PREFACE This second edition represents a major update and revision of the ASHRAE Air-Conditioning System Design Manual. The request that drove this revision effort was simply to make a success- ful resource more current. The revision process involved a thorough editing of all text in the manual, the addition of SI units throughout, the updating of references, and the editing of many illustrations. New material dealing with design process, indoor air quality, desic- cant dehumidification, and “green” HVAC&R systems was added. The editor acknowledges the active assistance of a Project Monitoring Subcommittee (with Warren Hahn as Chairman) from ASHRAE Technical Committee 9.1, which supervised the revision of this manual. The editor and committees are grateful to several individuals who reviewed all or parts of the draft of this revision and made valuable suggestions for improvements and clarifications (see list of contributors). Andrew Scheidt, University of Oregon, provided graphic assistance for the editing of many illustrations. Walter Grondzik, PE, Editor ix ACKNOWLEDGMENTS LIST OF CONTRIBUTORS Final Voting Committee Members Dennis J. Wessel, PE, LEED John L. Kuempel Jr. Karpinski Engineering, Inc. Debra-Kuempel Stephen W. Duda, PE Kelley Cramm, PE Ross & Baruzzini, Inc. Integrated Design Engineering Rodney H. Lewis, PE Associates Rodney H. Lewis Associates, Inc. John E. Wolfert, PE Howard J. McKew, PE, CPE Retired RDK Engineers, Inc. Phillip M. Trafton, VC Mark W. Fly, PE Donald F. Dickerson Associates AAON, INc. Hollace S. Bailey, PE, CIAQP Gene R. Strehlow, PE Johnson Controls, Inc. Bailey Engineering Corporation Lynn F. Werman, PE Charles E. Henck, PE, LEED Self-Employed Whitman, Requardt & Associates Harvey Brickman K. Quinn Hart, PE Warren G. Hahn, PE US Air Force Civil Engineer CEO, Hahn Engineering, Inc. Support Agency William K. Klock, PE John I. Vucci EEA Consulting Engineers, Inc. University of Maryland xi Other Major Contributors and Reviewers (Only major reviewers and contributors are listed. The committee is very thankful to numerous individuals who freely gave their time to review special parts of this manual.) Charles G. Arnold, PE Arthur D. Hallstrom, PE HDR One Company Trane Rodney H. Lewis, PE David Meredith, PE Rodney H. Lewis Associates Penn State Fayette, The Eberly Joseph C. Hoose Campus Cool Systems, Inc. James Wilhelm, PE Paul A. Fiejdasz, PE Retired Member ASHRAE John G. Smith, PE Hank Jackson, PE Michaud Cooley Erickson Con- Member ASHRAE sulting Engineers William G. Acker Chuck Langbein, PE Acker & Associates Retired A special thanks to John Smith, David Meredith, and Chuck Langbein, who reviewed and commented on each chapter through all revisions. Warren G. Hahn, PE, TC 9.1, Air-Conditioning System Design Manual Update and Revision Subcommittee Chairman xii CHAPTER 1 INTRODUCTION 1.1 PURPOSE OF THIS MANUAL This manual was prepared to assist entry-level engineers in the design of air-conditioning systems. It is also usable—in conjunc- tion with fundamental HVAC&R resource materials—as a senior- or graduate-level text for a university course in HVAC system design. This manual was intended to fill the void between theory and practice, to bridge the gap between real-world design practices and the theoretical knowledge acquired in the typical college course or textbook. Courses and texts usually concentrate on theoretical calculations and analytical procedures or they focus upon the design of components. This manual focuses upon applications. The manual has two main parts: (1) a narrative description of design procedures and criteria organized into ten chapters and (2) six appendices with illustrative examples presented in greater detail. The user/reader should be familiar with the general concepts of HVAC&R equipment and possess or have access to the four-volume ASHRAE Handbook series and appropriate ASHRAE special publi- cations to obtain grounding in the fundamentals of HVAC&R sys- tem design. Information contained in the Handbooks and in special publications is referenced—but not generally repeated—herein. In addition to specific references cited throughout the manual, a list of general references (essentially a bibliography) is presented at the end of this chapter. The most difficult task in any design problem is how to begin. The entry-level professional does not have experience from similar projects to fall back on and is frequently at a loss as to where to start a design. To assist the reader in this task, a step-by-step sequence of design procedures is outlined for a number of systems. 