What cable size do I need for a 16A commando socket?

2.5mm² twin and earth is the standard choice for a 16A circuit in a domestic garage. Clipped direct it is rated at 27A under BS 7671 reference method C, giving adequate headroom. If the run is long (over about 25m) or the cable passes through insulation, check the voltage drop figure against BS 7671 Appendix 12 — 4mm² may be needed.

Does a garage socket need RCD protection?

Yes. BS 7671 Regulation 411.3.3 requires 30mA RCD protection on all socket circuits in garages, outbuildings and outdoors. The simplest way to achieve this on a new dedicated circuit is to use a 16A/30mA RCBO in the consumer unit, which gives both overcurrent and RCD protection in a single device.

Is fitting a new 16A commando circuit Part P notifiable?

Yes. Adding a new circuit is notifiable work under Part P of the Building Regulations in England. You must either use a Part P-registered electrician who can self-certify, or notify your local building control before starting and have the work inspected on completion. The socket itself, once the circuit exists, is a non-notifiable like-for-like replacement.

How to Fit a 16A Commando Socket in a Garage or Workshop (UK)

Fit a 16A commando socket in a garage or workshop

A blue 16A commando socket on a dedicated circuit lets you run a table saw, compressor, arc welder or caravan adaptor without pushing a ring main to its limits. The socket itself is simple to fit; the new circuit from the consumer unit is where the work and the Part P obligation sit.

Helpful video reference. Nick Bundy of N Bundy Electrical — a NAPIT-registered Staffordshire electrician — filmed this real garage workshop installation in February 2026: "Installing a 16 amp Socket in a Garage Workshop". He covers safe isolation of the consumer unit, RCBO selection and the cable run through the garage, which is exactly the sequence you need to follow.

Before you start. This job requires isolating the consumer unit's main switch, which takes down power across the whole house. Do it during daylight, let everyone in the house know, and have a torch to hand. A new circuit is Part P notifiable in England — if you are not Part P registered, you must notify your local building control authority before starting the work.

1. Plan the circuit and check consumer unit capacity

Open the consumer unit and check how many spare ways there are. You need one free slot for a 16A/30mA RCBO. If the board is completely full, you either need a tandem MCB arrangement (not always possible) or a separate garage consumer unit — at which point the job is more involved and you really want a qualified electrician doing it.

Also check the board type. Wylex, Hager and Crabtree boards generally accept their own brand of RCBO. A mismatched device can work but may not sit securely on the busbar — match the brand where you can.

2. Isolate the consumer unit and fit the new RCBO

Turn off the main switch. Confirm dead by testing the busbars with a voltage tester — the main switch does not disconnect the meter tails, so there is still live conductors in the top section of the board. Only work in the lower section below the main switch.

Clip the new 16A/30mA RCBO into the spare way. On most boards the RCBO clicks onto the busbar for the line terminal and its neutral goes to a dedicated terminal on the RCBO body rather than the neutral bar (that is what makes it an RCBO rather than a plain MCB). Leave the cable connections open for now — you will come back and connect the new cable once it is run.

3. Run the cable from consumer unit to garage

Use 2.5 mm² twin and earth for a standard 16A circuit up to about 25 metres. For longer runs, check the voltage drop calculation — you may need 4 mm².

Inside the house, run the cable in the void above the consumer unit or through the floor and up the outside of the building in weatherproof conduit. Through a cavity or solid wall, fit a wall sleeve and seal around the cable to prevent drafts. In the garage, surface-clip the cable in conduit or plastic trunking to protect it from mechanical damage.

4. Mount the commando socket enclosure

The 16A version is a blue BS EN 60309 socket with a round body and three pins in a keyway arrangement (2P+E, 6h position for 230V single-phase). Buy the surface-mounting version with its own enclosure — it includes the back box and the socket face as one unit.

Position it on the wall at a convenient working height, typically between 1.0m and 1.5m. Mark the fixing holes, drill and plug, then anchor the back box firmly. A loose socket that gets yanked by a heavy cable will pull away from the wall.

5. Terminate the cable at the socket

Feed the cable through the cable entry (use the size that grips the outer sheath, not the conductors). Strip back the outer sheath leaving around 80–100 mm inside the enclosure. Strip each conductor to the terminal depth — around 8 mm for screw terminals.

Connect brown (live) to L, blue (neutral) to N, and green-yellow (earth) to E. Tighten each terminal firmly. Pull each conductor gently after tightening to confirm there is no movement. Fix the socket face to the back box and close the enclosure.

6. Connect at the consumer unit and test

Make the final connections at the RCBO. Brown goes to the line terminal, blue to the RCBO's neutral terminal, green-yellow to the earth bar. Tighten fully. Restore the main switch.

Plug a socket tester into the new commando socket via an adaptor (13A to 16A adaptors are available from electrical wholesalers). All indicators should show correct polarity and earth presence. Then press the RCBO test button: it should trip. Reset it, and the circuit is ready to use.

Label the new RCBO in the consumer unit door schedule — something like "Garage 16A" is sufficient.

Stop and call an electrician if: the consumer unit has no spare ways, the board is old and does not accept RCBO devices, the cable run would pass through a fire compartment wall, you are not confident working inside a consumer unit, or you want the work certified under Part P without using building control notification.

When to call us

The socket side of this job is straightforward. The new circuit from the consumer unit involves working inside a live board (above the main switch) for a short period, which is where experience matters. Richard can run the circuit, fit the socket and issue a Minor Works Certificate for the job — all in a single visit to properties across east Kent.

Want a commando socket fitted in Sandwich?

Richard fits 16A and 32A workshop circuits across east Kent. Part P certification included as standard.

Contact Richard