CEC Conductor Sizing
Select the minimum conductor size per CEC Table 2 — accounting for temperature and bundling correction.
Inputs
Step-by-Step Calculation
1
Base load current
Iload = 40 A
2
Temperature correction factor — CEC Table 5A
At 30°C
(90°C rated):
Tf = 1.00
3
Bundling correction factor — CEC Table 5C
3 conductors:
Bf = 1.00
4
Corrected ampacity required
40 ÷ (1.00 × 1.00) = 40 A
5
Minimum conductor — first size rated ≥ corrected ampacity
#8
— rated
55 A
(90°C copper)
Conductor Cross-Section Comparison
Copper
Aluminum
Recommended
Recommended Conductor
#8
AWG
Rated 55 A — exceeds corrected requirement of 40 A
Copper
90°C
Tf 1.00
Bf 1.00
CEC Table 2 — Ampacity Reference
| Size | Copper (A) | Aluminum (A) | ||
|---|---|---|---|---|
| 60°C | 90°C | 60°C | 90°C | |
Temperature Correction Factors
CEC Table 5A — multiply base ampacity by factor for ambient temp
| Ambient Temp | 60°C Rating | 90°C Rating |
|---|
Bundling Correction Factors
CEC Table 5C — conductors in same raceway or cable
| Number of Conductors | Factor |
|---|
Always Round Up
If the corrected ampacity falls between two conductor sizes, always select the next larger size. Never round down.
Termination Ratings
T90 insulation offers higher ampacity but verify all terminals (lugs, breakers) are also rated for 90°C before using those values.
High Ambient Locations
Attics, boiler rooms, and outdoor southern exposures can reach 40–50°C. Always use the maximum expected temperature for that location.
Aluminum Considerations
Aluminum conductors require anti-oxidant compound and must use AL-rated connectors. They are typically two sizes larger than copper equivalent.