1. THE SUBJECT
G R O U N D I N G
AND THE
N E C

2. THE SPEAKER BOB LUDECKE Member IAEI CA Certified Electrician
Lic. Electrical Contractor
CSLB Industry Expert
CSLB Subject Matter Expert
Hands on Electrician Since 1974

3. SPECIAL THANKS TO
Thomas E. Trainor
Chief Electrical Inspector City of San Diego, California
Representing IAEI on CMP 7
Member - NFPA
Member - U.L. Electrical Council

4. ALSO GUILTY OF:
Member of the original NFPA Task Group on the Useability of the National Electrical Code
Chaired the sub-committee assigned to review Article 250 and make recommendations to improve it’s “useability”

5. The ‘99 NEC Completely Reorganized Exceptions Minimized
And Most Importantly
Performance Requirements Added

6. Prescriptive vs Performance
NEC rules are typically Prescriptive
A Prescriptive Rule tells you what to do
But, what it doesn’t tell you is.....
Why you’re doing it!

7. Prescriptive vs Performance
A Performance Rule is descriptive
It describes what has to be accomplished
And this description will most generally
Explain the intent of the rule

8. Why is this Important? Grounding continues to be a Mystery
Improper Grounding is Commonplace
Proper Grounding is vital for an installation
To protect from Fire and Electrocution

9. Why is this Important? It is my considered opinion,
That a better understanding of
The intent of the Grounding Rules
Will lead to better, safer installations

10. TYPICAL CIRCUIT OPERATION
Only four things can happen when a circuit is energized.
It can operate normally
There can be an overload
There can be a short circuit
There can be a ground fault

11. HOW DOES GROUNDING FIT IN?
As long as the circuit is operating normally,
GROUNDING IS NOT NEEDED

12. THE “UNGROUNDED” CIRCUIT
A circuit consisting of a transformer, A conductors and a light bulb will operate just fine (Check out the barn)
Grounding is not needed
To make it work
or To make it safe

13. HOW DOES GROUNDING FIT IN?
Under an overload condition,
GROUNDING IS NOT NEEDED
PROTECTION FROM OVERLOAD IS PROVIDED BY
THE OVERCURRENT DEVICE
Note that current is only flowing on the conductors that we installed to carry current

14. HOW DOES GROUNDING FIT IN?
Under a short circuit condition,
GROUNDING IS NOT NEEDED
PROTECTION AGAINST SHORT CIRCUIT IS PROVIDED BY
THE OVERCURRENT DEVICE
Again, current is only flowing on the conductors we installed to carry current

15. HOW DOES GROUNDING FIT IN?
Under a ground fault condition,
GROUNDING IS NOT NEEDED
PROTECTION AGAINST GROUND FAULT IS PROVIDED BY
THE OVERCURRENT DEVICE
HOWEVER……...

16. RETURN PATH REQUIRED
THE OVERCURRENT DEVICE CAN ONLY PROTECT AGAINST A GROUND FAULT IF,
THE CIRCUIT IS INSTALLED SO THAT ALL METAL PARTS ARE BONDED TOGETHER AND TO THE SERVICE NEUTRAL,
WHICH CREATES A LOW RESISTANCE PATH FOR FAULT CURRENT TO RETURN TO THE SOURCE OF SUPPLY

17. LETS LOOK AT A TYPICAL CIRCUITD
100’ of Overhead Distribution Line,
25’ of Service Drop,
25’ of Service Entrance Conductor,
100’ of Branch Circuit Conductors

18. LETS LOOK AT A TYPICAL CIRCUITD
Current flows…...

19. LETS LOOK AT A TYPICAL CIRCUITD
From the transformer to our Service

20. Through the Overcurrent Device to our Load
PATH OF CURRENT FLOW - NORMAL OPERATION L O A D
Through the Overcurrent Device to our Load

21. Through the Load returning to the Service
PATH OF CURRENT FLOW - NORMAL OPERATION L O A D
Through the Load returning to the Service

22. And back to the transformer
PATH OF CURRENT FLOW - NORMAL OPERATION L O A D
And back to the transformer

23. What determines the amount of current that will flow in this circuit?
PATH OF CURRENT FLOW - NORMAL OPERATION L O A D
What determines the amount of current that will flow in this circuit?

