CSA C22.2 No. 0.4-17: Bonding and Grounding Requirements for Electrical Equipment and Metal Parts

Scope and Applicability

CSA C22.2 No. 0.4-17, part of the Canadian Electrical Code (CE Code) Part II series, establishes the minimum requirements for the bonding and grounding of electrical equipment and exposed non-current-carrying metal parts that may become energized. The standard applies to equipment rated up to 750 V and is intended to ensure a safe path for fault current, limit touch voltages, and reduce the risk of electric shock and fire.

Key areas addressed include:

• General requirements for bonding conductors and connections
• Grounding electrode systems and connections
• Equipotential bonding in hazardous locations and around swimming pools
• Requirements for separately derived systems
• Provisions for maintenance and testing of grounding systems

Technical Requirements

Bonding Conductors and Connections

The standard specifies minimum sizing rules for bonding conductors based on the rating of the overcurrent device protecting the circuit. Bonding jumpers must be installed at service equipment, at the source of separately derived systems, and around conduits and other metal raceways that could interrupt the grounding path. All bonding connections must be mechanically secure and electrically continuous, using listed connectors or exothermic welding.

Grounding Electrode System

CSA C22.2 No. 0.4-17 defines requirements for grounding electrodes, including:

• Metal water pipe grounding (must be supplemented by at least one additional electrode)
• Concrete-encased electrodes (Ufer grounds)
• Ground rings and driven rods
• Plate electrodes

Resistance of a single electrode must not exceed 25 ohms; if higher, a second electrode must be added. The standard also permits the use of structural steel and continuous metal underground water pipe as electrodes under specific conditions.

Equipotential Bonding

In areas susceptible to voltage gradients (e.g., swimming pools, spas, and livestock facilities), the standard requires bonding all metal parts together to create an equipotential plane. Conductors must be sized at minimum 6 AWG copper (or equivalent) and must be connected to the grounding system.

Separately Derived Systems

Generators, transformers, and other separately derived systems must have a bonding jumper installed at only one location—either at the source or at the first disconnecting means—to prevent parallel neutral paths. The standard clarifies the methods for grounding these systems and the rules for connecting the grounded conductor to the grounding electrode at the source.

Implementation Highlights

Successful implementation of CSA C22.2 No. 0.4-17 requires careful coordination between design, installation, and inspection. Key considerations include:

• Continuity Testing — All bonding and grounding paths must be verified for low impedance using an ohmmeter or micro-ohmmeter before energization.
• Corrosion Protection — Connections buried in earth or exposed to corrosive environments must be protected by approved corrosion-resistant materials or coatings.
• Maintenance Provisions — Grounding electrodes and connections must be accessible for periodic inspection and testing. The standard recommends annual testing of ground resistance.

Compliance Notes

To demonstrate compliance with CSA C22.2 No. 0.4-17, manufacturers and installers should pay attention to the following:

1. Listed Equipment — All grounding and bonding devices must be listed or certified to the appropriate CSA product standards.
2. Labeling — Service equipment and separately derived systems must be permanently labeled with the type of grounding system and the location of the system bonding jumper.
3. Derating for Multiple Grounding Electrodes — When multiple electrodes are used, the resistance of the grounding electrode system is the parallel combination; the standard requires that the overall resistance be less than 25 ohms.
4. Hazardous Locations — Additional requirements from CSA C22.2 No. 0.4-17 and the CE Code Part I apply in Class I, II, and III hazardous locations. Bonding must be continuous and fault paths must have sufficiently low impedance to clear ground faults promptly.