1 2⏐ INTRODUCTION Simple rules are given, where applicable, to assist the new designer in making decisions regarding equipment types and size. Chapter 2 addresses the difference between analysis and design. The chapter covers the basic issues that are addressed dur- ing the design phases of a building project and discusses a number of factors that influence building design, such as codes and eco- nomic considerations. Human comfort and indoor air quality, and their implications for HVAC&R systems design, are discussed in Chapter 3. Load calculations are reviewed in Chapter 4. The specif- ics of load calculation methodologies are not presented since they are thoroughly covered in numerous resources and are typically conducted via computer programs. HVAC&R system components and their influence on system design are discussed in Chapter 5. Chapters 6 through 8 cover the design of all-air, air-and-water, and all-water systems, respectively. Here, again, a conscious effort was made not to duplicate material from the ASHRAE Handbook— HVAC Systems and Equipment, except in the interest of continuity. Chapter 6 is the largest and most detailed chapter. Its treatment of the air side of air-conditioning systems is equally applicable to the air side of air-and-water systems; thus, such information is not repeated in Chapter 7. Chapter 9 covers a variety of special HVAC&R systems. Controls are treated in Chapter 10. The appendices contain detailed descriptions and design calcu- lations for a number of actual HVAC&R-related building projects. They serve to illustrate the procedures discussed in the main body of the manual. The projects in the appendices were chosen to cover a variety of building applications and HVAC system types. They help to give the entering professional a “feel” for the size of HVAC&R equipment, and they indicate how a designer tackles par- ticular design problems. Since these examples come from actual projects, they include values (such as thermal properties, utility costs, owner preferences) that are particular to the specific contexts from which they were drawn. The purpose of the examples is to show process, not to suggest recommended or preferred outcomes. A few words of advice: do not hesitate to make initial design assumptions. No matter how far off the specific values of a final solution they might prove to be, assumptions enable the designer to start on a project and to gradually iterate and improve a proposed design until a satisfactory solution has been obtained. Frequently, more experienced colleagues may be able to assist by giving coun- sel and the benefit of their experience, but do not hesitate to plunge ahead on your own. Good luck! AIR-CONDITIONING SYSTEM DESIGN MANUAL⏐3 1.2 HOW BEST TO USE THIS MANUAL The following suggestions are made to obtain maximum bene- fit from this manual: 1. Consider the general category of the building being designed and read the appropriate chapters in the ASHRAE Handbook— HVAC Applications and the ASHRAE Handbook—HVAC Sys- tems and Equipment to determine likely systems to consider for application to the project. 2. Familiarize yourself with the theory and basic functions of common HVAC&R equipment. The best sources for this information are HVAC&R textbooks and the ASHRAE Hand- book series. 3. Read the chapters in this manual that address the systems of interest. 4. Review the example problems in the appropriate appendices of this manual. 5. Become familiar with state and local building codes, ASHRAE standards and guidelines, and applicable National Fire Protec- tion Association (NFPA) resources. Remember that this manual, in general, does not repeat infor- mation contained in ASHRAE Handbooks and special publications. You cannot, therefore, rely on this manual as the only reference for design work. As you gain experience, make notes of important con- cepts and ideas (what worked and what did not work) and keep these notes in a readily accessible location. This manual is intended to point the way toward building such a design database. The best design reference available is the experience of your colleagues and peers. While an attempt has been made in this man- ual to incorporate the experience of design professionals, no static written material can replace dynamic face-to-face interaction with your colleagues. Use every opportunity to pick their brains, and let them tell you what did not work. Often, more is learned from fail- ures than from successes. 1.3 UNITS The first edition of this manual was written using I-P (inch- pound) units as the primary measurement system. In this edition SI (System International) units are shown in brackets following the I-P units. Conversions to SI units are “soft approximations” with, for example, 4 in. being converted as 100 mm (versus the more accu- 4⏐ INTRODUCTION rate conversion to 101.6 mm or use of a true SI commercial size increment for a given product). See the ASHRAE guide “SI for HVAC&R” (available at no cost from the ASHRAE Web site, www.ashrae.org) for detailed information on preferred measure- ment units and conversion factors for HVAC&R design work. 1.4 GENERAL BIBLIOGRAPHY In addition to specific references listed in each of the chapters of this manual, the following publications are generally useful to HVAC&R system designers.