24. PATH OF CURRENT FLOW - NORMAL OPERATIOND
The Total RESISTANCE or IMPEDANCE in the circuit will determine the amount of current that will flow in the circuit

25. OHMS LAW WORKS E = I x R still works THINGS YOU CAN COUNT ON
We can change the code, or
Hire a different contractor, or
Use romex instead of EMT, but
E = I x R still works

26. How is our circuit protected against overload and short circuit?
OVERLOAD AND SHORT CIRCUIT CONDITIONS L O A D
How is our circuit protected against overload and short circuit?

27. THE OVERCURRENT DEVICE PROTECTS THIS CIRCUIT FROM BOTH
OVERLOAD AND SHORT CIRCUIT CONDITIONS
15A Circuit Breaker L O A D
THE OVERCURRENT DEVICE
PROTECTS THIS CIRCUIT FROM BOTH
OVERLOAD AND SHORT CIRCUIT

28. SUMMARIZING TO THIS POINT
CIRCUIT CONDITION
PROTECTION PROVIDED BY:
GROUNDING?
O/C PROT?
NORMAL OPERATION NO NO
OVERLOAD CONDITION NO
YES
SHORT CIRCUIT CONDITION
YES NO

29. GROUND FAULT CONDITION
So lets talk about a Ground Fault Condition
Which certainly sounds like the one condition where Grounding would be important and decide for ourselves whether
Grounding Provides Protection for Equipment or Personnel under a Ground Fault Condition

30. GROUND FAULT CONDITION
What happens if the hot conductor comes into contact with our metal box?

31. GROUND FAULT CONDITION
And our friend comes along and touches it?
IS HE IN JEOPARDY?

32. GROUND FAULT CONDITIONNO
NOT AT ALL
AND WHY NOT?

33. GROUND FAULT CONDITION
Because the transformer we’re looking at
IS NOT GROUNDED
so there is NO PATH THROUGH EARTH
for current to return to the transformer

34. GROUND FAULT CONDITION
Yes, that was a “Trick” question
Sorry about that
But the intent was to make a point

35. THINGS YOU CAN COUNT ON NO CIRCUIT - NO CURRENT
CURRENT DOES NOT FLOW UNLESS THERE IS A CONTINOUS PATH FROM ONE SIDE OF THE SOURCE OF SUPPLY TO THE OTHER
CURRENT CANNOT TRAVEL THROUGH THE EARTH TO RETURN TO A TRANSFORMER UNLESS THE TRANSFORMER IS GROUNDED

36. GROUND FAULT CONDITION
So our friend in this situation is perfectly safe
HOWEVER.....

37. GROUND FAULT CONDITION
What do we know about utility company transformers?

38. GROUND FAULT CONDITION
THEY’RE GROUNDED
And, with this transformer grounded, our friend is in serious jeopardy

39. SO WHY ARE THEY GROUNDED?
To minimize the damage caused if lightning strikes their distribution lines, or
If a 12 KV line drops onto a low voltage line,
In addition, grounding the neutral of the distribution system stabilizes the voltage.
So, basically for the same reason we ground services at buildings.

40. GROUND FAULT CONDITION
Because utility transformers are grounded, we need to do something to our equipment to keep our friend from being electrocuted

41. GROUND FAULT CONDITION
Can we protect our friend by grounding our metal equipment? Lets take a look.

42. GROUND FAULT CONDITION
Grounding our equipment provides a second path for fault current

43. GROUND FAULT CONDITION
The first is through our friend to earth and back to the transformer

44. GROUND FAULT CONDITION
The new second path is through our metal equipment to earth and back to the transformer

45. FAULT CURRENT PATH
We need to open a 15A Circuit Breaker as quickly as possible. This will require a fault current of 60A to 75A (4 to 5 times the rating of the breaker)
We can use Ohm’s Law to find out how much current will flow on our new path.

