Grounding and bonding in Canadian homes
"Grounding" and "bonding" are often used as if they mean the same thing. They are related but distinct, and understanding the difference makes the rest of residential wiring far easier to follow.
Grounding versus bonding
Bonding is the act of joining metal parts together so they share the same electrical potential. The metal box, the metal faceplate, the equipment grounding conductor, and the enclosure of an appliance are bonded so that none of them can sit at a different voltage than the others.
Grounding connects that bonded system to the earth through a grounding electrode, such as a driven rod or a connection to a metal water service. Bonding keeps everything in the home at the same potential; grounding ties that potential to the ground itself.
The grounding electrode
The grounding electrode is the physical connection to earth. In Canadian residential work this is commonly a ground rod, a connection to the metallic water service where permitted, or a concrete-encased electrode. The grounding electrode conductor runs from the electrode to the system at the main service.
- The connection must be mechanically secure and protected from corrosion.
- The conductor sizing follows the tables in the Canadian Electrical Code.
- Connections to a water pipe must account for the pipe being replaced later with non-metallic material.
What happens during a fault
Imagine a hot conductor inside an appliance works loose and touches the metal casing. If that casing is bonded back to the panel through an equipment grounding conductor, the fault current has a low-resistance path back to the source. That surge of current trips the breaker quickly, and the casing never becomes a shock hazard.
Bonding is what actually clears most faults. The earth connection alone is too high in resistance to trip a breaker. The low-resistance bonded path back to the panel is what does the work.
Common mistakes
| Mistake | Why it is a problem |
|---|---|
| Relying on a ground rod alone to clear faults | Earth resistance is far too high to trip a breaker reliably. |
| Connecting neutral and ground together downstream of the main | It puts normal load current on the grounding system, which should stay current-free. |
| Loose or painted-over bonding connections | Adds resistance and can interrupt the fault path when it is needed most. |
| Removing the bonding jumper on a metal box | Leaves the box and faceplate without a reliable return path. |
Where the code draws the line
Grounding and bonding requirements are set out in the Canadian Electrical Code, Part I. Service-level grounding work and panel changes are typically tasks that a province expects a licensed electrician to perform under permit. Replacing a single device is sometimes allowed for homeowners, but the rules vary by province, so check with your authority having jurisdiction first.
For how the panel and breakers fit into this picture, continue to breakers and panels. To see how fault detection is taken further, read about GFCI and AFCI protection.
Authoritative references
- CSA Group — Canadian Electrical Code, Part I (C22.1): csagroup.org
- Electrical Safety Authority (Ontario): esasafe.com
- Technical Safety BC: technicalsafetybc.ca