requirements for circuits

• what are the components needed for a circuit 


  • Power supply : EMF
  • A load : light bulb
  • Means of transport : cable
  • circuit control : switch
  • Circuit protection : RCD/MCB
• What is the key difference between 'isolator' & 'switch'


  • The isolator disconnects/separates the source of supply
  • switch temporarily disconnects the source of supply
• What does the IET regulations tell us about the electrical equipment and materials that needs to be taken into consideration 


  • temperature
  • the presence of water (IP rating)
  • Corrosion
  • mechanical damage
  • Vibration
  • Exposure to solar radiation
• Make sure mechanical damage from the environment or any sort, is to be kept to a minimal during instillation
• When installing, all the links should be removed so that the cable runs straight and neatly between the clips, fixed at equal distances proving adequate support, that the cable doesn't become damaged from its own weight
• When working on terminations or joints in switches, etc, make sure that its enclosed in an non-ignitable material, which is properly secured and are mechanically and electrically secured (IET regulation 526)
• What is needed when PVC insulated and sheathed cables are concealed behind wall, floors or partitions 


  It must be provided a, box incorporating an earth terminal at each outlet position
• What material doesn't PVC cables react chemically with

  Plaster, as they may be burned
• what are the components needed for a circuit to work


  • Power supply : EMF
  • A load : light bulb
  • Means of transport : cable
  • circuit control : switch
  • Circuit protection : RCD/MCB
• • When connecting circuits into the consumer unit the loads with the highest current rating must be placed next to the main switch
  • All consumer units MUST be constructed from non-flammable material or housed in a non-flammable housing
• What are PVC insulated and sheathed cables suitable for

  Domestic instillation
• What Are PVC/SWA cables preferable for

  suitable for being buried underground, with additional mechanical protection
• What are the characteristics of MI cable

  • Waterproof
  • Heatproof
  • corrosion-protection with some mechanical protection
• the qualities of PVC insulated and sheathed cables makes it the only cable choice for hazardous or high - temperature instillations such as:

  • Oil refineries
  • Chemical works
  • Boiler house
  • Petal pump instillation
• Who has the final choice for wiring systems

  It rests with those designing the instillation and those ordering the work
• Whatever system is employed, good workmanship by skilled or instructed persons and the use of proper materials is essential for compliances with the IET regulations (IET regs 134.1.1).
• Mechanical damage to the cable caused by:

  • impact
  • abrasion
  • penetration
  • compression or tension

  Must be minimised during instillation (IET regs 522.6.1)
• Being fixed using dips incorporating a masonry nail, on what types of walls can cables be fixed to

  • Wood
  • Plastic
  • Birch
• All joints must be accessible for inspection, testing and maintenance when the instillation is completed (IET Regs 526.3) unless designed to be maintenance free