Cable Trunking

To put cables in such trunking one normally takes the lid off , lays the cables in and replacs the lid , but it is possible over short distances or straight length to pull the cables in as one does with conduit . WHichever method is adopted , the number of cables and sizes of trunking must be such that no damage is caused during installation ,. The same considerations apply as in the case of conduit .
  Being so mucj larger than conduit , trunking can quiete clearly not be buried in the walls of a building . It has to be run on a surface . THere are occasions when there are other services such as heatingm pipes or gas . THis is one situation in which cable trunking is an ideal way of installing the wiring . It can be similarly used in false ceilings . In both these cases , there must be sufficient doors or access traps to enable electricians to reach the trunking for rewiring .
  Buildings such as assembly halls and gyms often hae exposed steel lattice framework supporting the roof . It is then possible to run cables trunking neatly through the spaces of  the lattice . Sometimes the architect will permit the cable trunkiing to be fixed under the beams and along them . Either method is simpler and neater than fixing several conduits parallel to each other on the surface of the ceiling , and has the further advantage that during the life of the building , the wiring can be altered very easily . Lighting trunking has additional folds in the cross setion which makes it more rigid than conventional trunking and is able to span greater distances .
  In workshops and laboratories there is usually a large number of machines and other equipment which have to be served with electricity , A conduit system can then becoe complex and , therefore , expensive . A simple and neat method of wiring these areas is to run trunkin round the walls and to install all the circuits inside the trunking  . In rooms of this class , this is quite acceptable and no one objects to the appearance of trunking visible on walls . Again there is the advantage that when machines are replaced or when new machines are installed , the consequent changes to the elctrical service are easily made . The same consideration applies  , but with added force , to factories .
    When machines are place in the centre of a room a good method or serving them is to run trunking at high level under the ceiling and drop to each nmachine with a length of conduit , It is , of course , possible to install conduit withint he floor with an outlet near each machine , but there then has to be either rigid or flexible conduit at floor level , and if machines are moved or additional ones brought in the floor has to be dug up before the conduit can be extended to the new position . For the initial installation the elctrician would have to known the exact positin of the terminals of each machine before the floor is laid , and it is very seldom that either the buildier or the final occupier of the factory can provide this infdormation so early . THe overhead system avoids the difficulty of locating exact position of machines too early in the construction process and makes future changes more easy .

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