46. GROUND FAULT CONDITION
The voltage is 120V. We need to know the resistance in this circuit to calculate current

47. FAULT CURRENT PATH
Assuming a minimum of 5 ohms resistance through each grounding electrode, we know there is at least 10 ohms resistance in the fault path that we created by grounding our equipment.

48. FAULT CURRENT PATH THEREFORE, USING OHM’S LAW:
E = I x R and Transposing, I = E / R
I (current) = E(voltage) / R(resistance)
and so, I = 120 / 10 = 12A

49. ONLY 12 AMPS FAULT CURRENT PATH ABSOLUTELY NOT
WILL 12 AMPS TRIP OUR 15A CIRCUIT BREAKER?
ABSOLUTELY NOT

50. WITH EQUIPMENT GROUNDEDL O A D
So the Overcurrent Device does not open
And we have fried our friend

51. EQUIPMENT OR PERSONNEL
CONCLUSION
GROUNDING
DOES NOT PROTECT
EQUIPMENT OR PERSONNEL
FROM A GROUND FAULT

52. THE BONDING CONNECTIONL O A D
The vital connection left out of our discussion until now is the bonding of metal equipment to the service neutral

53. THE BONDING CONNECTION
Every piece of conductive metal which is a part of our system or likely to become energized
Must be connected together by an electrically continuous metal-to-metal contact or by an equipment grounding conductor

54. THE BONDING CONNECTION
These connections create an electrically continuous, low resistance path from every part of our system back to the service equipment
At the Service, these connections terminate on the Neutral Bus

55. THE BONDING CONNECTIONL O A D
These bonding connections let us use the neutral as a return path for fault current

56. THE BONDING CONNECTIONL O A D
Bonding provides a third path for fault current to return to the source of supply

57. FAULT CURRENT PATH
We need to open a 15A Circuit Breaker as quickly as possible. This will require a fault current of 60A to 75A (4 to 5 times the rating of the breaker)
We can use Ohm’s Law to find out how much current will flow on our new path.

58. FAULT CURRENT PATH The resistance in this path includes
100’ - #2 AL OH Distribution .032
25’ - #4 AL Service Drop .013
25’ - #2 CU Service Entrance .005
100’ - #14 CU Branch Circuit .307
Resistance to the point of fault .357 ohms

59. THE BONDING CONNECTION
.357 ohms L O A D
.3 ohms
The resistance from the point of fault
through our metal equipment back to the neutral
is assumed to be the same as the branch circuit wiring
and 100’ of #14 cu has a resistance of .3 ohm

60. THE BONDING CONNECTION
.357 ohms
.57 ohms L O A D
.3 ohms
The total resistance in this path created by bonding is .714 ohms

61. FAULT CURRENT PATH USING OHM’S LAW:
E = I x R and Transposing, I = E / R
I (current) = E(voltage) / R(resistance)
and so, I = 120 / .714 = 168A

62. THE BONDING CONNECTIONL O A D
The Fault Current Return Path through the Neutral allows 168A of fault current to flow and forces the overcurrent device to open

63. THE BONDING CONNECTIONL O A D
THIS PATH DOES NOT RELY ON
GROUNDING AND WORKS EVEN IF
OUR SYSTEM IS NOT GROUNDED

64. CONCLUSION
THE OVERCURRENT DEVICE PROTECTS AGAINST GROUND FAULT CONDITIONS PROVIDED THAT
OUR CIRCUITS HAVE BEEN INSTALLED SO THAT ALL CONDUCTIVE METALS ARE BONDED TOGETHER AND TO THE SERVICE NEUTRAL

65. GROUNDING IN REVIEW IS A CONNECTION TO EARTH INTENDED TO PROTECT OUR
ELECTRICAL SYSTEM FROM
LIGHTNING AND HIGH VOLTAGE

66. THE OVERCURRENT DEVICE
IN REVIEW
THE OVERCURRENT DEVICE
PROTECTS OUR ELECTRICAL SYSTEM
FROM OVERLOAD AND SHORT CIRCUIT

67. THE OVERCURRENT DEVICE
IN REVIEW
THE OVERCURRENT DEVICE
PROTECTS OUR ELECTRICAL SYSTEM
FROM A GROUND FAULT CONDITION
IF…….

