inc. to think outside the box and take the specification path less traveled by considering energy efficiency, job costs, installation expediency and indoor air comfort.

Gary Albert, P.E., LEED AP, a BDA associate and project leader, specified 290 tons of cooling via 28 rooftop VRF heat pumps ranging from six to 24 tons—one of the U.S.'s largest VRF projects. VRF technology helped eliminate ductwork, roof penetrations and curbs, and provided optimum indoor air comfort control to individual classrooms, while causing minimum disruption to the school's daily schedule.

Albert estimated the VRF system saves the school 30%–50% or more in yearly energy savings vs. a chiller system and a variety of "ducted non-VRF" systems, respectively. Additionally, $50,000 or more was saved on the $2.3 million project due to the rooftop equipment mount specification.

Design team members included construction manager Thomas & Williamson and HVAC wholesaler Comfort Supply Inc., which provided technical design configuration and installation assistance with the prefabricated rooftop mounting systems by Big Foot Systems represented in the U.S. by RectorSeal Corp. Comfort Supply also provided factory-certified design and start-up assistance with City Multi VRF equipment manufactured by Mitsubishi Electric Cooling & Heating.

Equipment mount savings

Equipment mounts were one of the most significant value-engineered specifications. Instead of two 4-ft-long rails with roof-piercing flashing for each of the 28 heat pumps, BDA specified more than 180 linear ft of Big Foot Systems equipment mounts. The strategy eliminated the need for a roofer and general contractor, saving tens of thousands of dollars in labor costs. While Big Foot Systems has been used worldwide for large projects such as the British Airport Authority's Heathrow Airport terminal rooftop A/C equipment, the West View project is one of the largest U.S. Big Foot Systems projects to date, according to RectorSeal spokespeople. The project was also the largest VRF project for Comfort Supply.

"Using VRF and combining it with this type of equipment mounting is a big trend the last few years due to the quick installation, energy efficiency and LEED aspect," said Justin Kern, Commercial Sales Manager, Comfort Supply.

In addition to roofing labor savings, the project's mechanical contractor, R&B Mechanical, was able to bolt the individually identified equipment mounting components together in considerably less time than setting conventional rails, according to Thomas Recker, Vice President, R&B Mechanical.

The mounting system, which consists of 1/6-sq-in., corrosion-resistant, hot-dipped galvanized tube modules, sits 18 in. above the roof surface using 1-sq-ft, glass-filled nylon footings with anti-vibration mat bases. Matching footings specifically designed for utility piping were also used for electrical, refrigerant and control wiring piping runs across the roof.

Not making dozens of roof cuts for equipment rails also eliminated concerns about potential leaks to an older-style roof built 85 years ago. Future roof resurfacings will not require heat pump and piping disconnections because there are no roof penetrations, therefore one leg at a time can be removed and temporarily supported to provide access to the roof membrane below.

HVAC equipment selection

BDA considered many options before arriving at the VRF. Solutions such as chillers to supply the existing unit ventilator system in every classroom, or DX conventional rooftop systems with ductwork, were considered too costly, not as efficient and disruptive for the school. Instead, the project used Mitsubishi Electric CMFR-Series, 100% outdoor air VRF heat pumps and air handlers combined with the school's existing room ventilator exhaust fans to pressure balance the system. Additionally, Y-Series heat pumps supply mixing boxes that distribute cooling to classroom wall-mounted or ceiling-cassette fan coils.

"No classroom or space receives re-circulated air from another space," said Albert. "This will improve indoor air quality, which is proven to have a direct effect on reducing student absenteeism due to illnesses."

BDA's design also optimizes energy savings during the fall and spring by using the 100% outdoor air system as an economizer strategy and/or heat pumps for heating with a BACnet-based building automation system by Andover Controls—division of TAC, and installed by Combustion & Service Equipment Co. The VRF system monitors and controls itself, but also feeds data to the BAS for a total HVAC overview. The energy savings climbs significantly during the off-season when heating and cooling might be needed simultaneously throughout the school in various spaces, according to Albert.

“From my standpoint, the potential for such a high level of individual cooling (and heating during seasonal transition) control per space can't be accomplished with other concepts," said Albert.

When a roof can't handle rails

The prefabricated equipment mounting systems also made certain placements on less fortified roof areas of the West View Elementary school possible.

"Rails would have spanned across structurally weaker parts of the roof whereas the footings were positioned only on the strongest parts of the roof steel," said Albert.

The Big Foot Systems supporting several heat pumps atop the less-fortified gymnasium roof were instrumental in space framing and weight distribution. Because only certain far-spaced steel roof joists could support the weight of heat pumps, the equipment mounting was designed and assembled to position and span the footings out to the strongest joist points, regardless of the equipment's small footprint.

For more information, visit www.rectorseal.com.