Page 94 - Electrician - TT (Volume 1)
P. 94

ELECTRICIAN - CITS





           5  Good mechanical protection.
           6  Very good appearance.
           Disadvantages
           1  Good workmanship is required.

           2  It is not used under the situations open to sun and rain.
           Application
           1  Used for lighting purposes in domestic, commercial or industrial buildings except in workshops where it is
              liable to mechanical injury.
           Lead sheathed wiring system
           1  It is used for low voltage installation.
           2  It is not suitable where acids and alkalies are present
           3  Single, two and three core lead covered VIR cables are used
           4  The cables are fixed to the wooden batten (thickness more than 10 mm) by means of nails and joint clips or
              link clips
           5  Clip distance for horizontal run-10.cm,for vertical run -15.cm
           6  The wooden battens are fixed on the wall by means of wooden screws at a distance of minimum 60.cm and
              max.   75. cm
           7  When lead sheathed wiring system pass through a floor or a wall, the cable must  pass through conduits
           8  The bending radius of these cable should be not less than 10.cm
           9  The lead sheath should always be electrically continuous and properly earthed.
           Advantages
           1  There is sufficient mechanical protection to the cable due to the lead sheathing on the cable
           2  Protection from fire is also good

           3  This system provides good protection from dampness if the ends of the cables are properly sealed
           Disadvantages
           1  Expensive
           2  Lead sheath of the cable can be damaged due to the bad workmanship

           3  Not suitable where fumes  and acids are present
           Application
           1  It is used in low voltage installation.
           2  It is used in damp places with protective covering.
           3  It is not used in places where chemical corrosion may occur.
           Conduit wiring

           Types
           Surface conduit (PVC &Metal) Done on wall surfaces
           Concealed conduit (PVC)Done inside concrete plaster or wall
           Types of conduit

           1  Rigid steel conduit
           2  Rigid non-metallic conduit
           3  Flexible steel conduit
           4  Non -metallic conduit



                                                           81

 CITS : Power - Electrician & Wireman - Lesson 20-25  CITS : Power - Electrician & Wireman - Lesson 20-25
   89   90   91   92   93   94   95   96   97   98   99