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House Wiring

Materials for wiring interior electrical systems in buildings vary depending on:

• Intended use and amount of power demand on the circuit • Type of occupancy and size of the building • National and local regulations • Environment in which the wiring must operate.

Wiring systems in a single family home or duplex, for example, are simple, with relatively low power requirements, infrequent changes to the building structure and layout, usually with dry, moderate temperature, and noncorrosive environmental conditions. In a light commercial environment, more frequent wiring changes can be expected, large apparatus may be installed, and special conditions of heat or moisture may apply. Heavy industries have more demanding wiring requirements, such as very large currents and higher voltages, frequent changes of equipment layout, corrosive, or wet or explosive atmospheres

Types of Wiring

There are three main types of circuits encountered in a domestic situation. They are 1. ring circuits, 2. radial circuits 3. lighting circuits. 4. two way circuit

  BIT  

Ring Circuit

Most modern socket circuits are ring circuits or ring mains as they are sometimes referred to. A cable leaves the consumer unit and travels to each socket on the main and when it reaches the last socket it then returns to the consumer unit, thus creating a ring. The advantage of this system is that power can reach the sockets in the circuit from both directions, which reduces the power load on the cables.

A ring circuit can serve an area up to 110 square metres (120 square yards), 2.5mm2 cable is used to wire the circuit and the circuit has a 30amp fuse or 32amp MCB on the consumer unit. It is usual for a house to have one ring circuit upstairs and one ring circuit downstairs.

Ring circuits can have extra sockets added to them by adding a 'spur' onto a ring circuit. A spur is a branch off the ring circuit, usually from an existing circuit, although a junction box could also be used. Theoretically as many spurs as sockets could be added, but the maximum load of the circuit (30/32amp) still exists).

  BIT  

Lighting Circuit

Lighting circuits are basically radial circuits. There are two distinct types of lighting, circuit the loop-in circuit and the older junction box circuit. Most houses combine aspects of both types of circuits. The loop-in circuit has a cable, running from light to light terminating at the last light as in the conventional radial circuits and then single cable run from the lights to the light switches.

The other type of lighting circuit has a junction box for each light. The cable runs from the consumer unit to the first junction box and then onto the next terminating at the last junction box. Then another cable is run from each junction box to its light and another wire from the junction box to that light switch. The cable used for a lighting circuit is 1mm2 or 1.5mm2 for long runs.

A 5amp fuse or 6amp MCB is used on the consumer unit for a lighting circuit. The maximum load for a lighting circuit is 1200 watts, which amounts to 12 x 100 watt lights. If more lights are needed then another lighting circuit should be used. It is usual to have 2 lighting circuits in a house one upstairs and the other downstairs.

  BIT  

Two Way Switch

A two way switch has to work in pairs. A two way switch has three terminals, as seen in the diagram, S1 and S2 represents the two switches. In S1 is the live wire goes to a and then connected to c in the switch. In this case, the b terminal and the c terminal are the common terminals connected by two common wires to the common terminals of S2.

The diagram demonstrate a state where the light are now being switched OFF. for example, S1 is installed at one end of the corridor and S2 at the far end. When you enter the corridor, you will switch on the lights using S1. Inside the S1, the terminals are closed a and c. when you toggle the switch is the copper strip connecting a and c will be pushed to connect to b. That means a and b now forms a closed circuit.

The live wire from the mains go to a connected to c where it is again connected by common wire 2 to b2 of S2 which is the switch at the end of the corridor. This live supply then passes through to b2 to a2 and onwards to the light, thus completing the full loop to light up the light. All this while, S2 has never been touched.

When you walk right to the end of the corridor and you want to switch OFF the light, the switch will toggle the terminal from b2 to c2, breaking the circuit, thereby switching OFF the lights. The switch will stay that way for the whole duration until someone else switches the lights ON again at either end. When that happens the reverse order happens.

  BIT  

Electrical cables

In a wire the metal (usually copper) has been drawn into a very long, thin thread or rod. Cable is bundle of insulated wires through which at least a single signal. In the cable the individual wires inside the cable are insulated usingsome suitable insulation material (also called dielectric). Typical insulation materials are rubber and plastic, but there arealso other possibilities (air, vacuum, paper etc.). The insulation material used and the thickness of insulation of determine the cable capacitance and what voltages the the insulation can withstand.

• Two-core-and-earth cable (also called twin-and-earth), a bare earth core is sandwiched between a sheathed live (brown) and neutral (blue) wire. • Three-core-and-earth cable a bare earth core lies with three sheathed wires, any or all of which can be live, in brown, black and grey. These cables are used for two-way lighting circuits, where a light fitting is controlled by two switches, for example at the top and bottom of a staircase. • Single core cable is most often used in industrial applications, but may be required domestically for earth bonding. In the case of earthing wire, this is a single wire, surrounded by yellow and green insulating plastic.

  BIT  

In our work site Hedges Court we use some dimensions to fix the sockets and switches, wall brackets,sever sockets, bells, ac sockets.

• Switches box-350mm from 1000mm level

• Wall brackets-1290mm from 1000mm level

• Socket box-740mm from 1000mm level

• Ac socket-1500mm from 1000mm level

• Bell-850mm from 1000mm level

After finishing a wiring we check if the circuit are correct or in-correct. We check it by: • Light testing • Megger testing

Megger

Megger is an electrical equipment which is use to measure high resistance which beyond the range of normal resistance. Mainly it uses for measure the resistance of the generator alternators,the coil of motors.we can expected by using this instruments to check insulation quality of the wiring. If damage the insulation it shows by the megger. We give 200mega ohms to check wiring.

  BIT  

Switch & socket box

Switches

Sever socket

  BIT  

Inspection and Testing

Chapter 6 of and IEE regulation require that “Every installation shall on completiton and before being enirgised. Be inspected and tested in accordance with the requirements.” The method of test shall be much that be danger to persons or property or danger to equipments can occure even it the circuit in defective.

Visual Inspection

Visual inspection also includes inspections by touch or feel and ensure that the materials and the equipments should conform to the British standerd or equirate. Visual inspection will also ensure that the equipment is selected in accordance wiyh the regulations and futher that there is no visible damage which may impair safety.

A check list of items to be examined under visual inspection as relavant to domestic wiring • Connection of contudes • Identification of conductors • Selection of conductors for current carrying capacity and voltage drop. • Connection of single pole devices for protection or switching in phase conductors only. • Correct connection of socket outlets and lamps. • Presences of appropriate devices for isolation and switching • Labeling of circuit, fuses, switches, terminals. • Selection of equipment and protective measures

Testing • Continuity of ring final cct conductors • Continuity of protective conductors   BIT  

• Measurements of earth electrode resistance. • Insulation resistance • Operation of ELCB

  BIT