Wiring a 3-Pin Plug: UK BS 1363 Colour Codes, Terminal Connections, and Fuse Selection

Wiring a 3-Pin Plug: UK BS 1363 Colour Codes, Terminal Connections, and Fuse Selection — interactive diagram. Open it in the editor to customise components and wiring.

This is a free printable wiring a 3 pin plug: download the diagram as SVG or open it and print to paper or PDF.

Wiring a 3-pin plug correctly means connecting brown to Live (right), blue to Neutral (left), and green/yellow to Earth (top), with the correct fuse fitted.

The UK standard 3-pin plug is defined by BS 1363. It is a distinctive large plug with three rectangular pins: a top earth pin (E, the longest), a right-hand live pin (L), and a left-hand neutral pin (N). The plug also contains an internal fuse in the live circuit — a feature unique among common international plug standards.

Under IEC harmonised wiring colours, now standard throughout the UK: - Live (L): brown conductor, connects to the right-hand pin terminal (when the earth pin is at the top) - Neutral (N): blue conductor, connects to the left-hand pin terminal - Earth (E): green and yellow striped conductor, connects to the top (longest) pin

Older UK appliance flex used the pre-harmonisation colours: red for live, black for neutral, and green for earth. These colours were replaced by the current harmonised scheme from 2004 onwards. If rewiring a plug on an older appliance with red, black, and green flex, the same terminal positions apply — red to live (right), black to neutral (left), green to earth (top).

The flex is secured inside the plug by a cord grip or clamp, which must grip the outer sheath of the cable, not the individual conductors. This relieves the mechanical stress on the terminal connections and is a critical safety feature: if the cable is pulled, the cord grip takes the load, not the wire terminals.

The internal fuse protects the flexible cord leading to the appliance. BS 1363 fuses are available in standard ratings: 1 A, 2 A, 3 A, 5 A, 7 A, and 13 A. Select the lowest rating that exceeds the appliance's normal current draw. For appliances rated up to 700 W, a 3 A fuse is generally appropriate. For appliances rated 700 W to 3 000 W (the maximum for a 13 A circuit), a 13 A fuse is used. Fitting a 13 A fuse on a lamp with thin flex offers almost no protection to that flex — the fuse should match the flex rating.

This article covers UK BS 1363. Other regions use different plug standards: Australia/NZ use AS/NZS 3112 (3-pin with flat angled blades), South Africa uses SANS 164 (round pins), and North America uses NEMA 1-15 or 5-15 (2 or 3 flat blade pins). Terminal assignments and wiring colours vary — always consult the applicable national standard.

How to wire wiring a 3 pin plug

Remove the plug cover Unscrew the central retaining screw on the plug face. Separate the two halves of the plug casing. Locate the three terminal screws and the cord grip.
Prepare the flex Using a cable stripper, remove approximately 50 mm of the outer flex sheath without cutting into the insulation of the individual conductors inside. Separate the three conductors: brown (live), blue (neutral), green/yellow (earth).
Strip the conductor insulation Strip approximately 8–12 mm of insulation from each conductor. Twist the strands of each conductor neatly. Do not leave any bare strand extending beyond the terminal that could contact adjacent parts.
Connect the earth conductor first Connect the green/yellow earth conductor to the top (earth, E) terminal — the terminal at the longest pin. Insert the stripped end under the terminal screw and tighten firmly. The earth conductor is typically the longest of the three because it must reach the top terminal.
Connect the neutral conductor Connect the blue neutral conductor to the left-hand terminal (N). Insert and tighten the terminal screw securely, ensuring no loose strands protrude.
Connect the live conductor Connect the brown live conductor to the right-hand terminal (L). This is the terminal connected to the fuse holder. Ensure the connection is secure.
Fit the fuse and secure the cord grip Insert the correct-rated fuse into the fuse carrier (usually clips between the live terminal and the live pin). Position the outer flex sheath under the cord grip and tighten the cord grip screws so the sheath is held firmly — check the cable cannot be pulled free. Reassemble the plug and tighten the cover screw.

