Calculate Conduit Size for Wires / Cables


Example: Calculate Size of Conduit (Hume Pipe) for Following Size of Cables

  • 5 No’s of 3.5 Core 50 Sq.mm XLPE Cable. Diameter of cable is 28mm
  • 3 No’s of 3.5 Core 185 Sq.mm XLPE Cable. Diameter of cable is 54mm

% Fill Up Area of Conduit

No of Cables % Fill up Area of Conduit
Up to 2 No’s 53%
2 No’s 31%
More Than 2 No’s 40%

Calculations:

  • Area of Cable =3.14 X (Diameter/2)2
  • Area of 50 Cable =3.14X (28/2)2 =615.44 Sq.mm
  • Total Area of 50 Cable=No of Cable X Area of Each Cable
  • Total Area of 50 Cable=5X615.44 =3077.2
  • Area of 185 Cable =3.14X (54/2)2 = 2289 Sq.mm
  • Total Area of 185 Cable=No of Cable X Area of Each Cable
  • Total Area of 185 Cable=3X2289=6867.18
  • Total Area of Conductor= Total Area of 50 Cable+ Total Area of 185 Cable
  • Total Area of Conductor=3077.2+6867.18
  • Total Area of Conductor=9944 Sq.mm
  • Suppose We Select 150mm Diameter Hume Pipe
  • Total area of 150 mm Diameter Hume Pipe =3.14 X (Diameter/2)2 =3.14X(150/2)2.
  • Total area of 150 mm Diameter Hume Pipe=17662 Sq.mm.
  • % Fill up Area of Conduit due to Cables as per above Table is 40%
  • Actual Fill up Area of Hume Pipe =40% X Area of Conduit =40% X 17662
  • Actual Fill up Area of Hume Pipe =7065 Sq.mm
  • Required No of Conduit = Total Area of Cables / Actual Fill up Area of Conduit
  • Required No of Conduit = 9944 / 7065
  • Required No of Conduit= 2 No’s
  • Suppose We Select 3000mm Diameter Hume Pipe
  • Total area of 300 mm Diameter Hume Pipe =3.14 X (Diameter/2)2 =3.14X(300/2)2.
  • Total area of 150 mm Diameter Hume Pipe=70650 Sq.mm.
  • Actual Fill up Area of Hume Pipe =40% X Area of Conduit =40% X 70650
  • Actual Fill up Area of Hume Pipe =28260 Sq.mm
  • Required No of Conduit = Total Area of Cables / Actual Fill up Area of Conduit
  • Required No of Conduit = 9944 / 28260
  • Required No of Conduit= 1 No’s

Results:

  • Either We Select
  • 2 No’s of 150 mm Diameter Conduit /Hume Pipe or
  • 1 No’s 300 mm Diameter Conduit /Hume Pipe
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