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400 — Flexible Cords and Cables

400.7Flexible cords are not a substitute for permanent wiring—use only where specifically permitted.
400.8Never use flexible cords where concealed, run through holes, attached to building surfaces, or subject to damage.
400.10Flexible cords must be suitable for the environment and properly supported to prevent strain on connections.
400.14Use hard usage cords for portable equipment; extra-hard usage for construction sites and harsh environments.
400.22Flexible cords must be continuous from outlet to equipment—no splices except in listed cord connectors.

EXAM TRAP

Flexible cord violations

The most common flexible cord violation is using it as permanent wiring. Remember: cords are for temporary connections to portable equipment only.

Flexible cords for portable equipment only.

Proper strain relief prevents connection damage.

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404 — Switches: Ratings, Grounding, and Accessibility

404.6Switches must be used within their listing and voltage/ampere ratings—never exceed nameplate values.
404.9(B)Provide an equipment grounding conductor to metal boxes/yokes; bond metal cover plates to prevent shock hazards.
404.8(A)Switches must be readily accessible—no ladders, tools, or moving objects required to operate them.
404.10(B)Face-up switches in countertops are prohibited unless specifically listed for that application.
404.14Switch marking must indicate ON/OFF positions and be visible from the normal operating position.

RULE OF THUMB

Switch accessibility

Readily accessible means you can reach it without tools, ladders, or moving furniture. If you need a step stool, it's not readily accessible.

Switches at accessible height without tools.

Metal switch yokes must be grounded.

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406 — Receptacles: Types, Ratings, and Installation

406.3Receptacles must be listed and identified for the specific use—GFCI, weather-resistant, tamper-resistant, etc.
406.4Provide GFCI protection for all 125V, 15A and 20A receptacles in bathrooms, kitchens, garages, and outdoor locations.
406.5Receptacles must be grounded unless specifically permitted to be ungrounded—never remove the ground pin.
406.9Install receptacles so the grounding slot is up in commercial installations to prevent objects from falling across contacts.
406.12Use tamper-resistant receptacles in dwelling units to prevent children from inserting objects into slots.

NEC REFERENCE

GFCI requirements

210.8 lists all GFCI requirements. In dwelling units: bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens, laundry areas, and within 6 feet of sinks.

GFCI protection required in wet locations.

Tamper-resistant receptacles prevent shock hazards.

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410 — Luminaires: Installation and Clearances

410.16Maintain clearances from combustibles per luminaire listing—typically 6 inches minimum for most fixtures.
410.24Support luminaires by listed means—never rely on raceway, cable, or cord for support unless specifically listed.
410.30Provide grounding for metal luminaires—use equipment grounding conductor or listed grounding methods.
410.36Install damp location luminaires in bathrooms, covered porches, and similar areas; wet location for outdoors.
410.44Use listed lampholders and ensure proper wattage ratings—never exceed fixture or lampholder ratings.

TABLE

Luminaire Clearances

Location	Minimum Clearance	Notes
Combustible material	6 inches	Per fixture listing
Insulation	3 inches	Unless fixture listed for contact
Clothes closets	12 inches	From storage area

Clearances are minimum distances. Always check the fixture listing for specific requirements.

Maintain clearances from combustibles.

Use listed wet location fixtures outdoors.

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422 — Appliances: Disconnects and Nameplates

422.31Provide disconnecting means for appliances—within sight or lockable when not within sight of the appliance.
422.33Use nameplate ratings for conductor and OCPD sizing—never use generic tables when nameplate values are available.
422.16Install appliances per listing and instructions—enclosure ratings, clearances, and mounting requirements matter.
422.62Provide GFCI protection for dishwashers, garbage disposals, and similar appliances in dwelling unit kitchens.
422.11Use listed appliances only—never modify or alter listed equipment in ways not covered by the listing.

CHART

Appliance Disconnect Rules

Appliance Rating	Disconnect Required	Location
≥300 VA	Yes	Within sight or lockable
<300 VA	No	Unless specified in listing
Cord-and-plug	May serve as disconnect	When within sight

Within sight means you can see the disconnect from the appliance without moving more than 50 feet.

Disconnect within sight of appliance.

Always use nameplate ratings for sizing.

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424 — Fixed Electric Space Heating

424.3(B)Size branch circuits at 125% of the continuous heating load—space heaters typically run continuously.
424.19Provide disconnecting means within sight of the heater or make it lockable when not within sight.
424.9Maintain clearances from combustibles per heater listing—typically 12 inches minimum for most units.
424.20Use listed heating equipment only—never modify or alter listed heaters in ways not covered by the listing.
424.22Install thermostats per listing—some require specific wiring methods or clearances from heat sources.

RULE OF THUMB

Continuous load sizing

Space heaters are continuous loads (3+ hours). Always size at 125% of the nameplate rating for branch circuit conductors and OCPD.

Maintain clearances from combustibles.

Disconnect within sight or lockable.

