Page 92 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

14 The switches and starters of motors should be easily accessible to the apparatus.
15 Water proof light fittings should be used for outdoor lightings.
Mounting level of the accessories and cables
• Height of the main and branch distribution board should be not more than 2 meter from the floor level.
• Front clearance of one meter should also provided

• Switch shall be installed at any height 1.3 meter above the floor level.
• All the light fittings shall be at a height of not less than 2.25 meter from the floor.
• Socket outlets shall be installed either .25 or 1.3 meter above the floor as desired.
• No socket out let’s shall be provided in bathroom at a height less than 1.3 meter.
• Clearance between the bottom point of ceiling fan and the floor shall be not less than 2.4 meter. Minimum
clearance between the ceiling and the plane of the blades of the fan not less than 30 cm.
• The cable shall be run any desired height from the ground level.
Factors for selection of wiring

• Safety
- The first and foremost consideration is safety to the person using electricity against leakage or shock.
• Durability
- The type of selected wiring must be durable and also in accordance with accessed life and type of building.
• Appearance:

- Wiring must provide a good look after its installing.
• Mechanical protection
- Wiring must be protected from mechanical damage during its use.
Systems of wiring
The types of internal wiring usually employed in our country are

1 Cleat Wiring.
2 Casing and Capping (Wooden/ PVC) Wiring.
3 CTS or TRS or PVC Sheathed Wiring.
4 Lead Sheathed or Metal Sheathed Wiring
5 Conduit Wiring

a Rigid Steel Conduit Wiring.
b Rigid Non Metallic Conduit Wiring.
a Open / Surface Wiring
b Concealed / Recessed / Under Ground Type

CTS or TRS wiring
In this wiring system, single, twin or three core tough rubber sheathed cables are used. TRS cable should not be
exposed to sun and rain.
PVC sheathed cables are used for medium voltage installation. PVC sheathed cables may be installed under the
exposed condition of sun, rain or damp places and where acids and alkalies are present.
TRS cables are fixed on well-seasoned perfectly straight and well varnished wooden battens. TRS cables are
fixed on the batten by means of joint clips. The thickness of batten is 10 to 19 mm and width is 10 to 50 mm
(depends up on total width of the cable .Wooden plugs are used for fixing the batten fixed at an interval not
exceeding 75 cm.

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