Conduit Sizing Explained: Use Tables 6, 8 & 9

In this video, we break down Conduit Sizing according to the Canadian Electrical Code (CEC) and clearly explain how to properly use:

• Table 6 – Conductor cross-sectional area
• Table 8 – Allowable conduit fill percentages
• Table 9 (especially 9G) – Conduit internal capacity

This lesson walks step-by-step through 8 practical exam-style questions and shows exactly how to extract values from the Codebook and apply them correctly.

⚠️ Disclaimer:
This video is for educational purposes only. Always refer to your official Canadian Electrical Code (CEC) published by CSA for complete and accurate requirements.

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🔎 How to Use Tables 6, 8, and 9 (Step-by-Step Method)

Step 1 – Use Table 6

Find the physical cross-sectional area (mm²) of one conductor based on:
• Conductor size (AWG or kcmil)
• Insulation type (T90, RW90, TW, etc.)
• Stranded or solid

Multiply by number of conductors to get total area.

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Step 2 – Apply Table 8

Determine allowable fill percentage:
• 1 conductor → 53%
• 2 conductors → 31%
• 3 or more conductors → 40%

(Most exam questions use 40%)

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Step 3 – Use Table 9 (usually 9G)

Select the smallest conduit trade size that can accommodate the total conductor area within the allowable fill.

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✅ SOLVED QUESTIONS

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✅ Question 1

15 × No. 6 RW90 XLPE (unjacketed)

Table 6A:
No. 6 RW90 = 38 mm²

38 × 15 = 570 mm²

From Table 9G:
Minimum conduit that accommodates ≥ 570 mm² is:

✅ Trade Size 53

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✅ Question 2

78 trade size EMT
350 kcmil R90 XLPE

Table 9G:
Trade size 78 = 2280 mm² allowable area

Table 6B:
350 kcmil = 373 mm²

2280 ÷ 373 = 6.1

Must round down.

✅ Maximum = 6 conductors

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✅ Question 3

24 × No. 12 T90 solid

Table 6K:
No. 12 T90 = 7.12 mm²

7.12 × 24 = 171 mm²

Table 9G:
Minimum conduit size that fits ≥ 171 mm²:

✅ Trade Size 27

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✅ Question 4

16 trade size rigid RTRC marked IPS
53% fill (single conductor case)

From Table 9D:

Maximum allowable area at 53% fill:

✅ 124 mm²

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✅ Question 5

Conductors inside rigid metal conduit:

1 × No. 1 T90 = 101 mm²
8 × No. 3 T90 = 503 mm²
3 × No. 6 T90 = 98 mm²

Total:

101 + 503 + 98 = 702 mm²

From Table 9G:
Minimum conduit size that accommodates ≥ 702 mm²:

✅ Trade Size 53

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✅ Question 6

ENT installation:

12 × No. 10 T90 = 164 mm²
6 × No. 12 TW75 = 70 mm²

Total = 234 mm²

From Table 9G:
Minimum ENT size:

✅ Trade Size 35

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✅ Question 7

63 trade size EMT

Table 9G:
63 EMT = 1513 mm²

Table 6D:
No. 10 TWU75 = 28 mm²

1513 ÷ 28 = 54.03

Round down.

✅ Maximum = 54 conductors

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✅ Question 8

32 × No. 12 T90 solid

Table 6K:
7.12 mm² × 32 = 228 mm²

From Table 9G:
Minimum conduit size:

✅ Trade Size 35

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🎓 Final Summary (Exam Method)

Table 6 → Find conductor area
Multiply by quantity
Table 8 → Check allowable fill percentage
Table 9 → Select conduit size

This is the correct Red Seal / CEC exam method for conduit sizing.

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