Plug Wire Diagram

Plug Wire Diagram — interactive diagram. Open it in the editor to customise components and wiring.

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

A plug wire diagram illustrates the internal layout of a mains plug, identifying which conductor colour connects to which terminal pin — live (brown), neutral (blue), and earth (green/yellow) — and where the fuse sits in the circuit path.

A plug wire diagram serves as a reference for anyone replacing a damaged plug, shortening a cord, or verifying an existing connection. Unlike a full circuit diagram, the scope is narrow: from the point where the flex cable enters the plug body to the three pins that insert into the wall socket.

Despite this narrow scope, the diagram carries critical information. The most important principle is that the live conductor (brown) must connect to the live terminal — and only that terminal. The live terminal is the one in series with the fuse in a BS 1363 plug. If the live and neutral are reversed, the fuse is placed in the neutral path. A fault that blows the fuse will leave live voltage present at the appliance's internal wiring, even though the fuse has nominally disconnected the circuit.

A plug wire diagram should illustrate the following clearly: 1. The physical shape and orientation of the plug body (BS 1363, NEMA, Schuko, or other) 2. The three pins labelled with their function (L, N, E) 3. The wires entering the plug with their colours 4. The fuse (where applicable) shown in series with the L pin 5. The cord grip clamping the outer sheath 6. The earth wire drawn slightly longer than the others — this is intentional, so it is the last to disconnect if the cord is yanked

One detail most diagrams omit: the internal sequencing of connections when wiring. Best practice is to connect earth first, then neutral, then live — so that if the plug is accidentally energised during the process (for example, if someone plugs it in before you have closed the body), the first thing connected is the earth, which is at zero potential. The live is connected last.

Different countries use different wire colours, but the logic is consistent: one conductor is at supply potential (live), one is the return path (neutral), and one is the protective earth for fault safety. Always verify the colour code for your country's applicable standard before working on any mains-voltage connector.

How to wire plug wire diagram

Confirm the plug type and applicable standard Identify the country of use and the applicable standard: BS 1363 (UK), NEMA 5-15 (USA/Canada), AS/NZS 3112 (Australia/NZ), Schuko CEE 7/4 (Europe). Each has different pin geometry, terminal locations, and colour conventions. A diagram that applies to one standard does not necessarily apply to another.
Remove the old plug or prepare the cable end If replacing a plug, cut the cable just behind the old plug and discard the old plug body. If preparing a fresh cable end, trim to length. Remove the outer sheath, exposing the three inner conductors. Strip 8 mm of insulation from each conductor. Twist wire strands tightly.
Thread cable through the plug back shell Before making any connections, thread the cable through the plug's cord grip or cable anchor. This step is frequently skipped and then the plug cannot be closed without disconnecting everything and starting again.
Connect earth (green/yellow) to the E terminal Ensure the earth conductor is slightly longer than the others. Insert into the E terminal, tighten the screw, and tug to verify. On a screw-barrel terminal, the bare wire coils around the shaft; on a pillar terminal, it inserts into the hole and is clamped by the screw.
Connect neutral (blue) to the N terminal Insert the blue conductor into the N terminal. Tighten. No bare copper should protrude beyond the terminal body. Tug to verify. On BS 1363 plugs, the N terminal is on the left when viewed from the rear (earth pin at top).
Connect live (brown) to the L terminal and check the fuse Insert the brown conductor into the L terminal and tighten. For BS 1363 plugs, confirm the fuse is in the fuse carrier between the L terminal and the L pin. Fit the correct rating fuse: 3 A for low-power appliances (up to 700 W), 13 A for high-power appliances.
Tighten the cord grip and close the plug Tighten the cord-grip screws or nut so the outer sheath is firmly clamped. Close the plug body and tighten the retaining screw. Test with a plug tester before connecting to a live socket.

