How to Wire a Plug
Updated: Oct 9
To wire a UK plug, connect brown to L, blue to N and green and yellow to E, fit the right fuse and clamp the outer sheath. It is one of the few electrical jobs many careful DIYers can do themselves, but only when it is a simple plug replacement and the cable is otherwise sound.
Before you start
Before doing anything, unplug the appliance completely. Wiring a plug is not notifiable building work and needs no sign-off, and HSE describes it as a simple task within the grasp of many people, but the flex must be dead: never open a plug that is still in a socket. Do not try to wire a plug if the cable is cut, nicked, crushed, taped up, scorched, or showing signs of overheating. Electrical Safety First says a lead should have no joints or insulating-tape repairs, and HSE treats taped joins and coloured wires showing at the plug as faults. A damaged lead should be replaced, not patched.
If the problem is the socket on the wall rather than the plug (scorch marks, a loose faceplate, a socket that feels warm), that is fixed wiring, and our socket and power installation work covers testing and replacing it.
What you need
You only need a few basics: a replacement UK 3-pin plug that meets BS 1363, a screwdriver, a wire stripper or small knife used carefully, and the correct fuse for the appliance. Electrical Safety First's plug and fuse checks say the plug should be marked BS 1363 on the back and the fuse should be a BS 1362 fuse of the correct size.
UK plug wire colours
For a modern UK plug, the wire colours are simple: brown = live (L), blue = neutral (N), and green/yellow = earth (E). Electrical Safety First also notes that older plugs may use red = live, black = neutral, and green = earth. If you come across those older colours and you are not fully confident, it is safer to stop and get advice rather than guess. Our post on what colour the live wire is covers the older colours and where they still turn up.
Plug wiring diagram (UK)
Take the cover off and look into the back of the plug, pins pointing away from you and the cord grip nearest to you. You will see three terminals:
Earth (E), top centre: the green/yellow wire goes to the large terminal at the top, which connects to the longer earth pin.
Live (L), bottom right: the brown wire goes to the terminal on the right, the one next to the fuse.
Neutral (N), bottom left: the blue wire goes to the terminal on the left.
An easy way to remember it is "bRown to bottom Right, bLue to bottom Left". The earth wire should be left slightly longer than the other two, so that if the flex is ever yanked hard, the earth is the last connection to pull free.
How a plug is wired: the parts of a plug
Knowing the parts makes the steps below easier to follow. A BS 1363 plug has:
Pins: three rectangular pins. The live and neutral pins have insulated sleeves at the base so fingers cannot touch live metal while the plug is half in the socket.
Terminals: the three screw or clamp connections for the L, N and E wires.
Fuse and fuse carrier: a BS 1362 cartridge fuse sits in clips between the live terminal and the live pin. It blows if too much current flows because of an overload or a fault, stopping the flex and appliance from overheating. It is not surge protection.
Cord grip: a bar or clamp at the base that holds the outer sheath of the flex, so a tug on the cable does not pull on the terminals.
BS 1363 marking: moulded into the plug, showing it was made to the British Standard.
How to wire a plug, step by step
Work through the steps in order: grip loosened first, fuse in last, then a final check before the cover goes back on.
Step 1: Open the plug and loosen the cable grip
Unscrew the plug cover and set the screw aside safely. Inside, you will see the three marked terminals: L, N, and E, along with the fuse and the cable grip. Loosen the cable grip first so the cable can sit properly when you reconnect it. If you are replacing an old plug, note which wire went where before you undo anything.
Step 2: Prepare the cable carefully
Strip back the outer sheath just enough to let the three inner wires reach their terminals neatly without stretching. Many plugs have a strip gauge moulded inside the cover or printed on the packaging: use it, and leave the earth wire the longest. Then strip a small amount of insulation from each inner wire so the copper can be secured under the terminal screw. The aim is a tidy fit: enough bare copper to fill the terminal, but none left exposed outside it. Twist the strands of each wire together so no stray strand can touch a neighbouring terminal. HSE's check for a correctly wired plug is that no bare wire is visible other than at the terminals.
Step 3: Connect each wire to the right terminal
Connect the brown wire to L, the blue wire to N, and the green/yellow wire to E. Tighten each terminal firmly so the wire cannot pull free, but do not overtighten and damage the conductor. Once tightened, give each wire a light tug to make sure it is secure. On a Class II appliance with only two wires, the earth terminal stays empty (see below).
Step 4: Tighten the cable grip on the outer sheath
This part is often missed. The cable grip must clamp the outer cable sheath, not the coloured inner wires. Its job is to stop any pull on the flex from straining the terminal connections inside the plug. Electrical Safety First says the cord clamp should hold the outer insulation securely with both screws tight, and that no coloured wires should be showing where the cable enters the plug.