68. PROPER BONDING HAS CREATED
IN REVIEW
PROPER BONDING HAS CREATED
AN ELECTRICALLY CONTINOUS,
LOW RESISTANCE PATH
FOR FAULT CURRENT TO RETURN
TO THE NEUTRAL AT THE SERVICE

69. “GROUNDING” SO WHAT’S THE PROBLEM? WHY DOES CONTINUE TO BE
A SUBJECT OF
MYSTERY AND CONFUSION?

70. IN MY OPINION
There are Three Areas where the CODE has not dealt well with this subject.
THEY ARE:
CONFUSING VOCABULARY
OVER-EMPHASIS ON GROUNDING
ACTUAL MISINFORMATION

71. VOCABULARY
WHICH TERMS ARE EASIER TO READ AND UNDERSTAND?
unGROUNDed
GROUNDed
GROUNDing
HOT
NEUTRAL
GROUND
ENOUGH SAID

72. OVER-EMPHASIS ON GROUNDING
ARTICLE 250 IN THE 1996 NEC IS DIVIDED INTO TWELVE PARTS
ELEVEN ARE ON GROUNDING
ONLY ONE IS ON BONDING
The Term “Low Impedance Ground Fault Return Path” is not mentioned at all

73. ACTUAL MISINFORMATION
IN THE 1990 NEC, THE FINE PRINT NOTES TOLD US THAT EQUIPMENT WAS GROUNDED IN ORDER TO
“FACILITATE THE OPERATION OF OVERCURRENT DEVICES UNDER FAULT CONDITIONS”

74. ACTUAL MISINFORMATION
IN THE 1996 NEC, SECTION STILL TELLS US THAT THE
“PATH TO GROUND” MUST BE OF LOW IMPEDANCE IN ORDER TO
“FACILITATE THE OPERATION OF THE CIRCUIT PROTECTIVE DEVICES”

75. A CONNECTION TO EARTH, and
ACTUAL MISINFORMATION
ARTICLE 100 PROVIDES GOOD DEFINITIONS OF:
GROUNDING, which is
A CONNECTION TO EARTH, and
BONDING, which is
AN INTERCONNECTION OF PARTS

76. THE CONNECTION TO EARTH, THE INTERCONNECTION OF PARTS
ACTUAL MISINFORMATION
BUT ARTICLE 250 HAS TENDED TO USE THE TERM “GROUNDING”
AS IF IT INCLUDED
THE CONNECTION TO EARTH,
THE INTERCONNECTION OF PARTS
and THE FAULT CURRENT PATH

77. A RESTRUCTURED AND REVISED ARTICLE 250
THE 1999 NEC BRINGS US…….
A RESTRUCTURED AND REVISED ARTICLE 250
Which not only:
Puts requirements in a more logical order,
And reduces the number of exceptions by changing them to positive text

78. THE 1999 NEC BRINGS US…….
BUT ALSO ADDS:
PERFORMANCE REQUIREMENTS FOR GROUNDING and BONDING,
AND THE NEW TERM
“FAULT CURRENT PATH”

79. THE 1999 NEC BRINGS US…….
AND, THROUGH THESE NEW PERFORMANCE REQUIREMENTS,
MORE CLEARLY IDENTIFIES WHAT GROUNDING, BONDING AND THE FAULT CURRENT PATH ARE REQUIRED TO ACCOMPLISH

80. THE 1999 NEC BRINGS US…….
Appendix E which provides cross references from the “96 to the ‘99 NEC and vice versa
Figure which graphically depicts the relationship of Bonding to the other Parts of Article 250 to emphasize it’s importance

