2008 NEC® Changes: Chapter 2 (Part 3)
NEC Digest®, February 2007 (necdigest®, National Electrical Code®, and NEC® are registered trademarks of the National Fire Protection Association, Inc., Quincy, MA 02169)
By James Stallcup, Sr. and Mark Ode
Editor's Note: James Stallcup Sr. and Mark Ode, two of the most knowledgeable and well-respected experts in the electrical industry, have teamed up to write a series of special Code Issues articles giving us the scoop on the most important upcoming changes for NEC 2008.
2008 NEC Products
In the third of a series discussing proposed changes to the 2008 National Electrical Code® (NEC®), the authors cover more important changes to Chapter 2. To help simplify and clarify each change, words that have been deleted are shown with a strike through and words that have been added are underlined.
2005 NEC
225.18 Clearance from Ground.
Overhead spans of open conductors and open multiconductor cables of not over 600 volts, nominal, shall have a clearance of not less than the following: [Remainder unchanged].
2008 NEC
225.18 Clearance for Overhead Conductors and Cables.>
Overhead spans of open conductors and open multiconductor cables of not over 600 volts, nominal, shall have a clearance of not less than the following: [Remainder unchanged].
Author’s Comment: The term “grade” was too subjective, as suggested in the proposal, since there is initial grade at time of construction, there is intermediate grade during construction, and then final grade at the end of construction. “Grade” could ultimately be changed at any future time. The title change uses the actual text within the section itself.
2005 NEC
225.39 Rating of Disconnect.
The feeder or branch-circuit disconnecting means shall have a rating of not less than the load to be supplied, determined in accordance with Parts I and II of Article 220 for branch circuits, Parts III or IV of Article 220 for feeders, or Part V of Article 220 for farm loads. In no case shall the rating be lower than specified in 225.39(A), (B), (C), or (D).
2008 NEC
225.39 Rating of Disconnect.
The feeder or branch-circuit disconnecting means shall have a rating of not less than the load to be supplied, determined in accordance with Parts I and II of Article 220 for branch circuits, Parts III or IV of Article 220 for feeders, or Part V of Article 220 for farm loads. Where the branch circuit or feeder disconnecting means consists of more than one switch or circuit breaker, as permitted by 225.33, combining the ratings of all the switches or circuit breakers for determining the rating of the disconnecting means shall be permitted. In no case shall the rating be lower than specified in 225.39(A), (B), (C), or (D).
Author’s Comment: Since a disconnect is a device or group of devices, permission is inherent to add each device to reach a total rating in compliance with this section. The new revised text will eliminate any confusion that there is inherent permission for breakers to be additive in calculating the rating of a disconnect means.
2005 NEC
230.24 Clearances.
(B) Vertical Clearance from Ground.
Service-drop conductors, where not in excess of 600 volts, nominal, shall have the following minimum clearance from final grade:
(1) 3.0 m (10 ft) – at the electric service entrance to buildings, also at the lowest point of the drip loop of the building electric entrance, and above areas or sidewalks accessible only to pedestrians, measured from final grade or other accessible surface only for service-drop cables supported on and cabled together with a grounded bare messenger where the voltage does not exceed 150 volts to ground
(2) 3.7 m (12 ft) – over residential property and driveways, and those commercial areas not subject to truck traffic where the voltage does not exceed 300 volts to ground
(3) 4.5 m (15 ft) – for those areas listed in the 3.7-m (12 ft) classification where the voltage exceeds 300 volts to ground
(4) 5.5 m (18 ft) – over public streets, alleys, roads, parking areas subject to truck traffic, driveways on other than residential property, and other land such as cultivated, grazing, forest, and orchard
2008 NEC
230.24 Clearances.
(B) Vertical Clearance for Service-drop Conductors.
Service-drop conductors, where not in excess of 600 volts, nominal, shall have the following minimum clearance from final grade:
(1) 3.0 m (10 ft) – at the electric service entrance to buildings, also at the lowest point of the drip loop of the building electric entrance, and above areas or sidewalks accessible only to pedestrians, measured from final grade or other accessible surface only for service-drop cables supported on and cabled together with a grounded bare messenger where the voltage does not exceed 150 volts to ground
(2) 3.7 m (12 ft) – over residential property and driveways, and those commercial areas not subject to truck traffic where the voltage does not exceed 300 volts to ground
(3) 4.5 m (15 ft) – for those areas listed in the 3.7-m (12 ft) classification where the voltage exceeds 300 volts to ground
(4) 5.5 m (18 ft) – over public streets, alleys, roads, parking areas subject to truck traffic, driveways on other than residential property, and other land such as cultivated, grazing, forest, and orchard
Author’s Comment: The term “grade” was not specific enough, as proposed, since there is initial grade at time of construction, there is intermediate grade during construction, and then final grade at the end of construction. “Grade” could ultimately be changed at any future time. The title change uses the actual text within the section itself.
