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.
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.
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.
electrical system or
to the grounding
|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
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 (NEC—Grounding 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|
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
(NECalso 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)
• Cablebus framework
Bonding Conductor (NEC—Equipment 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.
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.