A common challenge many professionals face is selecting the appropriate conduit size for housing electrical wires, ensuring both safety and efficient functionality. In this guide, we’ll break down the step-by-step process to determine the correct conduit size in line with CEC standards.
Identify the Conductors
The first step is understanding the types, sizes, and the number of conductors you’re planning to run through the conduit.
Determine the Total Cross-Sectional Area (Table 10A/10B):
Every conductor size and type has a defined cross-sectional area. Using the CEC tables, find the area for each conductor and multiply by the number of that type and size. Sum up the total areas to get the combined cross-sectional area.
Fill Percentage (Table 8):
CEC has specific fill percentage requirements based on the number of conductors in a conduit, so choose the right percentage based on your number of conductors.
Calculate Conduit Size:
To determine the required conduit size, divide the combined cross-sectional area of the conductors by the appropriate fill percentage. This will give you the minimum conduit area required.
For example, if your combined wire area is 200 mm² and you have more than two wires, you’d calculate:
200 mm² ÷ 0.40 = 500 mm²
This means you would need a conduit that has an internal area of at least 500 mm².
Select the Right Conduit (Tables 9A to 9P):
Once you have the minimum area required, refer to the CEC tables to find the conduit types and sizes that meet or exceed this area. It’s typically best to choose a size that’s a little larger than the minimum to account for potential future additions or changes.
Apart from fill percentage, remember to account for other factors like the conduit material (PVC, metal, etc.), ambient temperature, number of bends, and conduit length which might affect wire pulling tension.
Correct conduit sizing is a crucial aspect of electrical installations, ensuring safety, functionality, and code compliance. Always refer to the most recent edition of the CEC for updated guidelines and detailed tables to help with your calculations.