Cable sizing

Every constraint solved together — capacity after correction factors, voltage drop and disconnection time. Change any input and the answer updates instantly.

Circuit inputs

Installation type

Circuit preset

Topology

Supply

Load (kW)

Power factor

Diversity (App A)

Run length (m)

Cable construction

Conductor material

Nature of load

Installation method (Table 4A2)

Insulation

Ambient (°C)

Circuits grouped

Thermal insulation

Protective device

Device rating (A)

Disconnection time

Volt drop limit (%)

Ze (Ω)

Socket outlets on this circuit

Reg 411.3.3 — additional protection up to 32 A

Cable concealed < 50 mm in a wall

Reg 522.6.202

30 mA RCD fitted

Reg 415.1.1 — additional protection

AFDD fitted

Reg 421.1.7 — arc fault detection

Device guidance

Suggested: MCB Type B · RCD Type A

General mixed load — a Type B curve suits socket and small power circuits. Type A RCDs are the minimum for circuits with electronic equipment (Reg 531.3.3).

Design current Ib = 20.0 A

Result

Run the BS 7671 check to size this circuit.

Tabulated values cover copper conductors for the listed installation methods. Results are a design aid only — verify against the current edition of the wiring regulations before issuing a design. See the terms & engineering disclaimer.