It's essential to select the appropriate electrical cable cross-section to comply with current electrical standards. You can't arbitrarily choose a cross-section, particularly for safety reasons. Careful consideration is required regardless of the protective sheath.
Note that cross-sections differ between AC and DC cables:
- Between 50 and 1000 Volts for alternating current
- Between 120 and 1500 Volts for direct current
Essential Criteria for Choosing Cable Cross-Section
To select the perfect cable cross-section for your electrical circuit, determine:
- Cable length
- Circuit type
- Maximum circuit breaker rating
- Installation method
Cable Cross-Section and Voltage Drop
Homes supplied by public networks may be located some distance from the connection point. Longer cables create greater voltage drops. Generally, it's recommended not to exceed 3% voltage loss for lighting and 5% for other installations when protection and metering aren't located near the source. Beyond these values, the cable must be resized according to the installation.
Using Charts for Selection
Electricians and DIYers can use an abacus table to choose the correct cable cross-section based on power consumption or current draw and electrical line length. This is particularly useful when connecting outbuildings to your main residence (garage, summer kitchen, swimming pool, etc.).
Pay attention to the current carrying capacity of the cable according to installation method and cable type.
Installation Methods
For underground installation, cables can be selected directly from the chart.
For other installations, consider various installation methods before determining admissible current from the table.
After determining the admissible current, apply a correction factor of approximately 0.7. Then, verify that the circuit breaker will protect the cable against short-circuiting.
Common Domestic Installation Scenarios
Here are typical situations with maximum protection ratings and minimum cross-sections:
| Type of Line/Circuit | Maximum Protection Rating | Minimum Cross-Section |
|---|---|---|
| Lighting | 16 A max | 1.5 mm² |
| Single electrical socket | 20 A | 2.5 mm² |
| Specialized electrical socket (washing machine, dishwasher) | 20 A | 2.5 mm² |
| Oven, cooker or hob power supply | 32 A | 6 mm² |
| Water heater | 20 A for power / 2 A for control | 2.5 mm² for power / 1.5 mm² for control |
| CMV | 2 A (except special cases) | 1.5 mm² |
| Heating (wall) | 20 A max (except special cases) | 1.5 to 6 mm² depending on power |
| Heating (floor) | 32 A max (except special cases) | 1.5 to 10 mm² depending on power |
| Power supply from meter | 30 to 90 A max | Circuit breaker 30-60 A: 16 mm² / Circuit breaker 90 A: 25 mm² |
Electrical Wire Color Codes
When choosing wire for a power outlet, remember these color codes:
- Earth wire: Green or Yellow
- Neutral: Blue
- Live: Red, Black, or Brown
- Shuttle: Purple or Orange
- Can never be green, yellow, blue, red, brown, or black
- Pilot wire (for electric heating): If the live wire is brown, it will be black, or vice versa
