Quick Hits

EPISODE 3 — 53%, 31%, 40% EXPLAINED

SLIDE 1 — THE WEIRD ONE

Why does the NEC say:

1 = 53%

2 = 31%

3+ = 40%

🤔

Why does two conductors get LESS room than three?

SLIDE 2 — IT'S NOT A TYPO

These percentages aren't arbitrary wire-count trivia.

The geometry and pulling conditions of conductors inside a raceway matter.

With multiple conductors, the conductors interact with one another and the raceway during installation.

⚡ CONDUIT FILL IS ABOUT PHYSICAL SPACE + INSTALLATION CONDITIONS

SLIDE 3 — MEMORIZE THIS

🧠 53 / 31 / 40

Think:

ONE → 53

TWO → 31

THREE OR MORE → 40

Say it out loud.

Then calculate it.

Then verify it in the NEC.

SLIDE 4 — QUICK QUIZ

You have 2 conductors in a raceway.

Maximum fill?

A️⃣ 20%

B️⃣ 31%

C️⃣ 40%

D️⃣ 53%

👇

31%

📚 Chapter 9, Table 1

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