3-Pin Plug and Socket Wiring Diagram

3-Pin Plug and Socket Wiring Diagram — interactive diagram. Open it in the editor to customise components and wiring.

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

Clear wiring reference for 3-pin mains plugs and sockets showing Live, Neutral, and Earth terminal positions, conductor colours, and fuse selection for BS 1363 and comparable systems.

A 3-pin mains plug and socket provides a safe, earthed connection between portable appliances and the fixed mains supply. The three pins carry three distinct electrical functions: Live (L) delivers the supply voltage; Neutral (N) is the return conductor at near-earth potential; and Earth (E) is the protective conductor that provides a safe fault current path to prevent electric shock if an appliance casing becomes live.

In the United Kingdom and many territories that follow BS 1363, the plug is polarised and fused. The three pin assignments are: Live — top-right pin (smaller, brass, connected to the brown conductor and the fuse); Neutral — top-left pin (smaller, brass, connected to the blue conductor); Earth — top centre pin (largest, longest, connected to the green-and-yellow conductor). The earth pin is longest so it engages first and disengages last as the plug is inserted and removed — ensuring earth continuity before any live parts become accessible. A cartridge fuse (rated 1 A, 2 A, 3 A, 5 A, 7 A, or 13 A) in the plug protects the appliance flex and provides appliance-specific overcurrent protection.

In other regions using different standards — such as IEC 60884 (international), AS/NZS 3112 (Australia/New Zealand), SANS 164 (South Africa), or NEMA 5-15 (North America) — the physical pin geometry differs but the L/N/E functional assignments remain consistent. Conductor colour conventions also vary: in IEC 60446 (widely adopted), brown = Live, blue = Neutral, green-yellow = Earth. In older installations (pre-2004 in the UK) the colours were red = Live, black = Neutral, green = Earth — re-terminating old appliances requires care to avoid misidentification.

The socket outlet provides the corresponding female receptacle, with internal spring contacts for each pin. In BS 1363 sockets, internal shutters block the Live and Neutral apertures unless the Earth pin is simultaneously engaged, providing a critical safety barrier against children inserting objects into live sockets.

How to wire 3 pin plug socket diagram

Select the correct flex and fuse for the appliance Confirm the appliance power rating (watts) from the rating plate. Select a flex cross-section rated for the current draw (0.5 mm² for up to 3 A; 0.75 mm² for up to 6 A; 1.0 mm² for up to 10 A; 1.25 mm² for up to 13 A). Choose the matching fuse rating: 3 A for appliances ≤ 700 W, 13 A for appliances > 700 W.
Remove the plug cover and prepare the flex Unscrew the plug cover screw. Loosen or remove the cord grip. Feed the flex through the cord grip opening. Strip the outer sheath back 35–45 mm — take care not to nick the inner conductor insulation. Strip each inner conductor 5–8 mm at the tip.
Identify and prepare the conductors Identify each conductor by its insulation colour: brown = Live, blue = Neutral, green-and-yellow = Earth. Twist the strands of each conductor clockwise so no loose strands protrude. For solid-pin plugs that use cord-grip pillar terminals, folding the stripped end back on itself doubles the contact area.
Connect the Earth conductor first Connect the green-and-yellow (Earth) conductor to the Earth terminal — the top-centre, largest pin. The Earth lead inside the plug must always be longest, so it does not pull tight before the other conductors if the flex is tugged. Tighten the terminal screw securely.
Connect Neutral and then Live Connect the blue (Neutral) conductor to the top-left terminal (N). Connect the brown (Live) conductor to the top-right terminal (L). Tighten both terminal screws firmly. In BS 1363 plugs, the Live terminal also contains the cartridge fuse — ensure the correct fuse is fitted before wiring or replace it now.
Secure the cord grip and check the wiring Position the flex in the cord grip so that the grip clamps the outer sheath — not the individual conductors. Tighten the cord grip screws firmly. Visually inspect that no bare conductor strands are visible outside the terminals and that all terminal screws are tight. No conductor should be able to be pulled from its terminal with light hand pressure.
Close and test the plug Refit the plug cover and tighten the cover screw. Plug into a socket and use a plug tester (polarity and earth continuity tester) to verify correct connections. Plug testers provide a go/no-go indication for correct wiring, reversed polarity, and missing earth — available at most electrical hardware retailers.

Specifications

Standard (UK/British territories)	BS 1363 (plug); BS 1362 (cartridge fuse); BS 7671 (installation)
Rated current	13 A maximum (BS 1363)
Rated voltage	250 V AC
Conductor colours (IEC 60446 / post-2004 UK)	Live = brown; Neutral = blue; Earth = green-and-yellow
Conductor colours (pre-2004 UK / older installations)	Live = red; Neutral = black; Earth = green
Fuse ratings available (BS 1362)	1 A, 2 A, 3 A, 5 A, 7 A, 10 A, 13 A
Flex cross-section selection	0.5 mm² ≤ 3 A; 0.75 mm² ≤ 6 A; 1.0 mm² ≤ 10 A; 1.25 mm² ≤ 13 A (typical — verify with cable manufacturer derating tables)
Shutter requirement (socket)	Shuttered Live and Neutral apertures mandatory (BS 1363 sockets); shutters open only when Earth pin engages

