conduit fixings

  Electrical conduit is to thick enough to support its own weight over long distances without sagging . The support must , therefore , be at quite close intervals , and the maximum distance which should be allowed between supports are as follows :
 20mm conduit  -horizontal support (1.75m ) - vertical support (2.0m )
25 and 32mm conduit - horizontal support ( 2.0m )- vertical support 2.5m
40mm and over  - horizontal support (2.25m ) -vertical support (2.5m)

The IEE Guidance Note 1 and the IEE On-Site Guide both give guidance on the maximum spacing of conduit fastenings .
  The cables are drawn into the conduit with the help of a steel tape and a draw cable . The steel tape has a hemispherical brass cap on the end which prevents its sticking on irregularities at joints of the conduit and also helps guide it round bends  THe tape also has a loop at its other end and a steel draw cable is attached to this . The cables themselves are then attached to the other end of the draw cable . The electrician attaches  the cables by threading them through a series of loops in the draw cable . THey should not all be attached to the same point otherwise there is a significant . sudden enlargement in the bunch of cables and this presents and edge whch can catch in the bore of the conduit and which will be difficult to negotiate bends . When each cable is looped through the draw cable , it is folded back on itself and the end is taped . This gives a smooth surface to sticking out and catching the insid of the conduit . THe method of connection is shown in Fiogure 3.11 .
  Pulling cables through conduit is a job for electrician and mate. One pushes the steel tape with the draw cable attached to it from one draw-in box to the next : as soon as the tape appears at the receiving boc , the other takes it and pulls gently from that end . The lattter then pulls the draw cable and finally the bunch of cables while the former feeds them into the conduit . The person feeding the cables in must do so carefully and must guide the cables so that they do not cross or twist over each other as they enter the conduit . IF they are allowed to twist , the whole bunch may stick nd even if they can be forced in , it may be impossible to withdraw some of them later . The whole bunch may stick and even if they can be forced in , it may be impossible to withdraw some of them later . The whole job require great care and needs cooperation between the two people at opposite ends of the run . It is a help if they are within sight of each other and essential that they should be within earshot of each other . On the rare occasions when the run of conduit through the building from one draw in box to the next makes it impossible for shouted directions to be heard from one end to the other , a thrid person will have to be called in to stand halfway and relay messages , or use an intercom .
  In hot weather , the insulation of the cables is liable to become soft and tacky . Drawing it through the conduit may be made easier by rubing French chalk on the cables . In other circumstances , when friction between the cables and the conduit is high and makes pulling in difficult , it may be advantageous to apply him a thin coating of grease or tallow wax to the cables .


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