to the 16th Edition IEE Regulations
   
   
   
 
 

chapter 5
Earthing

chapter 6
Circuits

Cables, conduits and trunking
  4.1 - Cable insulation materials 4.4 - Cable supports, joints and terminations
  4.2 - Cables 4.5 - Cable enclosures
  4.3 - Cable choice 4.6 - Conductor and cable identification
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4.2.3 - Flexible low voltage cables and cords

By definition flexible cables have conductors of cross-sectional area 4 mm or greater, whilst flexible cords are sized at 4 mm or smaller. Quite clearly, the electrician is nearly always concerned with flexible cords rather than flexible cables.

{Figure 4.2} shows some of the many types of flexible cords which are available.


a) Braided circular - Fig 4.2a

1 - oversheath - PVC 4 - insulation - pvc coloured
2 - braid - plain copper wire 5 - Conductors - plain Copper
3 - inner sheath - pvc  


b) Unkinkable - Fig 4.2b

1 -rubber layer collectively textile braided semi-embedded
2 - insulation (Cores) 60C rubber
3 -conductors - tinned copper


c)Circular sheathed - Fig 4.2c

1 - sheath - rubber or pvc
2 - insulation 60C rubber or pvc
3 - conductors - tinned copper


d)Flat twin sheathed - Fig 4.2d

1 - sheath - PVC
2 - insulation - pvc
3 - conductors - plain copper


e) Braided circular insulated with glass fibre - Fig 4.2e

1 - glass braided overall
2 - insulation - silicon rubber
3 - conductors - stranded Copper


f) Single core p.v.c. - insulated non-sheathed - Fig 4.2f

1 - insulation - pvc
2 - conductors - plain copper

Flexible cables should not normally be used for fixed wiring, but if they are, they must be visible throughout their length. The maximum mass which can be supported by each flexible cord is listed in (Table 4H3A), part of which is shown here as (Table 4.2).

Table 4.2 - Maximum mass supported by twin flexible cord
Cross-sectional area (mm)
Maximum mass to be supported (kg)
0.5
2
0.75
3
1.0
5
1.25
5
1.5
5

The temperature at the cord entry to luminaires is often very high, especially where filament lamps are used. It is important that the cable or flexible cord used for final entry is of a suitable heat resisting type, such as 150C rubber- insulated and braided. (Fig 4.3) shows a short length of such cord used to make the final connection to a luminaire.

Fig 4.3 - 150°C rubber-insulated and braided flexible cord used
for the final connection to a luminaire

 

 

 

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Extracted from The Electricians Guide Fifth Edition
by John Whitfield
Published by EPA Press Click Here to order your Copy

Click here for list of abbreviations