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What’s in Chapter 9 (and Why it Matters)

Table MapExam workhorses: Table 1 (percent fill), Table 4 (raceway dimensions/areas), Table 5/5A (conductor dimensions), Tables 8 & 9 (resistance/impedance).
WorkflowMost sizing questions = Table 5/5A to get areas → Table 1 percent → Table 4 to pick trade size.
NotesChapter 9 Notes change the math (e.g., 24-in nipples at 60% fill). Read them or miss points.
ScopeThese tables support Chapters 1-4 wiring rules. You apply both: Code rule + the right table.

RULE OF THUMB

Use the Right Trio

For insulated conductors in raceway: Table 5/5A → Table 1 → Table 4. That trio answers 80% of exam sizing prompts.

Know which table does what—then chain them.

Mark Table 1, 4, 5/5A, 8, and 9.

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Table 1 — Percent Fill (The Gatekeeper)

Table 11 conductor: 53%; 2 conductors: 31%; >2 conductors: 40% of the raceway cross-sectional area.
EGC CountsEquipment grounding conductors count as conductors for fill.
Cables in RacewayIf installing a cable in a raceway (not individual conductors), use the cable's overall diameter/area against the same percent limits.
Exam AnglePrompts often hide an extra EGC or mislabel a cable as individual conductors. Count correctly.

CHART

Percent Fill Quick Chart

1 Conductor53%

2 Conductors31%

>2 Conductors40%

Start with the correct percent, or every downstream step is wrong.

53% applies to a single conductor.

More than two conductors → 40% fill.

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Using Tables 4 and 5/5A Together

Step 1Use Table 5 for insulated conductor dimensions/areas (THHN, XHHW, etc.). Use Table 5A for compact conductors.
Step 2Sum the areas (or use largest as required for given conductor count/type).
Step 3Apply Table 1 percent to find the minimum raceway area you need.
Step 4Go to Table 4 and choose a trade size where the allowable area ≥ your requirement (for the correct raceway type: EMT, PVC, etc.).

NEC REFERENCE

Match the Raceway Type

Table 4 has separate columns by raceway type and size. Use the correct material (EMT vs PVC) and the right allowable area column.

Grab area per conductor from Table 5/5A.

Pick the first trade size that meets/exceeds your needed area.

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Critical Notes — Nipples & Rounding

Nipple ≤24 inRaceway 24 in or less (a 'nipple') may be filled to 60% of its area—connectors/couplings don't count toward that 24 in length.
Rounding ConductorsWhen converting decimals to a conductor count, ≥ 0.8 rounds up. Exams bait with 0.79 vs 0.8.
Mixed SizesWhen mixed sizes are present, use each conductor's actual area from Table 5/5A—don't average diameters.
Cable in RacewayFor a cable (not singles), compute using the overall cable area against Table 1 percents.

EXAM TRAP

Nipple 60% & 0.8 Rounding

If it’s truly a ≤24 in nipple, 60% is allowed. If your decimal is ≥0.8, round up the conductor count. Two classic exam traps.

Verify length end-to-end, not including fittings.

0.80 goes up; 0.79 stays down.

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Compact Conductors — Table 5A

Compact ≠ THHNCompact strands have smaller diameter for same AWG. Use Table 5A dimensions/areas, not the standard Table 5 values.
ListingsYour conductor type (e.g., XHHW-2 compact) defines which row applies. Manufacturer/catalog + Table 5A must align.
Fill ImpactSmaller area can reduce raceway size if the exam problem explicitly says 'compact'.
Exam CueIf 'compact' isn't stated, assume standard Table 5.

RULE OF THUMB

Only Compact When Stated

Don’t ‘upgrade’ to compact values unless the question, drawings, or label clearly say compact.

Compact = smaller OD at same AWG.

Confirm type and construction before using 5A.

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Cables in Raceway — Use Overall Diameter

Overall ODFor MC/TC/communications cables in raceway, compute area from the overall cable diameter, then apply Table 1 percent.
One vs Multiple1 cable → 53%, 2 cables → 31%, >2 cables → 40% (same percent rules by count).
Exam GotchaDon't treat a cable as individual THHN conductors unless the problem explicitly says singles.

TABLE

Cable in Raceway — Percent Map

# of Cables in Raceway	Percent Fill
1	53%
2	31%
>2	40%

Work from overall cable area, not sum of internal conductors.