Step 5: Fit the correct fuse
Most UK plugs use either a 3A or 13A fuse. Electrical Safety First's general guide is that appliances rated from 700 to 3,000 watts should have a 13A fuse; lower-powered items such as lamps, TVs and computers usually take a 3A fuse. If the appliance instructions or rating plate say otherwise, follow the manufacturer's information. Only ever replace a fuse with one of the same rating, and never fit a larger fuse just to stop it blowing.
Step 6: Reassemble the plug and do a final check
Before putting the cover back on, check five things: the wires are in the correct terminals, the terminal screws are tight, no bare copper is visible, the cable grip is holding the outer sheath, and the fuse is seated correctly. Then refit the cover securely. These are the same points Electrical Safety First and HSE list for checking inside a plug.
Which fuse: 3A, 5A or 13A?
Check the rating plate or the instructions first, then use the wattage as your guide:
3A (usually red): table and standard lamps, TVs, computers, games consoles, laptop and phone chargers, radios. Generally anything under about 700 watts.
5A: manufacturers have standardised on 3A and 13A, but 5A fuses are still used in some older equipment. Fit one only where the manufacturer specifies it.
13A (brown): kettles, toasters, irons, fan heaters, washing machines, dishwashers, tumble dryers, vacuum cleaners, microwaves. Anything from 700 up to 3,000 watts, the most a wall socket is rated for.
The fuse is sized to protect the flex, so a 3A appliance with a thin flex should never be given a 13A fuse. If a correctly rated fuse keeps blowing, the fuse is doing its job: the appliance or its flex has a fault.
To change a plug fuse, unplug the appliance, then either open the plug (rewireable) or prise out the fuse carrier on the underside (moulded). Pop the old fuse out of its clips, press in a new BS 1362 fuse of the right rating, and refit the cover or carrier before plugging back in.
Wiring a plug with only two wires
Some appliances have a flex with just a brown and a blue wire. These are double insulated (Class II) appliances, marked with a square inside a square on the rating plate. They do not need an earth, so connect brown to L and blue to N as normal and leave the E terminal empty. Do not add an earth wire or connect anything to the earth terminal. The cord grip matters even more here, because the flex is often thinner.
Moulded plugs
Most new appliances come with a moulded plug that is sealed and cannot be opened or rewired. You can still change the fuse through the removable carrier on the underside. If the flex is damaged right next to a moulded plug, the usual fix is to cut the plug off below the damage and fit a rewireable one; if the damage is anywhere else along the lead, the lead needs replacing. If you cut one off, take the fuse out and throw the old plug away straight away. A cut-off moulded plug with bare wires can still be pushed into a socket, and that is a real shock risk, especially with children around.
Plug or fixed wiring?
The plug belongs to the appliance and its flex; the socket is part of the fixed wiring running back to the consumer unit. Replacing a socket like-for-like is not notifiable under Part P, but a new circuit, or work within the zones around a bath or shower, is notifiable and must be done by a registered electrician who can self-certify it. Our guide on how to wire a plug socket covers the socket side.
What to do after wiring the plug
When the plug is back together, plug it in and switch the appliance on while staying nearby. If the plug becomes hot, the fuse blows, you smell burning, or the appliance trips the electrics, stop using it immediately. At that point, the problem may be the appliance itself, the flex, or a wider electrical issue rather than the plug alone. That is where a professional inspection is the right next step, whether that means a quick visit, an emergency callout, or a broader EICR report if the property has recurring faults.
Plug wiring questions, answered
What fuse does a plug need?
A 3A fuse for appliances under about 700 watts, such as lamps, TVs and chargers, and a 13A fuse for appliances from 700 up to 3,000 watts. Follow the rating plate or instructions if they say otherwise.
Which terminal does the brown wire go to?
The live (L) terminal at the bottom right, next to the fuse, looking into the back of the plug with the cord grip nearest to you.
Can you rewire a moulded plug?
No. A moulded plug is sealed. If the flex is damaged next to it, cut the plug off below the damage, fit a rewireable plug, and throw the old one away straight away.
Our advice
At SM Electrical Midlands, our advice is simple: wiring a plug is a manageable DIY job when it is just a straightforward replacement on a sound cable and you are confident with the wire colours and fuse choice. But the moment you see damaged insulation, unusual wiring colours, repeated blown fuses, sparking, or heat, it is time to stop and get expert help. We cover homes and businesses across the West Midlands, and you can contact us here if you want us to check the appliance, the socket, or the wider installation.
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