2005 NEC
230.44 Cable Trays.
Cable tray systems shall be permitted to support service-entrance conductors. Cable trays used to support service-entrance conductors shall contain only service-entrance conductors..
Exception: Conductors, other than service-entrance conductors, shall be permitted to be installed in a cable tray with service-entrance conductors, provided a solid fixed barrier of a material compatible with the cable tray is installed to separate the service-entrance conductors from other conductors installed in the cable tray.
2008 NEC
230.44 Cable Trays.
Cable tray systems shall be permitted to support service-entrance conductors. Cable trays used to support service-entrance conductors shall contain only service-entrance conductors.
Exception: Conductors, other than service-entrance conductors, shall be permitted to be installed in a cable tray with service-entrance conductors, provided a solid fixed barrier of a material compatible with the cable tray is installed to separate the service-entrance conductors from other conductors installed in the cable tray. Cable trays shall be identified with permanently affixed labels with the wording “Service-Entrance Conductors.” The labels shall be located so as to be visible after installation and placed so that the service-entrance conductors may be readily traced through the entire length of the cable tray.
Author’s Comment: Text has been added to the exception for conductors, other than service entrance conductors, to be installed in cable trays with service entrance conductors. Where these other conductors are added, they must be separated by a fixed solid barrier but, now, in addition, labels must be installed so as to be readily visible after installation and placed so the service entrance conductors can be readily traced through the entire length to the cable tray.
2005 NEC
230.71 Maximum Number of Disconnects.
(A) General. The service disconnecting means for each service permitted by 230.2, or for each set of service-entrance conductors permitted by 230.40, Exception Nos. 1, 3, 4, or 5, shall consist of not more than six switches or sets of circuit breakers, or a combination of not more than six switches and sets of circuit breakers, mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard. There shall be not more than six sets of disconnects per service grouped in any one location. For the purpose of this section, disconnecting means used solely for power monitoring equipment, transient voltage surge suppressors, or the control circuit of the ground-fault protection system or power-operable service disconnecting means, installed as part of the listed equipment, shall not be considered a service disconnecting means.
230.82 Equipment Connected to the Supply Side of Service Disconnect.
Only the following equipment shall be permitted to be connected to the supply side of the service disconnecting means:
(4) Instrument transformers (current and voltage), impedance shunts, load management devices, and arresters
(8) Ground-fault protection systems or transient voltage surge suppressors, where installed as part of listed equipment, if suitable overcurrent protection and disconnecting means are provided
230.94 Relative Location of Overcurrent Device and Other Service Equipment.
The overcurrent device shall protect all circuits and devices.
Exception No. 2: High-impedance shunt circuits, surge arresters, surge-protective capacitors, and instrument transformers (current and voltage) shall be permitted to be connected and installed on the supply side of the service disconnecting means as permitted in 230.82.
2008 NEC
230.71 Maximum Number of Disconnects.
(A) General. The service disconnecting means for each service permitted by 230.2, or for each set of service-entrance conductors permitted by 230.40, Exception Nos. 1, 3, 4, or 5, shall consist of not more than six switches or sets of circuit breakers, or a combination of not more than six switches and sets of circuit breakers, mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard. There shall be not more than six sets of disconnects per service grouped in any one location. For the purpose of this section, disconnecting means used solely for power monitoring equipment, surge protective devices, or the control circuit of the ground-fault protection system or power-operable service disconnecting means, installed as part of the listed equipment, shall not be considered a service disconnecting means.
230.82 Equipment Connected to the Supply Side of Service Disconnect.
Only the following equipment shall be permitted to be connected to the supply side of the service disconnecting means:
(4) Instrument transformers (current and voltage), impedance shunts, load management devices, surge arresters and Type 1 surge protective devices
(8) Ground-fault protection systems or Type 2 surge protective devices, where installed as part of listed equipment, if suitable overcurrent protection and disconnecting means are provided
230.94 Relative Location of Overcurrent Device and Other Service Equipment.
The overcurrent device shall protect all circuits and devices.