Use cable OD for the area calculation.

Percent rules follow count of **cables**.

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Worked Example — Mixed THHN in EMT

GivenThree 3/0 Cu THHN + one #6 Cu THHN + one #8 Cu THHN in EMT.
Step ATable 5: pull areas for 3/0, #6, #8 THHN; sum the areas.
Step BTable 1: >2 conductors → 40%. Compute min raceway area needed.
Step CTable 4 (EMT): choose first trade size with allowable area ≥ requirement.

NEC REFERENCE

Answer Structure Matters

Show table source, show math, show chosen trade size. That structure earns points even if you fat-finger a decimal.

Call out the table numbers in your work.

Pick the first EMT size where allowable area ≥ required.

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Tables 8 & 9 — Resistance and Impedance

Table 8DC resistance (and some 1-phase AC at unity PF). Used for VD calcs where DC or simple cases apply.
Table 9AC impedance data for 60 Hz 3-phase conductors (R and X). Use for AC VD calcs with power factor considerations.
Exam CueIf the problem mentions 3-phase and PF, that's a Table 9 job.

TABLE

Which Table for Voltage Drop?

Scenario	Use
DC / simple case	Table 8 (resistance)
3-phase AC with PF	Table 9 (impedance R & X)

Pick the proper electrical model or you’ll miss by several percent.

Impedance vs resistance changes the math.

3-phase + PF → Table 9.

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Five Common Exam Traps

Wrong PercentUsing 40% for two conductors (should be 31%).
Ignoring NotesMissing the ≤24 in nipple at 60%.
Wrong Table 4 ColumnMixing up EMT vs PVC or using internal diameter instead of allowable area.
Compact ConfusionUsing Table 5A values when the problem never says 'compact' (or vice-versa).
Cable vs SinglesTreating a cable as individual conductors for area math.

EXAM TRAP

Fast Trap Check

Percent? Notes? Raceway type? Compact? Cable vs singles? — Clear these five and most Chapter 9 problems fall in line.

A quick pre-flight catches most misses.

Run the trap checklist before answering.

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Jobsite Horror — The Unpullable Conduit

OverfillOver 40% fill with >2 conductors leads to jammed pulls, damaged insulation, and failed inspections.
Wrong MaterialSizing from EMT column but installing PVC = you picked the wrong allowable area.
Fix CostRe-pull with larger raceway or break the run—both burn schedule and budget.

JOBSITE HORROR STORY

Pull Planning Beats Re-Pulls

Do the Chapter 9 math before bending pipe. It’s faster to size right than to explain why the wire won’t pull.

Overfill kills insulation and schedule.

Right math once > wrong pull twice.

Chapter 9 — Tables & Raceway Sizing

What’s in Chapter 9 (and Why it Matters)

Table 1 — Percent Fill (The Gatekeeper)

Using Tables 4 and 5/5A Together

Critical Notes — Nipples & Rounding

Compact Conductors — Table 5A

Cables in Raceway — Use Overall Diameter

Worked Example — Mixed THHN in EMT

Tables 8 & 9 — Resistance and Impedance

Five Common Exam Traps

Jobsite Horror — The Unpullable Conduit

Chapter 9 — Exam Quick Hits

Percent Fill

Sizing Flow

Notes Matter

Compact Only If Stated

VD Tables

Trap Check

Knowledge Check

With more than two conductors in a raceway, the maximum fill per Table 1 is:

Two conductors in a raceway are limited to what percent fill?

A raceway 24 inches or less in length may be filled to:

When converting a decimal conductor count to a whole number, a decimal of 0.80 should be:

For insulated conductor dimensions/areas you should use:

The table used to pick a raceway trade size from allowable area is:

You are given XHHW-2 compact conductors. Which table supplies the correct areas?

For a cable (e.g., MC) inside a raceway, the fill calculation should use:

Which trio reflects the standard sizing workflow for singles in raceway?

DC resistance values for voltage-drop math are taken from:

AC 3-phase voltage-drop with power factor typically requires data from:

If a problem doesn’t specify ‘compact’ conductors, you should default to:

Which is a common Chapter 9 exam trap?

When mixed conductor sizes are present, you should:

Picking an EMT trade size after calculating required area is done from: