08-02 Conductor sizing

Electricity produces Heat

Current flowing through wire = heat
More heat ⚡ → higher temperature 🌡️
✅ combustion🔥
✅ melting🧊
✅ denaturing🍳
❌ melted wire insulation🧊 (short circuit, shock hazard, etc.)
❌ melted plastic🧊 (switch, plug, connector, appliance, etc.)
❌ flammable materials ignite🔥

Thermal Equilibrium

How to decrease heat produced?

• Lower resistance (Watt's Law)
  • Copper instead of Aluminium
  • Thicker copper
• Lower current (Watt's Law)
  • Lower power
• Less time
• Wider contact surface

How increase heat dissipation?

• Better air circulation
• Lower ambient temperature
• Unbundled conductors

Sizing of Conductors

See this simplified summary of IEC 60364.
Or make a copy of this Google Sheets calculator

Exercises

1. Describe the electrical installation of a 3.6kW instant water heater. Focus especially on cable/wire sizing, choice and sizing of switches, choice and sizing of connectors.
2. Describe the electrical installation of a 2300W induction cooker for a hotpot dinner. Focus especially on cable/wire sizing, choice of extension strips, choice of power source.

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