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Electrical Supply and Earth Continuity

Exam revision materials for Plumbing Level 2&3 and ACS Gas Safety test

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Fuse Types

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Electrical tests

Testing Equipment

Types of Electrical Tests

Central Heating Wiring Diagrams

Central Heating Diagrams

Electrical Current

Types of Electrical Systems


Fuse Types

Safety Requirements

Wires and Cables

Cable Protection

Cable Sizing

Cable Types

Electrical Circuits

Electrical Bathroom Zones

Electrical Components

Electrical Fittings

Switches and Sockets


Earth Bonding

Earth Bonding

Cartridge Fuse

  • Usually found in plugs
  • 45A >13kW
  • 30A > 7kW
  • 20A – for storage and water heater circuits
  • 15A < 3kw for single appliances circuit
  • 13A between 700W – 3kW
  • 5A for lighting circuit (MAX load is 1200W or 12x100W lamps)
  • 3A < 700W (table lamps and alarm clock)
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High Breaking/Rupture Capacity Fuse (HBC)

  • link can blow without the fuse itself being destroyed
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Miniature Circuit Breaker (MCB)

  • opening as a result of the increased heat or magnetism
  • Situated in the Consumer Unit
  • Trips out when fault occurs
  • Protects against overload
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Residual Current Device (RCD)

  • senses an imbalance of current between the phase and neutral
  • Protects against Earth faults
  • Operate when detecting the fault above 30mA
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Residual Current Breaker with Overload (RCBO)

  • Combination of MCB and RCD
  • Recommended for commercial installations
  • Protects single circuits (ring with lots of computers in use)
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Rewireable Fuse

  • Not used on new installations because wrong wire can be used
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Suppliers Main Service Fuse

  • supplier’s cut out
  • part of the Supply Company’s Head
  • Sealed and can be served only by electricity supplier
  • MIN 750mm below roads (MIN 450 if below open grounds) – underground supply cables
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Customers Consumer Unit (CCU)

  • 25mm2 – cross sectional area cable between Company’s Head and CCU for live and neutral
  • Contains the main double-pole switch
  • Bus bar?????????????
  • Circuit Protection Conductors (CPC) – where “earth” conductors are terminated (Earthing Bar)
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Main Earth Terminal

  • 16mm2 earthing conductor from earthing bar in CCU
  • 16mm2 cable to the service head or outer casing of the supply cable  - in case of underground supply
  • To an earth electrode (main earthing conductor) – in case of overhead supply
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