UK Electrical Symbols
BS EN 60617 symbols for circuit diagrams, wiring plans, and layout drawings
Governing Standards
BS EN 60617 — Graphical symbols for diagrams (~1,900 symbols)
BS 7671 — Requires symbol use in certificates & circuit charts (Section 514)
BS 5839-1:2025 — Fire detection and alarm system symbols
BS 5266 — Emergency lighting symbols
Types of Electrical Drawings
| Drawing Type | Focus | Primary User |
|---|---|---|
| Schematic (circuit diagram) | Logical / functional flow | Engineers, troubleshooters |
| Wiring diagram | Physical connections, terminal numbers | Installers, panel builders |
| Architectural layout | Spatial location on floor plan | Electricians, architects |
| Single-line diagram | System overview, simplified paths | Facility managers |
Switches
| Symbol | Name | Notes |
|---|---|---|
| —/— | One-way switch (SPST) | Single pole, single throw |
| —/⟍— | Two-way switch (SPDT) | Used in pairs for staircase lighting |
| —⟍⟋— | Intermediate switch | 4-terminal crossover — between two 2-way switches |
| —/↗— | Dimmer switch | Diagonal arrow = adjustability |
| - - /— | Pull-cord switch | Mandatory in bathroom zones |
Socket Outlets
| Symbol | Name | Notes |
|---|---|---|
| ⌓ | Single socket outlet | Semi-circle = socket face |
| ⌓⌓ | Double (twin) socket outlet | Or single symbol with '2' |
| ⌓ (sw) | Switched socket outlet | Tick or line for integrated switch |
| ▭ — | Fused connection unit (FCU) | Rectangle with fuse line; add switch/neon as needed |
| ⌓ (20A) | 20A double-pole switch outlet | For immersion, water heater |
Luminaires & Lighting
| Symbol | Name | Notes |
|---|---|---|
| ⊗ | General lamp / pendant | Circle with cross |
| ▭ | Fluorescent / LED batten | Long rectangle; multiple tubes = parallel lines |
| ⊗ (E) | Emergency luminaire (self-contained) | Luminaire symbol inside square |
| ○ | Bulkhead fitting | Oval / rounded rectangle — outdoor or IP-rated |
| ⊗ ↓ | Pendant drop | Line showing the drop from ceiling |
Protective Devices
| Symbol | Name | Notes |
|---|---|---|
| ▭ — | Fuse (HBC / BS 88) | Rectangle with centre line |
| ⌐ ◡ | MCB (Miniature Circuit Breaker) | Hook (thermal) + semi-circle (magnetic) |
| ◎ ∿ | RCD (Residual Current Device) | Differential coil over L+N conductors |
| ⌐ ◡ ∿ | RCBO | Combines MCB + RCD symbols |
| ⊣ | Isolator / disconnector | Switch with horizontal bar = safe air gap |
Motors & Starters
| Symbol | Name | Notes |
|---|---|---|
| Ⓜ ~ | Single-phase motor | Circle with M + single-phase sine wave |
| Ⓜ 3~ | Three-phase motor | Standard for industrial drives |
| ▭ Y→Δ | Star-delta starter | Rectangle with both winding symbols |
| ▭ / | Contactor | Rectangle with diagonal = operating coil |
| ⌐ ⎍ | Thermal overload relay | Bimetallic hook linked to control contacts |
Earthing & Bonding
| Symbol | Name | Notes |
|---|---|---|
| ⏚ | Earth (general) | Three horizontal lines of decreasing length |
| ⏚ ○ | Protective earth (PE) | Earth symbol in circle — main safety earth |
| ⏛ | Chassis / frame ground | May not be at true earth potential |
| ═ ═ | Equipotential bonding | Parallel lines — all metalwork at same potential |
Fire Alarm (BS 5839)
| Symbol | Name | Notes |
|---|---|---|
| ▫▪ | Manual call point (MCP) | Square with centre square — 'break glass' |
| ○ S | Smoke detector | BS 5839-1 — 7.5 m coverage radius |
| ○ H | Heat detector | BS 5839-1 — 5.3 m coverage radius |
| △ | Alarm sounder / bell | Audible warning device |
| ▭ FACP | Fire alarm control panel | System 'brain' — large rectangle |
Emergency Lighting (BS 5266)
| Symbol | Name | Notes |
|---|---|---|
| ● | Maintained fitting | Shaded circle — always on |
| ○ E | Non-maintained fitting | Unshaded — on only when mains fails |
| ▭ 🏃 | Emergency exit sign | Running man — arrow shows escape direction |
Sensors & Controls
| Symbol | Name | Notes |
|---|---|---|
| ○ PIR | PIR occupancy sensor | Passive infrared — auto lights off when vacant |
| ◁ ← | Photocell (dusk-to-dawn) | Diode with inward arrows — switches on ambient light |
| ○ t | Time switch | Clock face or 't' in circle — programmable timer |
| ○ T | Thermostat | Controls heating/cooling by temperature |
Common Symbol Confusions
MCB vs Wall Switch
An MCB symbol must include the thermal (hook) and magnetic (semi-circle) indicators. Without them, the drawing only shows a manual switch — no overcurrent protection.
RCD vs RCBO
An RCD symbol only shows the differential coil — it provides earth leakage protection but not overload protection. If installed alone, an upstream MCB is needed. An RCBO includes both differential and thermal/magnetic trip indicators.
Dot vs Jump at Crossovers
In modern CAD drawings, crossing lines are not connected unless a dot (junction node) is present. Best practice: avoid four-way junctions — use T-junctions instead.
Key Points
- - BS 7671 Section 514 requires every circuit to be identifiable for inspection and repair
- - Mixed old/new colours require a Reg 514.14.1 caution notice at the distribution board
- - Circuit charts must list: circuit ref, description, protective device, cable spec, and installation method
- - Alphanumeric circuit coding: 1L1 = Distribution Board 1, Phase 1 (Line 1)