Adiabatic Equation for Copper cable

Name: Wilson Electrics
Price range: $$$

⚡ About This Tool

Copper PVC – CPC Sizing Tool is a quick reference calculator for UK electricians and engineers. Use it to:

• 🧮 Calculate Zₛ (earth fault loop impedance)
• ⚡ Find the prospective fault current (Iₐ)
• 📏 Size copper CPC (earth) conductors with the adiabatic equation

The tool follows BS 7671 guidance and assumes copper conductors with PVC insulation (k = 143). It’s designed for domestic and small commercial work. Always confirm results with the latest IET Wiring Regulations.

🚨 Disclaimer

This tool is for information and guidance only. It does not replace professional judgment, on-site testing, or reference to the current IET Wiring Regulations (BS 7671).
While every effort has been made to ensure accuracy, no liability is accepted for any errors, omissions, or the results of calculations.
Users remain responsible for ensuring all electrical work complies with legal and regulatory requirements.

Copper PVC – CPC Sizing Tool

Step 1: Calculate Zₛ (Earth Fault Loop Impedance)

R₁ (Line conductor resistance): R₂ (CPC resistance):

— OR —

R₁ + R₂ (combined resistance): Zₑ (External earth loop impedance):

Step 2: Calculate Fault Current (Iₐ)

U₀ (Nominal Voltage): Zₛ (from Step 1):

Step 3: Calculate CPC Size (Adiabatic Equation)

Iₐ (from Step 2): Disconnection Time (t) in seconds:

k = 143 (fixed for copper with PVC insulation)