How To Turn Off The Main Switch
In these situation one has to be extremely cautious of where to place a hand and always remember that safety should be a priority of one's action. To begin,
Take out the fuse carriers one by one and exermine them. It is easier to find the blown fuse if the fuse carrier and label match the rooms for which they are responsible.
The carriers become blackened after the fuse is blown.
There Are Two Types Of Fuses
1) Rewireable fuse
2) Cartridge fuse or High Breaking Capacity Fuse.
Switch Used For Lighting
1) One way switch with two terminals
2) Two way switch with three terminal 3) Intermediate switch with four terminals.
• Single way switch: This is usually of two terminals, it is usually used to control single way sub-circuit, mostly lighting circuit.
• Two way switch: This is usually of three terminals and is mostly used where circuit can be controlled from two or more different position.
• Intermediate switch: This type consist of four terminals and is normally used for conjunction with two - way switch where a circuit usually lighting point is to be controlled from several position.
• A rotary switch: This type of switch is usually used with heating appliances e.g electric cooker where slow, medium or high switching position may be needed.
• A pull cord type switch: This is mostly used in sleeping rooms or bath rooms where it may be dangerous for the person in contact with water to touch the switch.
Points Of Note When Undertaking electrical wiring
The wiring of any building (either private or public) is to be undertaken, some points should be taken into consideration;
a) Type of installation required
b) Number of points required
c) Materials needed for the job.
Any electrician who undertake the job should be competent and should be able to make a complete lot of the materials needed for the job. e.g cable, p.v.c and flexible cord. Accessories ; this includes switches, lamp holders, ceiling rose, socket outlet and plugs, joint boxes, consumer control unit, Other materials includes wooden block, nails, clips e.t.c when all materials required for the installation are completed, the electrician or the wiring contractor should plan the installation.
Planning should include the laying of cable of reasonable position. Mounting of wooden blocks and the consumer control unit cable should be clipped at equal and correct distance e.g ( 15cm or 6 inches apart). As to afford firmness and good appearance of all cables, installation should be protected against any likely hood of mechanical damage and against sunlight e.g ( T.R cable).
• Termination: Termination at switch points, joint boxes and ceiling rose should be mechanically strong and electrically firm.
Electrically continuous( bending cable) should be perfectly made to give nice appearance.
• Tools: A good electrician should possess a good set of tools for the job, and tools should be correct and also the way he looks after his tools and the condition in which he keeps them is an indication of the quality of job he can produce.
The Supply Authority Responsibility
After the completion of the electrical installation of the building, the supply authority responsibility is to supply electrical energy to the installation via the following items ;
•The supply authority main fuses
• The service cable
• The supply authority metre panel.
Note:
The supply authority should ascertain that the electrical installation has been undertaken by a competent "Government License Electrical Contractor". The supply authority should see that system of installation is effective.
Consumer / Installation
Wiring and apparatus situated upon the consumer premises are controlled by them.
• Consumer Terminals: This is The point in the consumer Installation of which the incoming supply energy is delivered to that installation.
• Dead: At or about earth potential are disconnected from the life system.
• Distribution Board: The assemble of parts including one or more fuses or circuit breakers arrangement for the distributed electrical energy to the final sub - circuit or to other distribution board.
• Earthen: Effectively connected to the general mass of the earth.
• Fuses: A device for opening a circuit.
• Generator: A machine that converts mechanical energy to electrical energy.
• Earth Tester: This is used for testing the earth resistance of an area.
• Voltmeter: Used for reading voltage.
Electrical Measuring Instrument
• A Voltmeter: This is an instrument used for measuring the potential difference between the points in principle consisting of an arrangement similar to a metre with a high resistance in series Incorporated in the instrument. The scale being callorated in volts, it must be connected in parallel with the rest point to the rest part of the circuit between the points.
•Ammeter: This instrument is used for the measurement if electric current. It is always connected in series with other components of the circuit.
•Watt - Meter: It is a device used to measure electrical power consumed in a circuit. Combination of a volt meter and ammeter with a pointer conforms to a watt meter.
Quality Of Electricity
The coulombs: (Amp, or Amp HRS). The unity if electric quantity is the coulombs (symbols) one coulombs is the quantity of electricity converted in a second by a current of one ampere (6.3 × 10^18 electron in one second which is = 6413.4)
Possession Of Distribution Board
Although the main switch will also be connected as well as to the meter position, the location of the distribution board will depend upon the size of the installation for the distribution board to be located centrally to enable all sub - circuit wiring to be kept as soon as possible.
This is mainly an economic method in order to combine the cost of some main cable, feeding the distribution board from the main switch gear against the saving of an additional length if sub-circuit wirings.
Whatever or no matter the size of an installation, the same rate must be followed when deciding details of main switch gears and the distribution of final circuit.
To test mate the maximum load of an intended installation, all current consuming loads are in watts. Having known all these we can now calculate the size of the main switch gear and a suitable size of the distribution board.
Preventive Measures
The Risk Of Shock: A shock arises whenever accidental contact is made between life conductor and exposed metal work. This risk can be guided against either by effective earthing or by putting on a glove.