Calculate Cable Size ((better)) May 2026

Step 3: Apply the Voltage Drop Formula The basic DC / single-phase AC formula is:

| Condition | Derating Factor | | :--- | :--- | | Ambient 30-40°C (normal) | 1.00 | | Ambient 40-50°C (hot attic) | 0.87 | | 3-6 cables bundled | 0.80 | | 7-9 cables bundled | 0.70 | calculate cable size

You need at least 7.3 mm² . The nearest standard size is 10 mm² (since 6 mm² would be too small). Step 4: Adjust for Temperature and Grouping The formula above assumes ideal conditions. If cables run through hot attics or are bundled together, use these derating factors (from NEC/CEC tables): Step 3: Apply the Voltage Drop Formula The

A 2000W water heater on 230V. ( I = 2000 / 230 = 8.7 \text Amps ) Step 2: Determine the Round-Trip Cable Length Many forget this. If your device is 20 meters from the source, the actual electrical path is 40 meters (go and return). If cables run through hot attics or are

If your 5A fridge runs through a hot attic (0.87) and is bundled with 4 other cables (0.80): ( 5 / (0.87 \times 0.80) = 5 / 0.696 = 7.2A )

Now calculate cable size for , not 5A. Quick Reference: Common Cable Sizes & Current Ratings (Copper, 30°C) Use this as a starting point only—always verify with local codes.

Choosing the wrong cable size isn't just an inconvenience—it’s a fire hazard. Undersized cables overheat, melt insulation, and can cause voltage drops that damage your equipment.