Electrical Grounding and Bonding

by Simmons, J. Philip

• ISBN13: 9781401859381
• ISBN10: 1401859380
• Edition: 1st
• Format: Paperback
• Copyright: 2004-12-28
• Publisher: CENGAGE Delmar Learning

Summary

Written in accordance with the 2005 National Electrical Code?, this new book provides readers with a comprehensive introduction to the essential elements of electrical grounding and bonding. It examines the critical concepts of calculating conductor sizes, reading and interpreting NEC? tables, the use of grounded conductor connections in DC and AC systems, as well as various installations and sizing. Material is reader-friendly and is accompanied by straightforward, easy-to-understand explanations of key concepts that foster understanding. A functional use of color and dynamic illustrations augments the book and further supports this thorough student- and professional-level approach to electrical grounding.

Table of Contents

Foreword	xiii
Preface	xv
Changes to Article 250 for the 2005 Edition of the NEC®	xix
Introduction	1	(1)
The Mystery	1	(1)
Definitions	2	(16)
Review of Ohm's Law and Basic Electrical Theory	18	(4)
Electric Shock Hazards	22	(3)
Review Questions	25	(2)
General	27	(22)
250.3 Application of Other Articles	27	(1)
250.4 General Requirements for Grounding and Bonding	27	(12)
250.4(A) Grounded Systems	28	(1)
250.4(A)(1) Electrical System Grounding	29	(1)
250.4(A)(2) Grounding of Electrical Equipment	30	(1)
250.4(A)(3) Bonding of Electrical Equipment	31	(1)
250.4(A)(4) Bonding of Electrically Conductive Materials and Other Equipment	32	(1)
250.5(A)(5) Effective Ground-Fault Current Path	33	(4)
250.4(B) Ungrounded Systems	37	(1)
250.4(B)(1) Grounding Electrical Equipment	38	(1)
250.4(B)(2) Bonding of Electrical Equipment	38	(1)
250.4(B)(3) Bonding of Electrically Conductive Materials and Other Equipment	39	(1)
250.4(B)(4) Path for Fault Current	39	(1)
250.6 Objectionable Current over Grounding Conductors	39	(4)
250.6(A) Arrangement to Prevent Objectionable Current	40	(1)
250.6(B) Alterations to Stop Objectionable Current	40	(2)
250.6(C) Temporary Currents Not Classified as Objectionable Currents	42	(1)
250.6(D) Limitations to Permissible Alterations	42	(1)
250.8 Connection of Grounding and Bonding Equipment	43	(2)
250.12 Clean Surfaces	45	(4)
Review Questions	46	(3)
System Grounding	49	(58)
250.20 Alternating-Current Circuits and Systems to Be Grounded	49	(6)
250.20(A) Alternating-Current Systems of Less than 50 Volts	50	(1)
250.20(B) Alternating-Current Systems of 50 Volts to 1000 Volts	51	(3)
250.20(D) Separately Derived Systems	54	(1)
250.20(E) Impedance Grounded Neutral Systems	54	(1)
250.21 Alternating-Current Systems of 50 Volts to 1000 Volts Not Required to Be Grounded	55	(3)
250.22 Circuits Not to Be Grounded	58	(1)
250.24 Grounding Service-Supplied Alternating-Current Systems	58	(15)
250.24(A) System Grounding Connections	58	(1)
250.24(A)(1) General	59	(1)
250.24(A)(2) Outdoor Transformer	60	(1)
250.24(A)(3) Dual-Fed Services	60	(1)
250.24(A)(4) Main Bonding Jumper As Wire or Busbar	61	(1)
250.24(A)(5) Load-Side Grounding Connections	62	(1)
250.24(B) Main Bonding Jumper	63	(1)
250.24(C) Grounded Conductor Brought to Service Equipment	64	(2)
250.24(C)(1) Routing and Sizing	66	(5)
250.24(C)(2) Parallel Conductors	71	(1)
250.24(D) Grounding Electrode Conductor	71	(1)
250.24(E) Ungrounded System Grounding Connections	72	(1)
250.26 Conductor to Be Grounded --- Alternating-Current Systems	73	(1)
250.28 Main Bonding Jumper and System Bonding Jumper	74	(3)
250.28(A) Material	74	(2)
250.28(B) Construction	76	(1)
250.28(C) Attachment	76	(1)
250.28(D) Size	76	(1)
250.30 Grounding Separately Derived Alternating-Current Systems	77	(16)
250.30(A) Grounded Systems	80	(1)
250.30(A)(1) System Bonding Jumper	80	(2)
250.30(A)(2) Equipment Bonding Jumper Size	82	(3)
