Evaluation of Electrical Feeder and Branch Circuit Loading: Phase I FINAL REPORT BY: Tammy Gammon, Ph.D., P.E. Georgia USA January 2017 © 2017 Fire Protection Research Foundation 1 Batterymarch Park, Quincy, MA 02169-7417, USA Email: [email protected] Web: nfpa.org/foundation This page intentionally blank —— Page ii —— FOREWORD Interest has been growing in recent years to investigate and clarify the degree to which the feeder and branch circuit load design requirements in NFPA 70, National Electrical Code® (NEC®) need to be adjusted based on the increasing pace of technological innovation along the entire span of the electrical power chain. There are multiple factors driving this issue and supporting the need to address this topic. For example, today’s Energy Codes are driving down the electrical load presented by end use equipment and thus load growth assumptions that justify “spare capacity” should be re-examined. In addition, larger than necessary transformers that supply power to feeder and branch circuits expose unnecessary flash hazard to electricians working on live equipment. This report summarizes a Phase I effort to develop a data collection plan to provide statistically significant load data for a variety of occupancy and loading types to provide a technical basis for considering revisions to the feeder and branch circuit design requirements in the National Electrical Code®. This initial effort has an emphasis on general commercial (office) occupancies, and the deliverables provide a review of the literature, and clarify the key elements of a data collection plan in support of a potential second phase (not included in the scope of this effort). —— Page iii —— This page intentionally blank —— Page iv —— ACKNOWLEDGEMENTS The Fire Protection Research Foundation expresses gratitude to the report author Tammy Gammon, Ph.D., P.E. located in Georgia USA. The Research Foundation appreciates the guidance provided by the Project Technical Panelists, the funding provided by the project sponsors, and all others that contributed to this research effort. Special thanks are expressed to the following Panel members: Robert Arno, Harris Corp. & IEEE Fellow; Mark Earley, NFPA; Mark Hilbert, IAEI & CMP-2 Chair; Brian Liebel, Illuminating Engineering Society of North America; and Mark Lien, Illuminating Engineering Society of N.A. (Alt to B Liebel). Thanks are also extended to the following Sponsors: Michael Berthelsen, University of Minnesota; Brett Garrett, The Ohio State University (alternate for Bob Wajnryb); Lou Galante, University of Iowa; Jeff Gambrall, University of Iowa (Alternate to Lou Galante); Dean Hansen, University of Texas Austin; Kane Howard, Michigan State University; Michael Hughes, Michigan Association of Physical Plant Administrators; Jim Jackson, University of Nebraska (alternate for Brian Meyers); Paul Kempf, University of Notre Dame; Brian Meyers, University of Nebraska; Bob Wajnryb, The Ohio State University; and Bob Yanniello, Eaton Corporation. Gratitude is likewise expressed to three liaisons that supported this effort: Mike Anthony, University of Michigan; Jim Harvey, University of Michigan; and Richard Robben, Ann Arbor, MI. The content, opinions and conclusions contained in this report are solely those of the authors and do not necessarily represent the views of the Fire Protection Research Foundation, NFPA, Technical Panel or Sponsors. The Foundation makes no guaranty or warranty as to the accuracy or completeness of any information published herein. About the Fire Protection Research Foundation The Fire Protection Research Foundation plans, manages, and communicates research on a broad range of fire safety issues in collaboration with scientists and laboratories around the world. The Foundation is an affiliate of NFPA. About the National Fire Protection Association (NFPA) Founded in 1896, NFPA is a global, nonprofit organization devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards. The association delivers information and knowledge through more than 300 consensus codes and standards, research, training, education, outreach and advocacy; and by partnering with others who share an interest in furthering the NFPA mission. All NFPA codes and standards can be viewed online for free. NFPA's membership totals more than 60,000 individuals around the world. —— Page v —— Keywords: electrical feeder, branch circuit, loading, transformer, NEC, National Electrical Code, NFPA 70 Report number: FRPF-2 —— Page vi —— PROJECT TECHNICAL PANEL Robert Arno, Harris Corp. & IEEE Fellow (NY) Mark Earley, NFPA (MA) Mark Hilbert, IAEI & CMP-2 Chair (NH) Brian Liebel, Illuminating Engineering Society of North America (NY) Mark Lien, Illuminating Engineering Society of N.A. (NY) (Alt