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

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