250.30(A)(3) Grounding Electrode Conductor, Single Separately Derived System	85	(2)
250.250.30(A)(4) Grounding Electrode Conductor, Multiple Separately Derived Systems	87	(3)
250.30(A)(5) Installation	90	(1)
250.30(A)(6) Bonding	90	(1)
250.30(A)(7) Grounding Electrode	90	(1)
250.30(A)(8) Grounded Conductor	91	(1)
250.30(B) Ungrounded Systems	92	(1)
250.32 Buildings or Structures Supplied by Feeder(s) or Branch Circuit(s)	93	(4)
250.32(A) Grounding Electrode	93	(1)
250.32(B) Grounded Systems	94	(1)
250.32(B)(1) Equipment Grounding Conductor	94	(1)
250.32(B)(2) Grounded Conductor	95	(2)
250.32(C) Ungrounded Systems	97	(1)
250.32(E) Grounding Electrode Conductor	97	(1)
250.34 Portable and Vehicle-Mounted Generators	97	(3)
250.34(A) Portable Generators	97	(2)
250.34(B) Vehicle-Mounted Generators	99	(1)
250.34(C) Grounded Conductor Bonding	100	(1)
250.36 High-Impedance Grounded Neutral Systems	100	(7)
250.36(A) Grounding Impedance Location	101	(1)
250.36(B) Neutral Conductor	101	(1)
250.36(C) System Neutral Connection	102	(1)
250.36(D) Neutral Conductor Routing	102	(1)
250.36(E) Equipment Bonding Jumper	102	(1)
250.36(F) Grounding Electrode Conductor Location	103	(1)
250.36(G) Equipment Bonding Jumper Size	103	(1)
Review Questions	104	(3)
Grounding Electrode System and Grounding Electrode Conductor	107	(34)
250.50 Grounding Electrode System	107	(1)
250.52 Grounding Electrodes	108	(6)
250.52(A) Electrodes Permitted for Grounding	108	(1)
250.52(A)(1) Metal Underground Water Pipe	109	(1)
250.52(A)(2) Metal Frame of the Building or Structure	110	(1)
250.52(A)(3) Concrete-Encased Electrode	111	(1)
250.52(A)(4) Ground Ring	112	(1)
250.52(A)(5) Rod and Pipe Electrodes	112	(1)
250.52(A)(6) Plate Electrodes	113	(1)
250.52(A)(7) Other Local Metal Underground Systems or Structures	113	(1)
250.52(B) Electrodes Not Permitted for Grounding	113	(1)
250.53 Grounding Electrode System Installation	114	(6)
250.53(A) Rod, Pipe, and Plate Electrodes	114	(1)
250.53(B) Electrode Spacing	114	(1)
250.53(C) Bonding Jumper	115	(1)
250.53(D) Metal Underground Water Pipe	116	(1)
250.53(D)(1) Continuity	116	(1)
250.53(D)(2) Supplemental Electrode Required	117	(1)
250.53(F) Ground Ring	118	(1)
250.53(G) Rod and Pipe Electrodes	118	(1)
250.53(H) Plate Electrode	119	(1)
250.54 Supplementary Grounding Electrodes	120	(1)
250.56 Resistance of Rod, Pipe, and Plate Electrodes	120	(3)
250.58 Common Grounding Electrode	123	(1)
250.60 Use of Air Terminals	124	(1)
250.64 Grounding Electrode Conductor Installation	125	(8)
250.64(A) Aluminum or Copper-Clad Aluminum Conductors	125	(1)
250.64(B) Securing and Protection Against Physical Damage	125	(1)
250.64(C) Continuous	126	(1)
250.64(D) Grounding Electrode Conductor Taps	127	(4)
250.64(E) Enclosures for Grounding Electrode Conductors	131	(1)
250.64(F) To Electrode(s)	132	(1)
250.66 Size of Alternating-Current Grounding Electrode Conductor	133	(3)
250.66(A) Connections to Rod, Pipe, or Plate Electrodes	134	(1)
250.66(B) Connections to Concrete-Encased Electrodes	135	(1)
250.66(C) Connections to Ground Rings	135	(1)
250.68 Grounding Electrode Conductor and Bonding Jumper Connection to Grounding Electrodes	136	(1)
250.68(A) Accessibility	136	(1)
250.68(B) Effective Grounding Path	137	(1)
250.70 Methods of Grounding and Bonding Conductor Connection to Electrodes	137	(4)
Review Questions	138	(3)
Enclosure, Raceway, and Service Cable Grounding	141	(4)
250.80 Service Raceways and Enclosures	141	(1)
250.86 Other Conductor Enclosures and Raceways	142	(3)
Review Questions	144	(1)
Bonding	145	(28)
250.90 General	145	(1)
250.92 Services	146	(5)
250.92(A) Bonding of Services	146	(1)
250.92(B) Method of Bonding at the Service	147	(4)
250.94 Bonding for Other Systems	151	(1)
250.96 Bonding Other Enclosures	151	(2)
250.96(A) General	151	(1)
250.96(B) Isolated Grounding Circuits	152	(1)
250.97 Bonding for Over 250 Volts	153	(2)