Safety warnings

Always isolate the circuit at the consumer unit (fuse board) and verify dead with a calibrated voltage tester before working on any fixed socket outlet. Work in accordance with BS 7671 (IEC 60364) or the applicable national wiring regulations for your region.
Never connect the Live conductor (brown) to the Neutral terminal or vice versa. Reversed polarity leaves the appliance switch in the neutral conductor, meaning the appliance remains live at the body even when switched off — a potentially fatal shock hazard.
Never omit the Earth conductor on a Class I appliance (any appliance with an exposed metal casing). Without an Earth connection, a fault that makes the casing live will not be cleared by the protective device and presents a serious electric shock risk.
Do not leave any bare conductor strands exposed outside the terminal clamps. A stray strand touching the wrong terminal can cause a short circuit, sparking, fuse failure, or fire.
In many countries, fixed socket outlet wiring must be carried out by or inspected by a registered or licensed electrician. DIY plug wiring is generally permitted for the flexible cord only. Check local regulations before carrying out any fixed wiring work.

Tools needed

Insulated flat-blade screwdriver (3 mm) for plug terminal and cord grip screws
Wire strippers for 0.5–1.5 mm² flex conductors
Plug tester (socket tester with polarity, earth, and wiring indicators)
Calibrated voltage tester (non-contact or two-probe type for fixed socket work)
Small side-cutting pliers for trimming conductor ends cleanly

Common mistakes

Connecting the brown Live conductor to the Neutral terminal and the blue Neutral conductor to the Live terminal (reversed polarity) — this leaves appliance switches in the neutral conductor, a dangerous condition that is not always immediately apparent.
Allowing the cord grip to clamp on the inner conductors rather than the outer flex sheath — if the flex is pulled, the inner conductors bear the tension and can pull out of the terminals, creating an arc or short circuit inside the plug.
Leaving stray wire strands protruding from terminals — a single stray strand can bridge to an adjacent terminal, causing a short circuit within the plug body that may not blow the fuse immediately but will cause overheating.
Fitting a 13 A fuse in a plug connected to a low-power appliance — a 13 A fuse will not blow on a fault that draws only 2 A, meaning the flexible cord could overheat without fuse protection; always match fuse to appliance rating.
Re-using the original fuse when rewiring a plug without checking its rating — plugs from appliances of different wattages have different fuse values; always check and replace with the correct rating for the current appliance.

Troubleshooting

Appliance does not work from the socket: Cause: Blown plug fuse, poor terminal connection inside the plug, or faulty socket outlet Fix: Remove the plug and check the cartridge fuse by fitting a known-good fuse. If the new fuse blows immediately on plug-in, an appliance fault is likely. If the original fuse was intact, open the plug and check all three terminal screws are tight and conductors are seated correctly.
Plug tester indicates reversed polarity: Cause: Live (brown) and Neutral (blue) conductors connected to the wrong terminals Fix: Remove the plug from the socket, open the plug body, and swap the brown conductor to the Live (right) terminal and the blue conductor to the Neutral (left) terminal. Re-test with the plug tester before use.
Plug tester indicates missing earth: Cause: Earth conductor not connected, connection loose, or conductor broke inside the sheath due to repeated flexing Fix: Open the plug and verify the green-and-yellow conductor reaches the Earth terminal and the terminal screw is tight. If the conductor is intact but not reaching the terminal, shorten the flex at the plug end and re-terminate. If the conductor has failed inside the sheath, replace the entire flex.

Frequently asked questions

Which pin is Live, Neutral, and Earth in a standard 3-pin plug?

In a BS 1363 (UK) plug: Live (L) is the top-right pin (brown conductor); Neutral (N) is the top-left pin (blue conductor); Earth (E) is the top-centre pin — the longest — (green-and-yellow conductor). Always verify against the wiring diagram inside the plug body and the standard applicable in your country.

Why is the Earth pin longer than Live and Neutral on a BS 1363 plug?

The Earth pin engages first on insertion and disengages last on removal. This ensures the appliance casing is earthed before any live connections are made, and remains earthed until the live connection has been broken — protecting against electric shock if an internal fault makes the casing live at the moment of disconnection.

What fuse should I fit in a 13 A plug?

Fit the fuse appropriate for the appliance wattage, not always the maximum 13 A. The rule of thumb: divide appliance watts by 230 V to get amps; round up to the next standard fuse rating (3 A for appliances up to 700 W; 13 A for appliances over 700 W). Always check the appliance instructions for the manufacturer's specified fuse rating.

What do the conductor colours mean in a 3-pin plug?

Under IEC 60446 (used in the UK from 2004 and across Europe): brown = Live, blue = Neutral, green-and-yellow = Earth. In older UK wiring (pre-2004): red = Live, black = Neutral, green = Earth. In North American wiring: black = Live (hot), white = Neutral, green or bare = Earth (ground).

Is it safe to wire a 3-pin plug without an earth connection?

Only for double-insulated appliances (Class II), which have no exposed metal parts requiring earthing. Double-insulated appliances are marked with a double-square symbol and typically use a 2-core flex. For Class I appliances (with metal casings), the Earth connection is mandatory for safe operation. Never omit the Earth from a Class I appliance.