Devin Hanes
Member
- Location
- United States
I am seeking comment, guidance and correction on this Public Input that I am considering submitting next code cycle.
Public Input
1.) Section
250.4
2.) Revised Text
250.4 General Requirements for Grounding and Bonding. The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.
(A) Grounded Systems.
(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.
Informational Note No. 1: An important consideration for limiting the imposed voltage is the routing of bonding and grounding electrode conductors so that they are not any longer than necessary to complete the connection without disturbing the permanent parts of the installation and so that unnecessary bends and loops are avoided. Informational Note No. 2: See NFPA 780-2014, Standard for the Installation of Lightning Protection Systems, for information on
(2) Grounding of Electrical Equipment. Normally 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, unless specifically permitted elsewhere in this code.
(3) Bonding of Electrical Equipment. Normally 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, unless specifically permitted elsewhere in this code.
(4) Bonding of Electrically Conductive Materials and Other Equipment. Normally non–current-carrying 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, unless specifically permitted elsewhere in this code.
(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 low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be 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, unless specifically permitted elsewhere in this code.
(B) Ungrounded Systems.
(1) Grounding Electrical Equipment. Non–current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth in a manner that will limit the voltage imposed by lightning or unintentional contact with higher-voltage lines and limit the voltage to ground on these materials, unless specifically permitted elsewhere in this code.
Informational Note: See NFPA 780-2014, Standard for the Installation of Lightning Protection Systems, for information on installation of grounding and bonding for lightning protection systems.
(2) 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 supply system grounded equipment in a manner that creates a low-impedance path for ground-fault current that is capable of carrying the maximum fault current likely to be imposed on it, unless specifically permitted elsewhere in this code.
(3) Bonding of Electrically 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 low-impedance path for ground-fault current that is capable of carrying the maximum fault current likely to be imposed on it, unless specifically permitted elsewhere in this code.
(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 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 ground fault from a different phase occur on the wiring system, unless specifically permitted elsewhere in this code. The earth shall not be considered as an effective fault-current path .
3.) Proposed new wording
The only change is the addition of the phrase ", unless specifically permitted elsewhere in this code" in eight of the paragraphs in the section.
4.)Substantiation
4A.)The problem that is being resolved
Currently the existing language is a contradiction to later sections in the same article. Currently the language in this section strictly states all associated metal that is enclosing conductors or equipment must be grounded and bonded, later sections such as 250.80 exception, 250.86 exceptions 1, 2 and 3, 250.110 exceptions 1, 2 and 3, and 250.112(D), (F) and (I) contradict the strict statements of 250.4 and allow equipment to not be grounded or bonded.
4B.)How will this revision solve the problem
This revision will align the section with the rest of the article and eliminate the contradiction, adding to the usability and readability of the code.