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430 — Motors: OCPD, Conductors, and Disconnects

430.52Motor OCPD sizing per Table 430.52—protects the circuit conductors, not the motor windings.
430.22Size motor conductors at 125% of the motor FLC from Tables 430.248-250—not nameplate values.
430.102(B)Provide disconnect within sight of motor and driven machinery—exceptions for specific applications.
430.32Motor overload protection protects the motor windings—separate from and in addition to OCPD.
430.6Use Table FLC values for conductor and OCPD sizing—nameplate values only for overload protection.

EXAM TRAP

Motor protection confusion

OCPD protects the wiring; overloads protect the motor. Don't confuse these two different protection systems.

Overloads protect motor; OCPD protects circuit.

Disconnect within sight of motor.

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440 — Air-Conditioning and Refrigeration Equipment

440.6Use nameplate values (RLA, FLA, MCA, MOCP) for conductor and OCPD sizing—not generic motor tables.
440.14Provide disconnect within sight of the equipment—some exceptions for rooftop and similar installations.
440.4(B)Install per listing and instructions—enclosure integrity and spacing critical for proper cooling airflow.
440.12Use listed A/C equipment only—never modify or alter listed equipment in ways not covered by the listing.
440.35Provide GFCI protection for 125V, 15A and 20A receptacles within 25 feet of A/C equipment.

NEC REFERENCE

Nameplate values rule

When nameplate shows MCA (Minimum Circuit Ampacity) and MOCP (Maximum Overcurrent Protection), use these values—don't calculate from motor tables.

Use nameplate MCA/MOCP values.

Disconnect within sight of equipment.

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450 — Transformers: Ventilation, OCPD, and Terminations

450.9Provide ventilation and maintain clearances from combustibles per transformer listing—critical for cooling.
450.3Size primary/secondary OCPD per Table 450.3(A)/(B)—depends on transformer type and voltage class.
110.14Follow termination temperature ratings and torque requirements—use lugs listed for conductor material.
450.13Install dry-type transformers per listing—mounting orientation and clearances affect cooling performance.
450.21Provide grounding per Article 250—transformer cases and secondary neutral/grounded conductors must be grounded.

TABLE

Transformer OCPD Sizing

Transformer Type	Primary OCPD	Secondary OCPD
Dry-type <600V	125% of primary FLA	125% of secondary FLA
Dry-type ≥600V	250% of primary FLA	125% of secondary FLA
Liquid-filled	See Table 450.3(B)	See Table 450.3(B)

Table 450.3 has the complete rules—check the notes for exceptions and special applications.

Maintain clearances for proper cooling.

OCPD sizing per Table 450.3.

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408 — Panelboards and Switchgear

408.36(D)Service disconnect rules apply when equipment is service rated—labeling and grouping requirements matter.
408.54Install filler plates in all unused panelboard openings—no tape, cardboard, or makeshift covers allowed.
110.26Maintain working space and dedicated space above panels—no storage or other equipment in front of panels.
408.4Use listed panelboards and switchgear only—never modify or alter listed equipment in ways not covered by the listing.
408.3Provide proper labeling—circuit directories must be accurate and legible for safe operation and maintenance.

JOBSITE HORROR STORY

The missing filler plate

An inspector found electrical tape covering a breaker space where a filler plate should've been. Failed the entire floor and delayed energization by a week. Always keep spare filler plates on hand.

Every opening needs a listed filler plate.

Maintain clear working space in front of panels.

Chapter 4 — Equipment for General Use

400 — Flexible Cords and Cables

404 — Switches: Ratings, Grounding, and Accessibility

406 — Receptacles: Types, Ratings, and Installation

410 — Luminaires: Installation and Clearances

422 — Appliances: Disconnects and Nameplates

424 — Fixed Electric Space Heating

430 — Motors: OCPD, Conductors, and Disconnects

440 — Air-Conditioning and Refrigeration Equipment

450 — Transformers: Ventilation, OCPD, and Terminations

408 — Panelboards and Switchgear

Knowledge Check

Outdoors in a wet location, a 20A, 125V receptacle is installed on a dwelling. Which cover is required?

A countertop requires a face‑up receptacle. Which statement is correct?

Which best describes 'readily accessible' for a wall switch?

A luminaire is supported by EMT. When is this permitted?

An appliance is 240V, 16A, fixed, and within sight. What can serve as its disconnect?

Fixed electric space‑heating load is 32A continuous. Minimum circuit ampacity?

Motor branch‑circuit conductor ampacity is based on:

For A/C equipment, which values control conductor/OCPD sizing?

Transformer primary OCPD sizing is generally taken from:

A panelboard has an unused breaker opening. What’s required?

An ICP (industrial control panel) nameplate shows SCCR = 10 kA, available fault = 22 kA. Result?

Which statement about motor branch OCPD is true?

Closet luminaire rules generally restrict:

A WR receptacle is installed outdoors but under a roof (damp location). Cover?

Fixed space heating at 48A continuous—minimum OCPD (standard ratings)?