to B Liebel) PROJECT SPONSORS Eaton Corporation, Bob Yanniello Michigan Association of Physical Plant Administrators, Michael Hughes Michigan State University, Kane Howard The Ohio State University, Bob Wajnryb and Brett Garrett (alternate) University of Iowa, Lou Galante and Jeff Gambrall (alternate) University of Minnesota, Michael Berthelsen University of Nebraska, Brian Meyers and Jim Jackson (alternate) University of Notre Dame, Paul Kempf University of Texas Austin, Dean Hansen PROJECT LIAISONS Mike Anthony, University of Michigan (MI) Jim Harvey, University of Michigan (MI) Richard Robben, Ann Arbor, MI —— Page vii —— This page intentionally blank —— Page viii —— Fire Protection Research Foundation Project Review of Literature and Data Collection Plan Evaluation of Electrical Feeder and Branch Circuit Loading: Phase 1 Submitted by Tammy Gammon, Ph.D., P.E. January 2017 Project Technical Panel Mark Hilbert, IAEI and NEC Code-Making Panel 2 Chair Robert Arno, Harris Corporation Mark Earley, NFPA Brian Liebel, IES Project Sponsors University of Minnesota The Ohio State University University of Iowa University of Texas – Austin Michigan State University Michigan Association of Physical Plant Administrators University of Nebraska University of Notre Dame Eaton Corporation EXECUTIVE SUMMARY The purpose of this Phase I project is to conduct a literature review and to develop a data collection plan for an ambitious Phase II study on the evaluation of electrical feeder and branch circuit loading. The intent of this research is to evaluate electrical feeder and branch circuit loading given present National Electrical Code requirements, electrical safety, energy conservation, and reduction of capital investment. This research project focuses on commercial buildings. Report Sections 1 through 7 cover a review of related work and published data. Specifically, electricity usage and commercial building demographics are reviewed in Sections 1 and 2 to provide insight into the number of feeders and branch circuits installed in the United States and the amount of electricity supplied by them. Furthermore, Section 2 on commercial buildings and Section 3 on end-use loads have been included because the characteristics of the commercial buildings determine the electrical loads and the design of the electrical feeders and branch circuits supplying those loads. Section 4 addresses some of the factors which shape end-use equipment decisions and includes energy consumption projections for commercial buildings to the year 2040. Commercial building energy conservation codes are covered in Section 5 with a focus on lighting and power requirements in ASHRAE 90.1. In Section 6, the following engineering practices are discussed: one utility, traditional building electrical system design, and design in federal buildings. The NEC’s minimum lighting power requirements are also compared with ASRHAE 90.1 and other guidelines in Section 6. Section 7 addresses transformer efficiency and electrical safety issues as a function of transformer loading. Section 7 contains the author’s analysis regarding concern that lightly loaded transformers (supplying lightly loaded feeders) are associated with additional energy losses and increased arc flash hazards. The data collection plan is presented in Section 8. Although included as the final section of this report, Section 8 has been written to serve as a document which can stand alone, independent of the other report sections. ii TABLE OF CONTENTS 1 Electricity Usage in the United States ................................................................................. 1 1.1 Electric Utility Customers and Consumption................................................................. 1 1.2 Seasonal Influences and Climate ................................................................................. 2 2 Commercial Buildings ......................................................................................................... 5 2.1 General Demographics for All Commercial Buildings [5] .............................................. 5 2.2 Commercial Building Types and Specific Demographics [5] ......................................... 8 2.3 Commercial Building Energy Usage by Geography [5] ................................................11 2.4 Commercial Building Energy Usage by Building Type [5] ............................................15 2.5 Electric Utility Commercial Building Loading ...............................................................18 3 Building End-Use Loads and Electricity Consumption ........................................................19 3.1 End-Use Load Types and CBECS Models [5] .............................................................19 3.2 CBECS