Exception No. 2: High-impedance shunt circuits, surge arresters, Type 1 surge protective devices, surge-protective capacitors, and instrument transformers (current and voltage) shall be permitted to be connected and installed on the supply side of the service disconnecting means as permitted in 230.82.
Author’s Comment: Underwriters Laboratories is combining the categories of Surge Arresters (Article 280) and Transient Voltage Surge Suppressors (Article 285) into one category and Standard, UL 1449, renamed Surge Protective Devices (SPDs). UL 1449 will include SPD designations Type 1 and Type 2 for permanently connected devices for use on circuits not exceeding 600 V. The technology of both low voltage Surge Arresters and TVSSs is now basically the same, thereby justifying coverage under one Standard, UL 1449, and one test program with consideration given to the installation location on the line side (Type 1) or load side (Type 2) of the service disconnect overcurrent protection. The Surge Arrester designation will only be retained for devices used in circuits of 1 kV and over and evaluated to IEEE C62.11-1999.
2005 NEC
230.205 Disconnecting Means.
(A) Location. The service disconnecting means shall be located in accordance with 230.70.
2008 NEC
230.205 Disconnecting Means.
(A) Location. The service disconnecting means shall be located in accordance with 230.70.
For either overhead or underground primary distribution systems on private property, the service disconnect shall be permitted to be located in a location that is not readily accessible.
Author’s Comment : There are many installations where the service point is at the edge of the property and a high voltage switch is the actual service disconnect for the distribution system, which then becomes a feeder for multiple buildings on the property; the disconnect requirements in 225 would apply to the buildings.
2005 NEC
240.4 Protection of Conductors.
(D) Small Conductors. Unless specifically permitted in 240.4(E) or (G), the overcurrent protection shall not exceed 15 amperes for 14 AWG, 20 amperes for 12 AWG, and 30 amperes for 10 AWG copper; or 15 amperes for 12 AWG, and 25 amperes for 10 AWG aluminum and copper-clad aluminum after any correction factors for ambient temperature and number of conductors have been applied.
2008 NEC
240.4 Protection of Conductors.
(D) Small Conductors. Unless specifically permitted in 240.4(E) or (G), the overcurrent protection shall not exceed the following after any correction factors for ambient temperature and number of conductors have been applied.
(1) 18 AWG Copper. 7 amperes for 18 AWG copper provided all the following conditions are met:
- Continuous loads do not exceed 5.6 amperes
- Overcurrent protection is provided by one of the following:
- Branch-circuit rated circuit breakers listed and marked for use with 18 copper AWG wire
- Branch-circuit rated fuses listed and marked for use with 18 AWG wire
- Class CC, Class J, or Class T fuses
(2) 16 AWG Copper. 10 amperes for 16 AWG copper provided all the following conditions are met:
- Continuous loads do not exceed 8 amperes
- Overcurrent protection is provided by one of the following:
- Branch-circuit rated circuit breakers listed and marked for use with 16 copper AWG wire
- Branch-circuit rated fuses listed and marked for use with 16 AWG wire
- Class CC, Class J, or Class T fuses
(3) 14 AWG Copper or 12 AWG Aluminum. 15 amperes for 14 AWG copper or 12 AWG aluminum and copper-clad aluminum.
(4) 12 AWG Copper. 20 amperes for 12 AWG copper.
(5) 10 AWG Aluminum and Copper-clad Aluminum. 25 amperes for 10 AWG aluminum and copper-clad aluminum.
(6) 10 AWG copper. 30 amperes for 10 AWG copper.
Author’s Comment: Small conductors in 18 AWG and 16 AWG sizes were added to correspond to the permission to use these smaller conductors based on NFPA 79, UL 508, UL 508A, and various small conductors specified and permitted in Article 400 for flexible cords and cables, as well as control circuits in Articles 725, 760, and communications circuits in Chapter 8.
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Reprinted with permission from necdigest®, Copyright 2007, National Fire Protection Association, Quincy, MA 02169
necdigest®, National Electrical Code®, and NEC® are registered trademarks of the National Fire Protection Association, Inc., Quincy, MA 02169