Specifications

Standard	BS 1363 (UK plug); BS 1362 (fuse)
Rated voltage	250 V AC
Rated current	13 A maximum
Live terminal position (earth pin at top)	Right-hand terminal (L)
Neutral terminal position (earth pin at top)	Left-hand terminal (N)
Earth terminal position	Top terminal (E) — longest pin
Live conductor colour (IEC harmonised)	Brown
Neutral conductor colour (IEC harmonised)	Blue
Earth conductor colour	Green and yellow striped
Standard fuse ratings (BS 1362)	1 A, 2 A, 3 A, 5 A, 7 A, 13 A

Safety warnings

In the UK, rewiring a plug on an appliance is legal for the person using it; however, any rewiring of fixed wiring installations must be carried out by a competent person in accordance with BS 7671 (IEC 60364). These instructions cover portable appliance plug rewiring only.
Always isolate the appliance from the supply (remove from the socket) before opening the plug. Never work on a plug while it is inserted in a live socket.
Ensure the cord grip securely clamps the outer sheath of the flex, not the individual conductors. A loose cord grip is a significant fire and electric shock hazard.
Never use a 13 A fuse in a plug on an appliance with thin light-duty flex merely to avoid buying the correct fuse. An oversized fuse does not protect the flex from overheating.
This guide applies to UK BS 1363 plugs only. Wiring conventions, colour codes, and terminal arrangements differ for Australian (AS/NZS 3112), South African (SANS 164), North American (NEMA), and European (CEE 7) plug standards.

Tools needed

Flat-blade screwdriver (for terminal screws and cord grip)
Wire stripper
Side cutters
Fuse tester or continuity meter (to verify correct fuse rating)
Electrical insulating tape (for cable identification if needed)

Common mistakes

Connecting brown (live) to the neutral (left) terminal and blue (neutral) to the live (right) terminal — reversing live and neutral. The appliance may still work but the fuse is then in the neutral rather than the live, leaving the appliance live when switched off.
Forgetting to slide the cord grip under the outer sheath before making terminal connections, then being unable to fit the cord grip correctly on reassembly.
Leaving a tail of bare conductor sticking out beyond the terminal that can contact adjacent metal parts, causing a short circuit.
Using a 13 A fuse on a low-wattage appliance with thin flex, meaning the flex can burn out before the fuse responds.
Over-stripping conductor insulation so bare copper is exposed between the terminal block and the flex entry point.

Troubleshooting

Fuse blows immediately when appliance is plugged in: Cause: Appliance has an internal fault (short circuit), or fuse is rated below the appliance's starting current Fix: Try a new fuse of the correct rating. If it blows again immediately, the appliance likely has an internal fault and should not be used — have it inspected by a qualified repairer. Do not fit a higher-rated fuse to stop it blowing.
Appliance works intermittently or plug gets warm: Cause: Loose terminal connection or poor cord grip contact causing arcing Fix: Isolate, open the plug, check all terminal screws are tight and the cord grip is secure. Look for any discolouration or burning around terminals — a sign of arcing. Replace the plug if there is any evidence of damage.
Appliance works but RCD trips when it is plugged in: Cause: Live or neutral wire touching earth inside the plug, or appliance has an earth leakage fault Fix: Open the plug and check that no conductor is contacting the earth terminal or the metal earth pin. Check for pinched or damaged conductors. If wiring is correct, the fault is in the appliance.

Frequently asked questions

Which wire goes to which pin in a UK 3-pin plug?

In a UK BS 1363 plug, with the earth pin (E) at the top: brown (live) connects to the right-hand pin, blue (neutral) connects to the left-hand pin, and green/yellow (earth) connects to the top (earth) pin. A useful mnemonic: BRown = Bottom Right, BLue = Bottom Left, Green/Yellow = top.

What fuse should I use in a UK plug?

Choose the lowest fuse rating that still exceeds the appliance's normal running current. For appliances up to approximately 700 W, use a 3 A fuse. For appliances from 700 W to 3 000 W, use a 13 A fuse. The fuse protects the flex leading to the appliance, so matching the fuse rating to the flex's current capacity is as important as matching it to the appliance wattage.

Why must the cord grip clamp the outer flex sheath and not the individual wires?

The cord grip is designed to take the mechanical strain if the cable is pulled or tugged. If it only grips the individual conductors, a pull will stress the terminal screw connections, potentially loosening them and creating an arc or overheating hazard. The grip must securely clamp the outer sheath so the terminals only carry the electrical connection, not any tension.

Can I rewire any plug using these instructions?

These instructions cover the UK BS 1363 standard plug. Australia, New Zealand, South Africa, continental Europe, North America, and other regions use different plug standards with different pin arrangements, sizes, and wiring colour conventions. Never apply UK wiring colour codes or terminal assignments to a non-UK plug without consulting the relevant national standard.

What is the purpose of the earth pin being longer in a UK plug?

The earth pin is longer so it engages first as the plug is inserted. In UK socket shutters (the spring-loaded covers that block the live and neutral slots), the earth pin's insertion mechanically opens the shutters, allowing the live and neutral pins to enter only after the earth connection is established. This prevents accidental contact with live pins.