82. HOWEVER
AMENDMENTS TO ARTICLE 250 IN THE 1999 NEC HAVE BEEN APPROVED BY CMP-5 AND AT THE NFPA ANNUAL MEETING IN ANAHEIM
WE CAN BENEFIT FROM THESE ADOPTED CHANGES WHICH WILL BE PUBLISHED IN THE 2002 NEC

83. Help From The 2002 NEC
In a new Section 250-2, the 2002 NEC adds definitions of technical terms, such as:
Ground Fault
Ground-Fault Current Path
Effective Ground-Fault Current Path
A real help in understanding the intent of the Grounding and Bonding requirements

84. Help From The 2002 NEC
Old Section becomes 250-4
Which now better explains the differences between Grounding and Bonding, and
Separates the requirements for Grounded and Ungrounded Systems
Another plus for user-friendly code

85. New Section 250-2 Definitions.
THE 2002 NEC
New Section Definitions.
Ground Fault.
An unintentional, electrically conducting connection between an ungrounded conductor of an electrical circuit and the normally non-current carrying conductors, metallic enclosures, metallic raceways, metallic equipment or earth.

86. New Section 250-2 Definitions.
THE 2002 NEC
New Section Definitions.
Ground-Fault Current Path.
An electrically conductive path from the point of a ground fault on a wiring system through normally non-current carrying conductors, equipment or the earth to the electrical supply source.

87. New Section 250-2 Definitions.
THE 2002 NEC
New Section Definitions.
FPN: Examples of ground-fault current paths could consist of any combination of equipment grounding conductors, metallic raceways, metallic cable sheaths, electrical equipment, and any other electrically conductive material such as metal water and gas piping, steel framing members, stucco mesh, metal ducting, reinforcing steel, shields of communication cables and the earth itself.

88. New Section 250-2 Definitions.
THE 2002 NEC
New Section Definitions.
Effective Ground-Fault Current Path.
An intentionally constructed, permanent, low impedance, electrically conductive path designed and intended to carry current under ground fault conditions from the point of a ground fault on a wiring system to the electrical supply source.

89. New Section 250-2 Definitions.
THE 2002 NEC
New Section Definitions.
FPN: An effective ground-fault current path is created by effectively bonding together all of the electrically conductive materials that are likely to be energized by the wiring system. Effective bonding is accomplished through the use of equipment grounding conductors, bonding jumpers or bonding conductors, approved metallic raceways, connectors and couplings, approved metallic sheathed cable and cable fittings, and other approved devices. A ground fault path is effective when it will safely carry the maximum ground fault current likely to be imposed on it.

90. New Section 250-2 Definitions.
THE 2002 NEC
New Section Definitions.
An effective ground-fault current path is created by effectively bonding together all of the electrically conductive materials that are likely to be energized by the wiring system.

91. New Section 250-2 Definitions.
THE 2002 NEC
New Section Definitions.
Effective bonding is accomplished through
the use of equipment grounding conductors, bonding jumpers or bonding conductors, approved metallic raceways, connectors and couplings, approved metallic sheathed cable and cable fittings, and other approved devices.

92. New Section 250-2 Definitions.
THE 2002 NEC
New Section Definitions.
A ground fault path is effective when it will safely carry the maximum ground fault current likely to be imposed on it.

93. Help From The 2002 NEC
Old Section becomes:
General Requirements for Grounding and Bonding
which is divided into:
(A) Grounded Systems, and
(B) Ungrounded Systems

94. Help From The 2002 NEC
New Section (A)
(1) Electrical System Grounding
(2) Grounding of Electrical Equipment
(3) Bonding of Electrical Equipment
(4) Bonding of Electrically Conductive Materials and Other Equipment
(5) Effective Ground Fault Current Path

95. Help From The 2002 NEC
New Section (A)
(1) Electrical System Grounding
Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher voltage lines and that will stabilize the voltage to earth during normal operation.

96. Help From The 2002 NEC
New Section (A)
(2) Grounding of Electrical Equipment
Non-current carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials.

97. Help From The 2002 NEC
New Section (A)
(3) Bonding of Electrical Equipment
Non-current carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the electrical supply source in a manner that establishes an effective ground fault current path.

