Unit 2: Electrical Wiring Components

1. Wiring Materials and Types

Electrical wiring requires materials that can safely conduct electricity and materials that can safely contain it.

Conductors

Materials that allow easy flow of electric current. The most common are:

• Copper: The most widely used conductor. It has excellent conductivity, is ductile (can be drawn into wires), and has good tensile strength.
• Aluminum: Lighter and cheaper than copper. It's a good conductor, but not as good as copper. Its main use is in high-voltage overhead power transmission lines where weight is a major factor.

Insulators

Materials that resist the flow of electric current. They are used to cover conductors for safety.

• PVC (Polyvinyl Chloride): The most common insulator for household wiring. It's cheap, flexible, and provides good insulation.
• Rubber: Used in flexible cables for tools, but less common in fixed wiring now.
• Porcelain: A ceramic material. It's an excellent insulator, very hard, and resistant to heat. Used in high-voltage overhead line insulators and in fuse holders.

2. Conductors and Cables

• Conductor: A single, uninsulated piece of conductive material (e.g., a bare copper wire).
• Wire: A single conductor that is insulated.
• Cable: An assembly of one or more insulated wires, typically enclosed in an outer protective sheath.
  • Example: A "3-core" cable has three insulated wires (e.g., Live, Neutral, Earth) all bundled inside one tough outer jacket.

3. Basics of Wiring: Star and Delta Connection

These terms refer to the way 3-phase electrical power systems are connected (e.g., in transformers or large motors).

Star (Y) Connection

• How it's made: The ends of the three phases (windings) are connected to a single common point, called the Neutral.
• Output: This system provides 4 wires (Phase 1, Phase 2, Phase 3, and Neutral).
• Advantage: It provides two different voltages:
  • Phase Voltage (V_ph): Voltage between one phase and the neutral (e.g., 230V).
  • Line Voltage (V_L): Voltage between any two phases (e.g., 400V). V_L = √3 × V_ph.
• Use: Used in power distribution to buildings, as it provides both 230V (for lights/plugs) and 400V (for heavy machinery).

Delta (Δ) Connection

• How it's made: The three phases are connected in a loop, end-to-end (like a triangle).
• Output: This system typically provides 3 wires (no neutral).
• Property: The Line Voltage is equal to the Phase Voltage (V_L = V_ph).
• Use: Common in high-voltage power transmission and for large industrial motors.

[Image of Star (Y) vs Delta (Δ) wiring diagrams]

4. Wiring Accessories

These are the components used to control and access the electrical wiring system.

• Switches: Used to interrupt (break) or complete (make) a circuit.
  • 1-Way Switch: Simple ON/OFF switch. Controls one light from one location.
  • 2-Way Switch: Has three terminals. Used in pairs to control one light from *two* different locations (e.g., top and bottom of a staircase).
  • Intermediate Switch: Has four terminals. Used *between* two 2-way switches to control a light from three or more locations.
[Image of 2-way switch wiring diagram for a staircase]
• Holder (Lampholder): The socket that a light bulb screws or bayonets into.
• Ceiling Rose: A small enclosure on the ceiling. It acts as a junction box, connecting the fixed wiring in the ceiling to the flexible cord (pendant) of a light fitting.
• Socket Plug: A pair. The socket is the outlet on the wall, and the plug is attached to the appliance's cord. Allows for non-permanent connection to the power supply.
• Main Switch: A large switch, usually located where the power enters the building (at the distribution board or "fuse box"). It can disconnect the power to the *entire* installation at once.

5. Wiring Types (Casing-Capping, Conduit)

Casing-Capping Wiring

A wiring system where insulated wires are run inside a rectangular PVC or wooden channel (the "casing"). A flat strip (the "capping") is used to cover it.

• Advantages:
  • Very cheap and simple to install.
  • Easy to inspect for faults and add new wires.
• Disadvantages:
  • Not mechanically strong; easily damaged.
  • Looks unappealing.
  • Not suitable for damp (wet) areas.
  • Can be a fire risk if the casing is wooden or poor-quality PVC.

Conduit Wiring

A wiring system where insulated wires are drawn through pipes, called "conduits". The conduits can be PVC or metal.

• Surface Conduit: The conduit pipes are mounted on the surface of the walls and ceilings.
• Advantages:
  • Provides excellent mechanical protection for the wires.
  • Very safe from fire risk and moisture (if sealed).
  • Long lifespan.
• Disadvantages:
  • More expensive than casing-capping.
  • Installation is more complex and time-consuming.
  • Can look industrial or unappealing in a home.

Concealed Wiring

This is a type of conduit wiring where the conduit pipes are hidden *inside* the walls, floors, and ceilings. The walls are chased (grooves are cut), the pipes are installed, and then they are covered with plaster.

• Advantages:
  • The best aesthetic appearance; the wiring is invisible.
  • Extremely safe and protected from damage.
• Disadvantages:
  • The most expensive wiring system.
  • Installation is very complex and must be done during building construction.
  • Finding faults, making repairs, or adding new circuits is extremely difficult and costly.