General Requirements for Grounding and Bonding
Report on Proposals
for 2008 NEC
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The designations "National Electrical Code” and “NEC” refer to the
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Top 50 NEC Rules
General Requirements for Grounding and Bonding
By Mike Holt
You basically perform work on two types of systems --
solidly grounded or ungrounded. The general requirements for grounding
and bonding these systems can be summarized as follows.
Solidly grounded systems
You ground high-voltage system windings to the earth to help limit high
voltage imposed on the system windings from lightning, unintentional
contact with higher-voltage lines, or line surges. You must ground
parts of electrical equipment to the earth by electrically connecting
the building or structure disconnecting means [225.31 or 230.70] with a
grounding electrode conductor [250.64(A)] to a grounding electrode
[250.52, 250.24(A), and 250.32(A)].
Metal parts of the electrical installation are grounded to the earth
to reduce voltage imposed on them from lightning so as to prevent fires
from a surface arc within the building or structure. Grounding
electrical equipment to earth doesn't serve the purpose of providing a
low-impedance fault-current path to clear ground faults. In fact, the
Code prohibits the use of the earth as the effective ground-fault
current path [250.4(A)(5) and 250.4(B)(4)].
Grounding metal parts to earth is often necessary in areas where
discharge (arcing) of the voltage buildup (static) could cause
or undesirable conditions. Such an occurrence might be the failure of
electronic equipment being assembled on a production line, or a fire
explosion in a hazardous (classified) area. See 500.4 FPN 3. However,
grounding metal parts to earth doesn't protect electrical or electronic
equipment from lightning voltage transients (high-frequency voltage
impulses) on the circuit conductors. To protect electrical equipment
from high-voltage transients, you must install transient voltage
surge-protection devices in accordance with Article 280 at service
equipment and Article 285 at panelboards and other locations.
To remove dangerous voltage from ground faults, you must bond metal
parts of electrical raceways, cables, enclosures, and equipment to an
effective ground-fault current path with an equipment grounding
(bonding) conductor of a type specified in 250.118. The fault-current
path must have sufficiently low impedance to allow the fault current to
quickly rise to a level that will open the branch-circuit overcurrent
protection device. In addition, you must bond electrically conductive
metal water piping systems, metal sprinkler piping, metal gas piping,
and other metal-piping systems, as well as exposed structural steel
members that are likely to become energized, to an effective
ground-fault current path. A permanent, low-impedance fault-current
is one that facilitates the operation of the circuit overcurrent
The earth is not considered an effective ground-fault current path.
to read the rest of this article.
Power quality logging, electrical load studies and energy consumption
testing. The Fluke 1735 Power Logger is the ideal electrician or
technician's power meter for conducting energy studies and basic power
quality logging. Set the Power Logger up in seconds with the included
flexible current probes and color display. The power quality meter
measures most electrical power parameters, harmonics, and captures
voltage events. www.fluke.com/1735Codewatch
What's Wrong Here?
By Joe Tedesco
Think you know how this installation violates the
NEC? Visit EC&M's Web
site to see the answer.
Hint: Pay attention to the color red.
By Mike Holt
Q. I recently saw an advertisement for red
conduit that is to be used for emergency circuits. Is this a Code
Web site to see the answer.
By Steven Owen
Q. What is the maximum allowable ampacity of 12
AWG THHN insulated conductors installed in a strut-type channel raceway
that is 1 1/2 inches by 1 1/2 inches? There are a total 13 conductors
the raceway -- 12 of which are considered current carrying. The
terminals at the overcurrent protective devices for these conductors
rated at 75°C. It is unknown what the terminal ratings are at the
load end of the conductors. The actual loads supplied by these
conductors are not known.
Web site for the answer and explanation.
One touch automated design and one touch
automated protective device coordination options available in EasyPower
8.0 will be featured in the Hands-On training offered in Phoenix,
OCTOBER 30 - NOVEMBER 3! Learn how to streamline the implementation of
your Arc Flash and Electrical Safety Program. What used to take hours
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Code News Update
Report on Proposals for 2008
The Code is the definition of a "living document."
Constantly changing, it's the subject of thousands of proposals for
revision throughout each cycle. Earlier this year, the Code Making
Panels acted on 3,688 proposals associated with the 2008 NEC. Now the
deadline for comments is fast approaching.
If you're interested in submitting comments on any of the proposed
changes, you better get moving. All comments must be submitted to the
NFPA by 5 p.m. EST on October 20, 2006. You can submit your
comments online or download
a comment form.
Cool Electronic Cabinets
Prevent hot weather failures that can affect production. UL Listed
Cabinet Coolers from EXAIR produce 20 degree Fahrenheit air from an
ordinary supply of compressed air to cool electrical controls.
Thermostat control minimizes air usage. Maintains the NEMA 4, 4X
(stainless steel) and 12 rating of the enclosure. Web site offers
detailed information, downloadable drawings and PDF literature.
Shows and Events
The EC&M E-Tradeshow
will feature three FREE webinars on September 20.
Please e-mail your webinar attendance notice to John DeDad.
- "Ten Trends That Will Shape the Electrical Market," presented by
Lucy, chief editor of Electrical Wholesaling magazine. Learn the
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business and the bottom line.
- "Power Cable Basics," presented by John DeDad, senior director,
editorial and EC&M development. Learn why an MV power cable is a
complex and sophisticated product requiring careful testing and
handling. Find out how the current-carrying conductor, laminated
dielectric, MV insulation, semiconductive shield, metallic shield, and
outer jacket work together to control electrical stress and provide
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- "Hioki 3196 Quickstart Training," a hands-on webinar by PowerCET
will show you how to use the VIEW screen (waveform, vector and DMM
displays) to rapidly identify real-time power quality problems and the
AUTO SETUP for quick monitor installation. You'll also learn how to
create custom setups to capture more meaningful data, identify power
quality problems using the 3196's simultaneous capture of power quality
and energy data, and use Hioki PC-based software with a compact flash
card reader to transfer stored data and perform additional
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