Bonding with Our Neighbors

Both the Canadian Electrical Code and its American counterpart, the National Electrical Code provide similar definitions for the metallic means of bonding electrical equipment and raceways. In this article, I’d like to review some of the similarities and differences in the acceptable bonding methods in Canada versus the United States. Let’s begin with the definition of bonding as expressed in our separate electrical codes.

According to the CE Code, bonding is “a low impedance path obtained by permanently joining all non-current-carrying metal parts to assure electrical continuity and having the capacity to conduct safely any current likely to be imposed on it.”

According to the NEC, bonding is “the permanent joining of metallic parts to form an electrically conductive path that ensures electrical continuity and the capacity to conduct safely any current likely to be imposed.”

As you can see, although some of our words are different and re-arranged in a different format, both definitions provide the same, understandable overall objectives. There is a greater difference in the words used in our separate electrical codes to describe bonding methods. Canada’s CE Code uses the term bonding conductor to define the methods we use for equipment bonding. The NEC term uses equipment grounding conductor. (This is sometimes a source of confusion when we use American literature. We really should get together on a common definition.)

But here is where our similarities come to an abrupt end. Both electrical codes have a common list of bonding methods recognized in both countries. But the NEC goes much further, offering a wider range of permissible options than our CE Code. I have italicized the bonding methods permitted by the NEC that are not used in Canada in the following bullets.

The Canadian Electrical Code permits the following materials to be used as bonding conductors:

  • Copper conductors or other corrosion-resistant material (usually aluminum)
  • Metal busbar or pipe
  • Rigid metal conduit (except stainless steel, directly buried, in concrete or masonry that is in contact with the earth or where corrosion or damage is probable)
  • Electrical metallic tubing (except in concrete or masonry in contact with the earth or where corrosion or damage is probable)
  • Copper or aluminum sheaths or the marked conductors of mineral-insulated cable (except that cables with aluminum sheaths require corrosion protection as necessary)
  • Sheaths of aluminum-sheathed cables (with corrosion protection as necessary)

The National Electrical Code permits a far broader range of materials that may be used as equipment grounding conductors, some with numerous conditions and therefore some of the methods of use appear to be fairly complex:

  • Copper, aluminum or copper-clad aluminum conductors
  • Rigid metal conduit
  • Intermediate metal conduit (a type of conduit not recognized by the CE Code)
  • Electrical metallic tubing
  • Flexible metal conduit when both conduit and fittings are listed for grounding (“listing” is the American equivalent of the CE Code term “approval”)
  • Flexible metal conduit unlisted for grounding (when used with listed fittings, maximum 20-amperes circuit overcurrent protection, up to 1.8 m in length and installed for purposes other than to provide flexibility)
  • Flexible metal tubing with fittings listed for grounding (circuit protection up to 20 amperes and up to 1.8 m in length)
  • Armour of armoured cables (when it is installed using methods so that it provides an effective fault path)
  • Copper sheaths of mineral-insulated cables
  • Type MC metal-clad cables where listed for grounding (using a combination of either bonding conductors and interlocked metal tape or bonding conductors and metallic sheaths)
  • Cable trays (when identified for grounding purposes, of suitable cross-sectional area and so marked, with properly selected connections or bonding jumpers and maintained by qualified personnel)
  • Cablebus framework (for branch circuits and feeders only)
  • Electrically-continuous metal raceways and auxiliary gutters listed for grounding

As you will notice, our Canadian Electrical Code is more prescriptive and permits only a narrower range of methods for bonding electrical equipment and raceways. The NEC is more objective based — it offers further ways of achieving the same result, but with lots of conditions. It also appears that the NEC provides more flexibility, but demands a more advanced level of knowledge when selecting and applying some of the available bonding options. Being more prescriptive, the CE Code is more rigid, offers fewer options, but more simple to interpret and apply. Which do you think is more practicable?

As with past articles, you should always consult with the local electrical inspection authority in each province or territory for a more authoritative interpretation of any of the above.

Leslie Stoch
Leslie Stoch, P. Eng, 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.