98. Help From The 2002 NEC
New Section (A)
(4) Bonding of Electrical Conductive Materials and Other Equipment
Electrically conductive materials that are likely to become energized shall be connected together and to the electrical supply source in a manner that establishes an effective ground fault current path.

99. (5) Effective Ground Fault Current Path
Help From The 2002 NEC
New Section (A)
(5) Effective Ground Fault Current Path
Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a permanent, low impedance circuit capable of safely carrying the maximum ground fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source.
The earth shall not be used as the sole equipment grounding conductor or fault current path.

100. Help From The 2002 NEC
New Section (B)
(1) Grounding of Electrical Equipment
(2) Bonding of Electrical Equipment
(3) Bonding of Electrically Conductive Materials and Other Equipment
(4) Path for Fault Current

101. (1) Grounding of Electrical Equipment
Help From The 2002 NEC
New Section (B)
(1) Grounding of Electrical Equipment
Non-current carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage imposed by lightning, line surges, or unintentional contact with higher voltage lines and limit the voltage to ground on these materials

102. (2) Bonding of Electrical Equipment
Help From The 2002 NEC
New Section (B)
(2) Bonding of Electrical Equipment
Non-current carrying conductive materials enclosing electrical conductors or equipment, shall be connected together and to the supply system grounded equipment in a manner that creates a permanent, low impedance path for ground fault current which is capable of safely carrying the maximum fault current likely to be imposed on it.

103. (3) Bonding of Electrical Conductive Materials and Other Equipment
Help From The 2002 NEC
New Section (B)
(3) Bonding of Electrical Conductive Materials and Other Equipment
Electrically conductive materials that are likely to become energized shall be connected together and to the supply system grounded equipment in a manner that creates a permanent, low impedance path for ground fault current which is capable of safely carrying the maximum fault current likely to be imposed on it.

104. (4) Path for Fault Current
Help From The 2002 NEC
New Section (B)
(4) Path for Fault Current
Electrical equipment, wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a permanent, low impedance circuit from any point on the wiring system to the electrical supply source to facilitate the operation of overcurrent devices should a second fault occur on the wiring system.
The earth shall not be used as the sole equipment grounding conductor or fault current path.

105. IN CLOSING
THE CHANGES TO ARTICLE 250 IN THE ‘99 & ‘O2 NEC ARE EXTENSIVE
IT HAS BEEN COMPLETELY RENUMBERED AND REWORDED
MANY EXCEPTIONS HAVE BEEN REWRITTEN INTO POSITIVE TEXT

106. IN CLOSING
SOME RULES, SUCH AS , HAVE BEEN COMPLETELY CHANGED
OTHERS HAVE BEEN RELOCATED, REWRITTEN AND/OR REORGANIZED
THESE CHANGES WILL AFFECT EVERYONE INVOLVED IN THE ELECTRICAL INDUSTTRY

107. THE POSITIVE APPROACH
These changes are a blessing in disguise
We all need to get a fresh start on this subject and clarify our understanding of why we ground and bond electrical systems and how grounding and bonding are related to safe electrical installations

108. THE POSITIVE APPROACH
The best way to do that is to work through Article 250 as if it were totally new
Check that terms are used consistently as they are defined
Check the rules against what you see in the field

109. THE POSITIVE APPROACH
Always question the “why” of the rule
Don’t stop until you really understand it
And how to apply it on the job

110. THE POSITIVE APPROACH
And, when you review Grounding
Use the wording in the 2002 NEC
It’s the closest we’ve ever gotten to accurately describing this topic

111. THE POSITIVE APPROACH
Using the new wording in the 2002 NEC
Will make it easier to show contractors what Grounding and Bonding have to accomplish
And that’s important because

112. Ground-Fault Current Path
THE POSITIVE APPROACH
Grounding
Bonding
and the
Ground-Fault Current Path
are critical elements of electrical safety

113. FOR YOUR TIME AND ATTENTION
THANK YOU
FOR YOUR TIME AND ATTENTION