Domestic Circuit Types Guide
Standard UK domestic circuit types — ring finals, radials, lighting, cooker, shower, and EV circuits
Standard Domestic Circuit Types
A typical UK domestic installation uses a combination of ring final, radial, lighting, and dedicated appliance circuits — each with specific cable and MCB requirements.
Common domestic circuits at a glance
BS 7671 and IET On-Site Guide| Circuit | Cable | MCB | Notes |
|---|---|---|---|
| Ring final (sockets) | 2.5mm² T&E | 32A Type B | Standard socket circuit |
| Radial (sockets) | 2.5mm² T&E | 20A Type B | Smaller areas / extensions |
| Radial (sockets) | 4mm² T&E | 32A Type B | Alternative to ring final |
| Lighting | 1.5mm² T&E | 6A Type B | Max ~1200W per circuit |
| Immersion heater | 2.5mm² T&E | 16A Type B | 3kW dedicated circuit |
| Shower (9.5kW) | 10mm² T&E | 45A Type B | Dedicated circuit |
| Cooker | 6mm² T&E | 32A Type B | With diversity applied |
| EV charger (7kW) | 6mm² T&E | 32A Type B | Dedicated, RCD Type A min. |
Cable sizes assume Method C (clipped direct), 30°C ambient, no grouping.
Ring Final vs Radial Circuits
A ring final circuit starts and finishes at the same MCB terminals, forming a continuous loop. This allows 2.5mm² cable to be protected by a 32A device because current splits between both legs. A radial circuit runs from the MCB to the furthest point and stops — the cable must carry the full circuit current.
Ring vs radial comparison
IET On-Site Guide| Feature | Ring (32A) | Radial (20A) | Radial (32A) |
|---|---|---|---|
| Cable size | 2.5mm² | 2.5mm² | 4mm² |
| MCB rating | 32A | 20A | 32A |
| Spurs allowed | Unfused & fused | Yes | Yes |
| Floor area guide | ~100m² | ~50m² | ~100m² |
| Cable usage | Higher | Lower | Moderate |
Modern Trend — Radial Circuits
Dedicated Appliance Circuits
High-power fixed appliances require their own dedicated circuit from the consumer unit. Each circuit has its own MCB/RCBO and cable run.
Dedicated appliance circuit requirements
BS 7671 and manufacturer guidance| Appliance | Typical Load | Cable | MCB | Protection |
|---|---|---|---|---|
| Electric cooker | 8-15kW | 6mm² | 32A | RCBO Type A |
| Electric shower | 8.5-11kW | 10mm² | 45A | RCBO Type A |
| Immersion heater | 3kW | 2.5mm² | 16A | RCD 30mA |
| Storage heater | 1.7-3.4kW | 2.5mm² | 16A-20A | RCD 30mA |
| EV charger | 7.4kW | 6mm² | 32A | Type A / Type B RCD |
Lighting Circuit Design
Standard domestic lighting uses 1.5mm² T&E cable with a 6A Type B MCB, supporting approximately 1200W per circuit (just over ten 100W lamps or many more LEDs). With modern LED lighting drawing a fraction of traditional loads, a single lighting circuit can serve an entire floor.
LED Driver Inrush