Electrical System In Building
The purpose of the electrical system in building is to distribute the power safely to all of the different rooms and appliances.The electrician at first places all of the boxes for electrical outlets, lights and switches.
House Wiring Rules and Electrical System In Building
All materials used for house.-wiring i.e., wires and accessories should be of good quality, preferably having Bureau of Indian Standard (BIS) Mark.
The number of points in a light circuit is not to exceed 10.
The switch board is to be fitted at a height of 1.5 metres.
The horizontal run of the wiring on walls should be at a height of 3 metres.
Use only three pin sockets.
The minimum, size of earth wire is.4 square millimeters for aluminium.
The fuse wire should be connected to the phase wire only.
Connect all switches in the phase wire only.
Power Circuit shall have maximum 2 points.
Colours of Insulation for Wires
Phase wire: red, yellow & blue
Neutral wire: black
Earth wire : green
Copper wires are more corrosion resistant and are more flexible for bending compared to Aluminum wires but are costlier than Aluminum.
Notes on Earthing
Earthing is of two types;
G.l Pipe or plate electrode is normally used. Where soil conditions are corrosive, copper pipe or copper plate electrode is used for earthing. The location of earth pit should be such where the soil has a reasonable chance of remaining moist. Entrances, pavements and roadway are definitely avoided for locating earth pits.
Dry earth has more resistance while moist earth has less resistance. Charcoal and salt decrease the resistance of earth, That is why they are filled in earth pit.
A masonry enclosure is normally made over earth pit for watering arrangement. A funnel on the top of pipe at ground level inside a masonry chamber is used to put water frequently for decreasing earth resistance.
Galvanized iron earth wire from the main Distribution Board is connected to Gl or Copper earth pipe at earthing pit through bolt & nut for earthing purpose.Inside the building, in addition to all the electrical appliances, all switch boxes,metre box etc., should also be earthed. For checking the earth connection at 3 pin socket and other places, connect leads of test lamp between phase and earth.If the bulb glows, the earth connection is alright.
Defects in Electrical Circuits
Open Circuit Fault: The current flows in a closed circuit. Therefore, continuity must be present. Whenever there is a break in the circuit, the current does not flow. This is called open circuit fault. This fault is caused due to burnt out element, broken wire, loose/open connection, a corroded or rusted point.
Short Circuit: It is a condition in which the supply is connected to live and neutral wire without a load. in such a situation, the fuse blows out. It is caused due to insulation failure and loose connection.
Human Body is a conductor, When the live wire touches the body, the current flows through the body and the muscular functions of the body are paralysed. When the body is dry, its resistance is more hence less current for the same voltage and hence less shock. Similarly, when the body is wet, its resistance is less, so more current for the same voltage and more shock.
In A C supply system the earthing of electrical equipment is necessary to avoid shocks and earth leakage for safety of human beings and fires. In our present system, though there is provision of earthing, sufficient care is not taken to maintain a proper earthing and to connect all electrical gadgets to earth wire.In most of the cases, the earth wire is ignored.
Types of Lighting Fixtures
General Lighting Service Lamp: Used inside houses
Sodium Vapour Lamp: Normally used for Street Lighting
Mercury Vapour Lamp: Normally used for Street lighting
Halogen Lamp:Flood light
Florescent Tube Light(FTL) : available in length of Il.to 5 feet.
Compact Florescent Lamp(CFL): Cost effective lighting inside houses
Regarding fittings, plugs, sockets, switches, the quality of these products plays an important role. invariably small sparks start from these fittings due to poor quality and workmanship and even though the sparks are of small intensity they are liable to ignite inflammable materials in the vicinity.
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