Specifications

UK fused plug (BS 1363)	13 A max, 250 V AC; fused live terminal with BS 1362 cartridge fuse
Live conductor colour (IEC 60446)	Brown (post-2006 harmonisation)
Neutral conductor colour	Blue
Earth conductor colour	Green and yellow stripes
Old UK colour code (pre-2006)	Red = live, Black = neutral, Green = earth
North American colour code (NEMA)	Black (or red) = hot/live; White = neutral; Green or bare = earth
Cord sizes (typical)	0.75 mm² (up to 6 A); 1.0 mm² (up to 10 A); 1.5 mm² (up to 16 A); 2.5 mm² (up to 25 A)
Earth wire length inside plug	Slightly longer than live and neutral — last to disconnect under tension

Safety warnings

A mains plug is a live-voltage component. Never open, modify, or wire a plug while it is inserted in a wall socket. Always disconnect before starting work.
Only use plugs and flex certified to the applicable national standard. Uncertified or counterfeit plugs may have undersized pins, inadequate insulation, or incorrect fusing — all of which present fire and shock risks.
All wiring in a mains plug must comply with applicable standards. For fixed installation work, a licensed electrician must carry out or inspect the work in accordance with BS 7671, NEC/NFPA 70, AS/NZS 3000, or IEC 60364, as applicable.
Do not use a plug with a cracked body, loose pins, or scorched terminals. These are unrepairable conditions — replace the plug. A loose pin in a socket generates heat and is a fire risk.

Tools needed

Flat-blade screwdriver (plug retaining and terminal screws)
Wire stripper (matched to conductor cross-section)
Side-cutter pliers
Plug tester (socket tester) or multimeter
Tape measure (for measuring strip lengths accurately)

Common mistakes

Connecting brown wire to the N (neutral) terminal and blue wire to L — this puts the fuse in the neutral rather than the live path.
Forgetting to thread the cord through the cable grip before making connections, requiring all connections to be redone.
Leaving copper strands protruding from terminals, creating risk of inter-terminal contact and short circuit.
Fitting a 13 A fuse on an appliance rated at under 100 W — the fuse provides no meaningful protection for that load.
Not tightening the cord grip, allowing the conductors to bear mechanical load from cable pulling — this typically results in the live conductor pulling off its terminal.

Troubleshooting

Appliance does not power on after plug replacement: Cause: Loose or disconnected terminal; blown fuse during installation; live and neutral transposed causing RCCD trip Fix: Test the plug with a socket tester. Check fuse continuity with a multimeter. Re-open the plug and tug each terminal connection. Verify correct L/N/E conductor routing per the diagram.
Plug gets hot at the fuse carrier: Cause: Poor contact between fuse end cap and fuse carrier spring, or the fuse is overrated for the load and carrying excessive current Fix: Replace the fuse with one of the correct rating. Inspect the fuse carrier clips for spread or corrosion. If the carrier is damaged, replace the plug body.
Plug tester shows earth not connected: Cause: Earth conductor not inserted into the terminal, screw not tightened, or earth pin is bent and not making contact inside the socket Fix: Open the plug, re-verify the green/yellow conductor is secured to the E terminal with the screw tightened. Inspect the earth pin for damage. Replace if the pin is bent or corroded.

Frequently asked questions

What is the correct order to connect wires in a plug?

Connect earth first, then neutral, then live. This sequence ensures that if the partially assembled plug were accidentally energised, the live terminal — the most hazardous — is connected last. When disconnecting, reverse the order: remove live first, then neutral, then earth last.

Why is the earth wire cut longer than the live and neutral inside the plug?

If the cord is pulled hard enough to drag through the cord grip, the conductors are pulled toward the plug pins. By making the earth conductor slightly longer, it is the last wire to disconnect under mechanical stress — ensuring the appliance remains earthed for as long as possible during a cable pull-out event.

What happens if you wire a plug with no earth connection?

For a Class I (earthed) appliance, omitting the earth connection means that if a live conductor touches the metal case internally, the case becomes live at mains voltage. Anyone touching the case while standing on ground completes the circuit through their body. This is a potentially fatal shock hazard.

How do I know which terminal is live (L) and which is neutral (N) on an unfamiliar plug?

Check the plug body for terminal markings (L and N, or colour-coded terminal screws). On a BS 1363 UK plug, the live terminal (L) is on the right when viewing the rear of the plug with the earth pin at the top. On NEMA 5-15 (North America), the brass screw is live (hot), the silver screw is neutral.

Can old colour codes (red, black, green) still be found in UK plugs?

Yes. Pre-2006 UK wiring used red for live, black for neutral, and green (single colour) for earth. These are still found in older appliances and should be connected as: red to L, black to N, green or green/yellow to E. Never assume old colour codes match new standards in unfamiliar equipment.