Page 96 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

dia- and number of cables. Conduits are fixed on the walls by means of saddles. Spacing between saddles or
supports is 60 cm for rigid non- metallic conduit as per NE code. Rigid PVC conduits are not suitable for the
working temperature of conduits and fitting may exceed 55°c
Fastening cable with draw spring
Wires are drawn through the conduits by means of draw spring

Cold bending of pvc pipe (by using bending spring)

PVC conduit, not exceeding 25.mm diameter can be bend cold by using bending spring
Comparison between metal and pvc conduit wirings
Sl. No: Metal conduit PVC conduit
1 Provides good physical protection to cables Comparatively poor

2 Weighs more for a given length Lighter
3 Needs skill and time for installation Needs less skill and time
4 Risk of electric shock due to leakage No risk as PVC is an insulator
5 Good earth continuity available through Not possible .Separate earth
the pipe itself wire is required
6 Can be used in gas tight and explosive Not suitable
-proof installation.

7 Not resistant to corrosion, needs Resistant to corrosion
protective coating
8 Large ambient temperature range Suitable for limited temperature range
.Above 60°c the conduit starts melting
and very low temperature the conduit
cracks
9 Fire resistant Not fire resistant
10 More costly Less costly

Non metallic conduit accessories
1 Couplers 3 Bents 5 Boxes (Circular boxes and Rectangular boxes)
2 Elbows 4 Tees

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