Page 88 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Wiring system

Wiring: A network of wires connecting various accessories for distribution of electrical energy from the supplier
meter board to the numerous consuming devices through controlling and safety devices.
Systems of distribution of electrical energy: Since as per recommendation of Indian Standard the maximum
number of lights, fans and 5A socket outlets that can be connected in one circuit is 10 and the maximum load that
can be connected in such a circuits 800W, in case more load or points are required to be connected to the supply,
then it is to be done by having more than one circuit. There are two systems are used for distribution of electrical
energy in more than one circuit
1 Tree system

2 Distribution board system
1 Tree system
In this system small branches are taken from the main branch as shown in fig.

And the wiring system resembles a tree, as each branch is taken off, a fuse is inserted.
This system used to be employed in early days. Now a day it is no more adopted due to the following draw backs.

Dis advantages
• The voltage across all lamps does not remain same, lamp in the last branch will have least voltage across
them on account of voltage drop in leads.

• A number of joints are involved in every circuit.
• Fuses are scattered
• In case occurrence of fault all the joints have to be located and if some of these joints are concealed floor or
roofs space, a lot of difficult are faced.
2 Distribution board system: Which is most commonly adopted system for distribution of electrical energy in a
building. The fuses of various circuits are grouped together on distribution board.the two copper strips called
Bus bars are connected to the supply mains through a DP switch, so switched off whole circuit, if required. A
fuse is inserted in phase pole of each circuit, so that each circuit is connected up through its own particular
fuse. The distribution board shown in fig. has 4 ways for 4 circuit but no limit to the no. of ways or circuit,
provided the cable feeding, the board is large enough to carry the total current.

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CITS : Power - Electrician & Wireman - Lesson 20-25