MCB miniature circuit breaker electrical symbol BS EN 60617 — what it represents, where it appears in UK electrical drawings, and how it relates to the rest of the symbol library.
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A Miniature Circuit Breaker to BS EN 60898. Protects against overload and short-circuit fault current. Types B, C and D differentiate by magnetic trip characteristic.
Used in: Every domestic + commercial final circuit; standard protection device on distribution boards.
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A Miniature Circuit Breaker to BS EN 60898. Protects against overload and short-circuit fault current. Types B, C and D differentiate by magnetic trip characteristic.
Every domestic + commercial final circuit; standard protection device on distribution boards.
For the full set of distribution symbols, see the Distribution Symbols reference page — covering every related symbol with the same level of installation context.
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Start free trialOther distribution symbols you may need on the same drawing:
A domestic consumer unit (fuseboard) to BS EN 61439-3. Houses the main switch, RCD/RCBO/MCB protective devices, and (since 2018) SPD and AFDD where required.
Used in: Domestic origin of the installation — typically meter cupboard, under-stairs, garage or hallway.
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A three-phase or single-phase distribution board to BS EN 61439-3 (commercial). Holds MCBs, RCBOs and MCCBs serving final circuits in commercial and industrial buildings.
Used in: Commercial buildings, offices, schools, retail; one per floor or department typically.
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A distribution board fed by a sub-main from the main switchboard. Sub-divides the installation into manageable zones; reduces voltage drop on long runs.
Used in: Large buildings, multi-tenant offices, plant rooms, lift motor rooms, sub-zones.
See all distribution board symbols →A Miniature Circuit Breaker to BS EN 60898. Protects against overload and short-circuit fault current. Types B, C and D differentiate by magnetic trip characteristic.
Used in: Every domestic + commercial final circuit; standard protection device on distribution boards.
See all distribution board symbols →
A Moulded Case Circuit Breaker to BS EN 60947-2. Higher current ratings (typically 100-1600 A) and higher breaking capacity than MCBs. Used as main incomers or for large feeders.
Used in: Main switchgear, sub-main feeders, large motor circuits, three-phase distribution.
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A Residual Current Device to BS EN 61008. Detects imbalance between live and neutral (earth-fault leakage) and trips. 30 mA RCDs provide additional protection against electric shock.
Used in: Bathrooms, kitchens, outdoor sockets, EV chargers — anywhere BS 7671 requires additional protection.
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A Residual Current Breaker with Overcurrent protection to BS EN 61009. Combines RCD + MCB in one device. Each circuit has individual earth fault and overload protection.
Used in: Modern consumer units — preferred to split-load RCD arrangements; one trip = one circuit affected only.
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A Surge Protective Device to BS EN 61643-11. Type 1 (lightning current), Type 2 (transient overvoltage), Type 3 (point of use). BS 7671 443.4 risk assessment usually requires Type 2 at origin.
Used in: New installations + rewires — Type 2 at consumer unit origin; Type 1 where lightning protection is fitted.
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An electromagnetically-operated switch for high-current loads. Coil energised = contacts close. Used to control motors, heating, lighting circuits and timed loads remotely.
Used in: Immersion heaters with off-peak timer, motor starters, large lighting banks, HVAC plant.
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A main switch-disconnector at the origin of the installation. Disconnects all live conductors (including neutral on TT/IT) and must be lockable in OFF position.
Used in: Origin of every installation — domestic consumer unit, commercial main switchboard.
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The utility electricity meter — point of supply, owned by the meter operator. Modern smart meters communicate consumption to the supplier automatically.
Used in: Meter cupboard, garage external wall, riser cupboard; the boundary of utility responsibility.
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A switch that transfers a load between two sources (typically mains and generator). Manual or automatic (ATS). Always break-before-make to prevent backfeeding the grid.
Used in: Standby generators, UPS bypass, dual-supply critical loads, farms, remote homes.
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An Automatic Transfer Switch that detects mains failure and switches to a standby generator without manual intervention. Synchronised return-to-mains when supply restored.
Used in: Hospitals, data centres, telecoms, agricultural sites with standby plant.
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A metal enclosure containing busbars to interconnect multiple sub-main cables — typically at the main switchboard. Allows tap-offs to feed distribution boards without joint boxes.
Used in: Main switchboards, riser shafts, multi-tenant feeder distribution.
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