Cooker Connection Units: Wiring a Hob, Oven or Range Cooker Correctly

The cable size, the circuit protection, and the connection unit are all interdependent, and all three are specified at first fix based on what kind of cooking appliance will eventually be fitted at second fix. Change the appliance plan after the cables are run, and you may be retro-fitting at exactly the point where the walls are closed and the worst time to start chasing in heavier cable. A single built-in oven, a separate induction hob, a combined hob-and-oven circuit, and a full-electric range cooker all draw different currents and need different circuits. This page explains what a cooker connection unit is, when one is required versus a cooker outlet plate, how to size the circuit for each common configuration, where to position the switch, and what to buy.

What a cooker connection unit is

A cooker connection unit (CCU) is a wall-mounted double-pole switch that provides the isolation point for a hardwired cooking appliance. It sits between the dedicated cooker circuit (fed by a 32A or 45A MCB at the consumer unit via 6mm or 10mm twin and earth cable) and the appliance's terminal block. Double-pole means the switch breaks both the live and the neutral when turned off, fully isolating the appliance rather than just interrupting the live.

That switch is the means of local isolation required by BS 7671 for any fixed appliance rated over 3kW. Unlike a plug socket, where pulling the plug isolates the appliance, a CCU is a permanent hardwired connection with no plug to pull, so the switch itself does the isolating job. Most CCU faceplates carry a neon indicator that glows when the unit is switched on. That neon matters more than it looks: an induction hob with a glass top and no power shows nothing, so the neon is often the only visible sign that the circuit is live before someone reaches behind a unit to work on the appliance.

Circuit sizing: four common configurations

The appliance determines the circuit, not the other way round. Read the appliance spec sheet for its kW rating before anyone fixes a cable size.

To read the spec sheet, find the total connected load in kilowatts (the rating plate or the installation manual lists it). The current the circuit must carry is simply the power divided by the supply voltage. Working at the UK nominal 240V, a 7kW oven draws 7000 / 240 = roughly 29A, comfortably inside a 32A MCB on 6mm cable. A 9.6kW range draws 40A and needs a 40A MCB. A 15kW professional-style range draws over 60A and may require its own dedicated 63A circuit run in larger cable. The arithmetic is trivial; the discipline is doing it before the cable is bought rather than assuming "the cooker cable" is one fixed thing.

P ÷ 240V

The current a cooker circuit must carry, in amps, is the appliance power in watts divided by 240. A 7kW appliance draws about 29A; a 9.6kW range draws 40A.

Where the CCU goes

The CCU must sit within arm's reach of the cooking appliance, within roughly 2m, so the user can isolate the appliance from where they stand at it without crossing the room. It is usually fixed at 1.8m to 2.0m on the wall next to the hob position, above the worktop and above the splashback. It must never go directly above the hob, where rising heat and steam would attack the switch and where reaching over a hot pan to isolate the appliance defeats the safety purpose entirely.

The other rule that catches people is access. The switch has to remain reachable once the kitchen is fully fitted. A CCU first-fixed at a sensible height can vanish behind a full-height larder unit or a tall fridge housing when the units arrive. Mark the appliance and unit layout on the same plan before the electrician sets out the position.

CCU versus cooker outlet plate

These two accessories do related but different jobs, and a typical installation uses one, the other, or both together.

A cooker outlet plate is a flush-mounted twin connection point with two cable glands. It terminates the circuit cable on one side and lets the appliance's own flexible cable exit on the other. It is used for appliances supplied with a pre-fitted flex, such as many range cookers, where the manufacturer expects the installer to connect the existing flex rather than wire into a terminal block. The outlet plate has no switch of its own, so a CCU sits remotely as the isolation switch on the wall.

The two can be combined in a single faceplate (switch plus outlet on one unit) or kept separate (outlet plate behind the appliance, switch at worktop height beside it). For a built-in hob or oven with no pre-fitted flex, you do not need an outlet plate at all: the CCU alone, wiring into the appliance terminal block, is the standard solution.

The 13A socket rule for combination installs

Where a separate oven and a separate hob are each rated below 3kW, and the combined load does not exceed 15kW, one permitted option is to run each appliance from an ordinary 13A socket on a ring or radial circuit rather than a dedicated cooker circuit. The 3kW threshold is the line BS 7671 draws for requiring fixed local isolation, and a fused 13A plug provides its own isolation when pulled.

In practice this option is shrinking. Most modern induction hobs pull well over 3kW and need a dedicated circuit and a CCU regardless. The case where the socket route still works is a small supplementary oven (a compact oven used for grilling or reheating) rated under 3kW. The simple test: if the appliance comes fitted with a UK 3-pin plug and its rating is under 3kW, a socket within reach of the appliance is permissible. If it exceeds 3kW, or it arrives with no plug, it needs a dedicated circuit with a CCU.

What to buy

A CCU is a low-cost accessory, so buy a recognised brand for the better switch mechanism and neon rather than saving a pound on the cheapest one. Match the rating to the circuit, not to the appliance you happen to be fitting first.

These are stocked by Screwfix, Toolstation, CEF, Edmundson Electrical, and every electrical wholesaler. Specify the CCU and outlet plate at the same time as your socket faceplates so the finishes match across the kitchen: flat white is standard, but brushed steel and chrome ranges all include a matching cooker unit if you want the wall accessories to coordinate.

External resource

IET Wiring Regulations (BS 7671) overview

The Institution of Engineering and Technology publishes BS 7671, the standard that governs cooker circuit isolation, cable sizing and the over-3kW rule. Your electrician works to this; the overview pages explain what the current edition requires.

electrical.theiet.org

Common mistakes

Undersizing the circuit cable for the actual appliance load. Running 6mm cable on a 45A circuit is dangerous: if a fault ever lets the full rated current flow, the MCB will hold long enough for the undersized cable to overheat. Always verify the cable size against both the MCB rating and the appliance load, not against one in isolation.

Concealing the CCU behind a tall unit. A switch that cannot be reached with the kitchen fitted is not providing isolation. Set the position against the final unit layout.

Fitting a 30A CCU on a 45A circuit. The switch must be rated for the circuit it isolates. A 30A unit on a 45A circuit is the wrong accessory and will be flagged on inspection.

Misreading dual-fuel range cooker requirements. On a dual-fuel range the gas hob runs from a gas supply, not the cooker circuit. Only the electric oven element draws power on the electrical side, so do not oversize the circuit expecting the whole appliance to be electric. Read the spec sheet and size for the electric load only.

Where you'll need this

• Kitchen electrical provisions, the cooker circuit and CCU position are set out here before the walls close
• First fix electrics, the 6mm or 10mm cable run from the consumer unit to the CCU happens at this stage
• Appliance selection, the appliance type you choose determines the circuit, cable and CCU rating, so decide it before first fix begins