250.98 Bonding Loosely Jointed Metal Raceways	155	(1)
250.100 Bonding in Hazardous (Classified) Locations	155	(2)
250.102 Equipment Bonding Jumpers	157	(4)
250.102(A) Material	157	(1)
250.102(B) Attachment	158	(1)
250.102(C) Size---Equipment Bonding Jumper on Supply Side of Service	158	(2)
250.102(D) Size---Equipment Bonding Jumper on Load Side of Service	160	(1)
250.102(E) Installation	160	(1)
250.104 Bonding of Piping Systems and Exposed Structural Steel	161	(6)
250.104(A) Metal Water Piping	161	(1)
250.104(A)(1) General	161	(1)
250.102(A)(2) Buildings of Multiple Occupancy	162	(1)
250.102(A)(3) Multiple Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s)	163	(1)
250.104(B) Other Metal Piping	164	(1)
250.104(C) Structural Metal	164	(1)
250.104(D) Separately Derived Systems	165	(1)
250.104(D)(1) Metal Water Piping System(s)	165	(1)
250.104(D)(2) Structural Metal	166	(1)
250.104(D)(3) Common Grounding Electrode Conductor	166	(1)
250.106 Lightning Protection Systems	167	(6)
Review Questions	168	(5)
Equipment Grounding and Equipment Grounding Conductors	173	(26)
250.110 Equipment Fastened in Place or Connected by Permanent Wiring Methods (Fixed)	173	(1)
250.112 Fastened in Place or Connected by Permanent Wiring Methods (Fixed)---Specific	174	(2)
250.118 Types of Equipment Grounding Conductors	176	(7)
250.119 Identification of Equipment Grounding Conductors	183	(1)
250.119(A) Conductors Larger Than 6 AWG	183	(1)
250.119(B) Multiconductor Cable	184	(1)
250.120 Equipment Grounding Conductor Installation	184	(1)
250.120(A) Raceway, Cable Trays, Cable Armor, Cablebus, or Cable Sheaths	184	(1)
250.120(B) Aluminum and Copper-Clad Aluminum Conductors	185	(1)
250.120(C) Equipment Grounding Conductors Smaller Than 6 AWG	185	(1)
250.122 Size of Equipment Grounding Conductors	185	(6)
250.122(A) General	185	(1)
250.122(B) Increased in Size	185	(1)
250.122(C) Multiple Circuits	186	(1)
250.122(D) Motor Circuits	186	(2)
250.122(F) Conductors in Parallel	188	(3)
250.122(G) Feeder Taps	191	(3)
250.124 Equipment Grounding Conductor Continuity	194	(1)
250.124(A) Separable Connections	194	(1)
250.126 Identification of Wiring Device Terminals	194	(5)
Review Questions	195	(4)
Methods of Equipment Grounding	199	(18)
250.130 Equipment Grounding Conductor Connections	199	(4)
250.130(A) For Grounded Systems	200	(1)
250.130(B) For Ungrounded Systems	200	(1)
250.130(C) Nongrounding Receptacle Replacement or Branch-Circuit Extensions	200	(3)
250.134 Equipment Fastened in Place or Connected by Permanent Wiring Methods (Fixed)---Grounding	203	(1)
250.134(A) Equipment Grounding Conductor Types	203	(1)
250.134(B) With Circuit Conductors	203	(1)
250.136 Equipment Considered Effectively Grounded	204	(1)
250.136(A) Equipment Secured to Grounded Metal Supports	204	(1)
250.140 Frames of Ranges and Clothes Dryers	204	(2)
250.142 Use of Grounded Circuit Conductor for Grounding Equipment	206	(1)
250.142(A) Supply-Side Equipment	206	(1)
250.142(B) Load-Side Equipment	206	(1)
250.146 Connecting Receptacle Grounding Terminal to Box	207	(4)
250.146(A) Surface-Mounted Box	208	(1)
250.146(B) Contact Devices or Yokes	209	(1)
250.146(C) Floor Boxes	209	(1)
250.146(D) Isolated Receptacles	209	(2)
250.148 Continuity and Attachment of Equipment Grounding Conductors to Boxes	211	(6)
250.148(A) Connections	212	(1)
250.148(B) Grounding Continuity	212	(1)
250.148(C) Metal Boxes	213	(1)
250.148(D) Nonmetallic Boxes	213	(1)
250.148(E) Solder	214	(1)
Review Questions	214	(3)
Appendix A Some Fundamentals of Equipment-Grounding Circuit Design	217	(10)
Appendix B Investigation and Testing of Footing-Type Grounding Electrodes for Electrical Installations	227	(10)
Appendix C Understanding Ground Resistance Testing	237	(40)
Appendix D Report of Research on Conduit Fitting Ground-Fault Current Withstand Capability	277	(10)
Index	287