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News>Issue Listing>July/August 2001 >Canadian Code—Grounding and Bonding CEC/NEC—How Different Are They?
Canadian Code
Grounding and Bonding CEC/NECHow Different Are They? |
In Canada, the Canadian Electrical Code and, in the United States, the National Electrical Code both deal extensively with grounding and bonding issues and for the same reasons—to minimize the possibilities of electrical fires and shocks. But in many instances, each code tackles the same issue in a different way, regarding use of terminology, materials and methods of installation.
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In Canada, the Canadian Electrical Code
and, in the United States, the National Electrical Code both
deal extensively with
grounding and bonding issues and for the same reasonsto
minimize the possibilities of electrical fires and shocks. But
in many instances, each code tackles the same issue in a
different way, regarding use of terminology, materials and
methods of installation.
This article discusses some of the differences between our
electrical codes, beginning with definitions of some of the
more frequently used grounding and bonding terms.
Terminology
A good place to start would be how we describe things. The CEC
and NEC often use different terminology. Differences in
terminology are no doubt among the more likely reasons for a
general lack of understanding of this subject.
The table below shows how the CEC and the NEC define some of our more familiar grounding and bonding terms.
Definition |
CEC |
NEC |
The conductor
connecting the
electrical system or
service equipment
to the grounding
electrode |
grounding conductor |
grounding electrode conductor |
The
conductor that interconnects electrical enclosures,
cable sheaths, raceways, etc. |
bonding
conductor |
equipment
grounding conductor |
The
grounded conductor (neutral) that serves as the current
return path for services, feeders and branch circuits |
identified
conductor |
grounded
conductor |
The
conductor used for bonding service cables, raceways,
etc. |
bonding conductor |
bonding
jumper |
A
grounding electrode made up of ground rods, grounding
plates, etc. |
artificial
grounding
electrode |
made
electrode |
Is it any wonder that people on both sides
of the border are confused by technical literature or when
reviewing drawings and specifications prepared using different
language?
The following tables show some differences
in the specified materials and how they are installed.
Grounding
Conductor (NECGrounding Electrode Conductor)
The Canadian Electrical Code and the National Electrical
Code provide different grounding conductor material
specifications. They also take a somewhat different approach
to determining the minimum wire sizes and ampacities.
The
CEC (Table 17) permits: |
The
NEC (Table 250-66) permits: |
Acceptable conductor materials - copper only
Minimum wire size - based on the ampacity of the
largest phase conductor |
Acceptable conductor materials - copper, aluminum or
copper clad aluminum
Minimum wire size - based on the cross-sectional area
of the largest phase conductor |
Grounding
Electrode
We also find some differences in what is considered an
acceptable grounding electrode. As mentioned earlier, what we
call an "artificial grounding electrode" in Canada
will be referred to as a "made electrode" in the
U.S. In Canada, the minimum length of a ground rod is three
metres (10 feet); in the U.S., the minimum length is 8 feet
(2.44 metres).
The following chart shows what each code
considers an acceptable grounding electrode on each side of
our border.
You will, no doubt, notice some major
differences in the code.
The
CEC permits: |
The
NEC permits: |
A metal underground water piping
system
A metal well casing
An artificial grounding
electrode consisting of either:
Concrete reinforcing rods
or bars
Ground rods
A plate electrode |
A
metal underground water piping system of metal well
casing with supplemental ground rods
An
effectively grounded metal frame of a building
Concrete
reinforcing rods or bars or a No. 4 cu 20 in. length
at the bottom of the footing
A
buried ground ring
A
made electrode
A rod or pipe electrode
A plate electrode |
The
CEC and NEC accept: |
The
CEC permits: |
The
NEC permits: |
Conductors -
copper or aluminum
(NEC also accepts copper-clad aluminum)
The sheaths of mineral-insulated and aluminum-
sheathed cables.
Bonding conductors in armoured cables |
Busbars or steel pipe
Rigid metal conduit except underground, where
subjected to corrosion or in concrete slab in contact
with the earth
Electrical metallic tubing except in corrosive areas,
where subjected to damage or in concrete slabs in
contact with the earth |
Rigid metal conduit
Intermediate
Electrical metallic
Flexible metal (liquid tight)
Cabletray
Cablebus framework |
Bonding
Conductor (NECEquipment Grounding Conductor)
The CEC and NEC provide some identical methods for
bonding electrical equipment, raceways, cable sheaths, etc.
But there are also some differences between the codes as shown
in the table directly above.
Hazardous
Locations
The electrical continuity of boxes, raceways and fittings must
be assured both within the hazardous locations and back to the
point of supply outside the hazardous location. This
requirement is included in both codes to minimize the
possibilities of arc or sparks that might ignite an explosive
or flammable atmosphere. The idea is the same in both codes,
but the codes specify an important difference.
Here is what each electrical code specifies
about hazardous locations.
Canadian Electrical Code Rule 10-614
In hazardous locations and in non-hazardous locations from
which hazardous locations are supplied, the electrical
continuity of metal raceways, boxes and the like, shall be
assured by one of the methods specified in Rule 10-606(1)(a),
(c) and (d).
This CEC rule prescribes that the enhanced
bonding methods used on the supply side of a main service
should be applied from the hazardous location equipment to the
last point of distribution (the panelboard) in the
non-hazardous location from which the equipment is supplied.
National Electric
Code Rule 501-16(a)
The locknut-bushing and double-locknut types of contacts
shall not be depended on for bonding purposes, but bonding
jumpers with proper fittings or other approved means of
bonding shall be used. Such means of bonding shall apply to
all intervening raceways, fittings, boxes, enclosures, etc.,
between the Class I locations and the point of grounding for
service equipment or point of grounding for a separately
derived system.
This NEC rule would imply that the
special bonding methods used on the supply side of a main
service should extend from the hazardous location equipment
back to the main service, or to the non-hazardous location
where the supply voltage is then transformed to a different
level.
Leslie Stoch, P.E. is principal of L. Stoch
& Associates, providing electrical engineering and ISO
9000 quality systems consulting. Prior to that, he spent over
20 years with Ontario Hydro as an electrical inspection
manager and engineer. Les holds a B.S. in electrical
engineering from Concordia University in Montreal.
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