Page 128 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

So the phase ampere turns exceeds neutral ampere turns and an alternating magnetic flux results in the core.
The flux links with the secondary coil wound on the same magnetic circuit inducing an emf into it. The value of this
emf depends on the residual current, so it drives a current to the tripping system which depends on the difference
between them and neutral current.
When tripping current reaches a predetermined level the circuit breaker trips and open the main contacts and
thus interrupts the circuit.
Types domestic wiring

Objectives: At the end of this lesson you shall be able to:
• state the types wiring used in domestic installations.

Introduction
The type of wiring to be adopted is dependent on various factors viz. location durability, safety, appearance, cost
and consumer’s budget etc.

Types of wiring
The following are the types of internal wiring used in domestic installations.
• Cleat wiring (for temporary wiring only)
• CTS/TRS (batten) wiring

• Metal/PVC conduit wiring, either on surface or concealed in the wall.
• PVC casing & capping wiring
Cleat wiring
This system uses insulated cables supported in porcelain cleats (Fig 1).
Cleat wiring is recommended only for temporary installations. These cleats are made in pairs having bottom and
top halves (Fig 2). Bottom half is grooved to receive the wire and the top half is for cable grip.
Initially the bottom and top cleats are fixed on the wall loosely according to the layout. Then the cable is drawn
through the cleat grooves, and it is tensioned by pulling and the cleats are tightened by the screw.
The cleats are of three types, having one, two or three grooves, so as to receive one, two or three wires.
Cleat wiring is one of the cheapest wirings considering the initial cost and labour, and is most suitable for
temporary wiring. This wiring can be quickly installed, easily inspected and altered. When not required this wiring
could be dismantled without damage to the cables, cleats and accessories. This type of wiring may be done by
semi-skilled persons.

Fig 1 Fig 2

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