📖 Cable Ampacity Calculator
Cable ampacity is the maximum current-carrying capacity of a cable under specific conditions. This calculator determines the ampacity of copper and aluminum cables based on BS 7671 and NEC standards, considering installation method, ambient temperature, grouping, and insulation type.
📐 Ampacity Calculation Factors
- Base Ampacity: Current rating from tables (BS 7671 / NEC)
- Temperature Correction (Ca): Ambient temperature affects capacity
- Grouping Correction (Cg): Cables together derate each other
- Installation Method: Clipped, conduit, buried, free air
- Insulation Type: PVC (70°C), XLPE (90°C), Rubber (60°C)
📊 Copper Cable Ampacity Table (Clipped Direct)
| Size (mm²) | PVC (A) | XLPE (A) |
|---|
| 1.0 | 13 | 15 |
| 1.5 | 16 | 19 |
| 2.5 | 22 | 27 |
| 4 | 30 | 36 |
| 6 | 38 | 46 |
| 10 | 52 | 63 |
| 16 | 69 | 85 |
| 25 | 90 | 115 |
| 35 | 115 | 145 |
| 50 | 140 | 180 |
| 70 | 180 | 225 |
| 95 | 220 | 275 |
| 120 | 255 | 315 |
| 150 | 295 | 365 |
| 185 | 335 | 415 |
| 240 | 400 | 500 |
| 300 | 470 | 580 |
📌 Correction Factors
- Ambient Temperature (Ca): 30°C = 1.00, 35°C = 0.94, 40°C = 0.87, 45°C = 0.79
- Grouping (Cg): Single = 1.00, 2-3 cables = 0.80, 4-6 cables = 0.70
- Installation: Clipped = highest, Conduit = -15%, Buried = -20%, Insulated = -50%
❓ Frequently Asked Questions
What is ampacity? ▼
Ampacity is the maximum current that a cable can carry continuously without exceeding its temperature rating. It depends on cable size, material, insulation, installation method, and environmental conditions.
What is the ampacity of 2.5mm² cable? ▼
A 2.5mm² copper cable clipped direct has approximately 27A (XLPE) or 22A (PVC). In conduit, it's about 23A (XLPE) or 18A (PVC).
What is the difference between ampacity and current rating? ▼
Ampacity and current rating are often used interchangeably. Ampacity is the maximum current capacity under specific conditions. Current rating is the same concept but may refer to the cable's rated capacity at a standard condition.
How does temperature affect cable ampacity? ▼
Higher ambient temperature reduces ampacity because the cable cannot dissipate heat as effectively. For every 10°C above 30°C, ampacity typically decreases by about 5-8%.