What is the purpose of CE Code Rule 4-004?

Rule 4-004 sets the minimum ampacity required for conductors based on the load they carry, before applying overcurrent protection rules in Section 14.

Which tables does Rule 4-004 reference?

Tables 1 through 4 list ampacities for various conductor materials and temperature ratings, subject to the correction factors in Rules 4-006 and 4-008.

Published April 5, 2026

CE Code Rule 4-004: Conductor Ampacity

Rule 4-004 is the foundation of every wire sizing decision in Canada. It requires that conductor ampacity be sufficient for the load, corrected for the way the conductor is installed. When electricians search for a conductor ampacity calculator Canada, they are ultimately trying to satisfy this rule efficiently.

What Rule 4-004 requires

Conductors must have an ampacity not less than the maximum current they will carry, as adjusted by Rules 4-006 (temperature) and 4-008 (bundling). The base values come from Tables 1–4 depending on material and insulation rating.

Relationship to other rules

Rule 4-006: Ambient temperature correction (Table 5A)
Rule 4-008: Conductor bundling derating (Table 5C)
Rule 8-102: Voltage drop may require larger conductors than ampacity alone
Rule 14-104: Overcurrent device sizing relative to conductor ampacity

Use the free calculator

Our conductor sizing calculator applies Rule 4-004 with derating and voltage drop in one workflow. For broader context, see the wire size guide for Canada.