Definitions and general rules

The code is a legal document, and like any legal document it depends on precise words. "Bonding" and "grounding" mean different things; a "feeder" is not a "branch circuit"; "readily accessible" is a stricter requirement than "accessible". Many disagreements with inspectors, and many wrong answers on exams, come from reading a word in its everyday sense instead of its code definition. This chapter covers the definitions every electrician needs, then the general rules that apply to every installation: approval and marking, workmanship and connections, identification of conductors, locations and enclosures, and working space.

Where the definitions are

In the CEC, definitions are in Section 0. A defined term has the meaning given there everywhere in the code, unless a particular section defines it differently for its own purposes (for example, Section 18 defines terms used for hazardous locations). When a rule seems ambiguous, the first step is to check whether its key words are defined.

Essential definitions

Circuits: service, feeder and branch circuit

• Consumer's service (often just "service"): the conductors and equipment from the supply authority's point of connection to the service box or equivalent, which controls and protects the whole installation.
• Feeder: the conductors between the service equipment (or another source, such as a transformer or generator) and the final branch-circuit overcurrent device. A feeder from the main panel to a subpanel is the common example.
• Branch circuit: the conductors between the final overcurrent device and the outlets it supplies. A 15 A receptacle circuit in a bedroom is a branch circuit.

Different rules apply to each, so identifying which one you are working on is the first step in sizing conductors and protection.

Grounding and bonding

• Grounding: a permanent and continuous conductive path to the earth with sufficient ampacity to carry any fault current liable to be imposed on it. The grounding conductor connects the system (or equipment) to the grounding electrode.
• Bonding: a low-impedance path obtained by permanently joining all non-current-carrying metal parts to ensure electrical continuity and having the capacity to conduct safely any current likely to be imposed. The bonding conductor connects metal enclosures, raceways and equipment back to the service or system grounding point.
• Identified conductor: the conductor intentionally connected to ground in a grounded system, usually the neutral. It is identified by white or grey insulation and is a current-carrying conductor, not a bonding conductor.

The distinction matters on every job. The neutral carries normal load current back to the source. The bonding or equipment grounding conductor carries current only during a fault, to trip the breaker. Connecting them together anywhere other than the service (or a separately derived source) puts normal current on metal parts, a common and dangerous error (Lesson 9).

Load and location terms

• Continuous load: a load where the maximum current is expected to continue for three hours or more. Water heaters, space heating, many lighting loads and most commercial loads are continuous.
• Ampacity: the current a conductor can carry continuously under its conditions of use without exceeding its temperature rating (Lesson 4).
• Dwelling unit: one or more rooms used as a housekeeping unit by one or more persons, with space for eating, living and sleeping, and permanent provisions for cooking and sanitation.
• Dry, damp and wet locations: a dry location is not normally subject to moisture; a damp location is partly protected but subject to moderate moisture (such as a covered porch or some basements); a wet location is exposed to weather, water or saturation (outdoors exposed, underground, in concrete in contact with earth). Wiring methods and equipment must suit the location.
• Readily accessible: capable of being reached quickly for operation, renewal or inspection, without climbing over obstacles or using a portable ladder. "Accessible" alone is less demanding: it may require removing a cover.
• Live (energized): electrically connected to a source of voltage difference, or electrically charged so as to have a potential different from ground.

General rules for every installation

Approval, marking and instructions

Equipment must be approved (certified for use in Canada) and used within its rating and marking (Rule 2-024 and related rules). Equipment must be marked with its ratings, such as voltage, current and the manufacturer, and the 2024 edition added a requirement to mark the maximum permitted load (Rule 2-100). Installing equipment contrary to its certification or instructions, for example using a breaker in a panelboard it is not certified for, is a code violation.

Workmanship and connections

Work must be done in a neat and workmanlike manner. Connections are the weakest points of any installation and cause many electrical fires. Terminals must be suitable for the conductor material (copper, aluminum or both, marked for example "AL7CU" or "AL9CU"), the number of conductors per terminal must be within the terminal's rating, and terminals must be tightened to the torque specified by the manufacturer. Conductor temperature ratings must suit the terminal temperature rating (usually 60 °C or 75 °C), which limits the ampacity that can be used (Rule 4-006 and Lesson 4).

Loose connections heat up under load: the resistance of a poor joint turns current into heat, which oxidizes the contact, which raises resistance further. A connection that is fine on day one can fail years later. Torque specifications exist precisely to prevent this.

Identification of conductors

Conductor colours are not a matter of preference:

• The identified (neutral) conductor must be white or grey (Rule 4-036). White or grey insulation must not be used for any other purpose, except where the code specifically permits re-identification, such as a white conductor in a cable used as a switch leg and marked accordingly.
• Bonding conductors must be bare, or have green insulation, or green with one or more yellow stripes (Rule 4-038).
• Ungrounded (hot) conductors use other colours. For single-phase systems, black and red are normal; for three-phase systems, red, black and blue are used for phases A, B and C (Rule 4-038).

Locations and enclosures

Equipment and enclosures must suit their environment. Enclosures are rated by type numbers that indicate their protection against dust, water, ice and corrosion. Common types include:

A panelboard installed outdoors in a Type 1 enclosure, or a Type 3R enclosure in a food plant washed down daily with hoses, is a violation even if every wire inside is correct.

Working space

Equipment that may need examination, adjustment, servicing or maintenance while energized, such as panelboards, switchboards and motor control centres, must have clear working space in front of it so that a worker can do the job and escape quickly if something goes wrong. The space must be kept clear; storage in front of a panel is one of the most common violations found in existing buildings.

The CEC requires a minimum working space of 1 m in front of such equipment, with adequate headroom, and the space must not be used for storage (Rule 2-308). Equipment likely to be worked on while energized must also be marked to warn of shock and arc flash hazards (Rule 2-306).

Protection of live parts and interrupting ratings

Live parts must be enclosed or guarded so that people cannot accidentally contact them. Unused openings in panels and boxes must be closed with approved fillers; missing knockouts and breaker filler plates are frequent findings. Every overcurrent device must also have an interrupting rating at least equal to the fault current available where it is installed; a residential breaker rated 10 kA installed where 22 kA is available could fail violently during a fault. ELEC-320 returns to fault current and coordination; for now, remember that equipment ratings include more than just amperes and volts.

The general rules of this lesson are applied to branch circuits in Lesson 3 and to devices and panelboards in Lessons 7 and 8.