Mississippi Residential Electrician

Key Concepts

GFCI Protection (NEC 210.8)

GFCI protection is required in dwelling units at: bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens (within 6 ft of sink), boathouses, bathtubs/shower stalls, laundry areas, and near swimming pools. For non-dwelling locations, GFCI is required in bathrooms, kitchens, rooftops, outdoors, garages, service bays, and similar areas. A bathroom is defined (Article 100) as a space with a sink plus at least one additional fixture (toilet, tub, shower, etc.).

AFCI Protection (NEC 210.12)

All 120V, single-phase, 15A and 20A branch circuits supplying outlets in dwelling unit sleeping rooms, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas, and similar rooms require combination-type AFCI protection. AFCI is a dwelling-unit requirement — not required for non-dwelling occupancies under this section.

Key Concepts

Service Conductor Clearances (Article 230) - Overhead service conductors must maintain clearances above roofs, driveways, and public spaces per 230.24. - Underground service conductors must meet burial depth requirements per Table 300.5. - Service entrance conductors must be protected from physical damage; conduit or cable armor is required where subject to damage (230.50).

Service Disconnecting Means (Article 230, Part VI) - The service disconnect must be located at the nearest point of entrance to the building or structure (230.70(A)). - Maximum of 6 disconnects per service (230.71(A)). - Each disconnect must be rated for the load it serves and must clearly indicate ON/OFF (230.77). - Minimum rating for a one-family dwelling: 100 amperes, 3-wire (230.79(C)).

Key Concepts

Standard Ampere Ratings (NEC 240.6) Standard ratings for fuses and inverse-time circuit breakers: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600A. When a calculated load doesn't match a standard rating, round up to the next standard size — but only if the conductor ampacity allows it (NEC 240.4(B)).

Conductor Protection Based on Ampacity (NEC 240.4) The overcurrent device must not exceed the conductor's ampacity. Key exceptions: - 14 AWG → protected at 15A max - 12 AWG → protected at 20A max - 10 AWG → protected at 30A max These limits apply regardless of higher-rated equipment in the circuit.

Key Concepts

Grounding Electrode System (NEC Article 250, Part III) All grounding electrodes present at a structure must be bonded together to form a single grounding electrode system. Acceptable electrodes include: - Metal underground water pipe (in contact with earth ≥10 ft) - Metal frame of building/structure (effectively grounded) - Concrete-encased electrode (Ufer ground) — ≥20 ft of #4 AWG or larger bare copper, or ≥20 ft of ½" rebar encased in concrete footer - Ground ring (bare copper, ≥2 AWG, encircling building, ≥20 ft buried) - Rod/pipe electrodes — must be ≥8 ft in length; if a single rod cannot achieve 25 ohms resistance, a second rod must be added (250.56)

Key Concepts

Ampacity Tables (NEC 310.16, 310.17, 310.18, 310.19) - Table 310.16 is the primary reference: conductors in raceways, cables, or earth — based on 60°C, 75°C, and 90°C temperature ratings at 30°C ambient. - Table 310.17 covers conductors in free air. - Use the conductor's terminal temperature rating, not the insulation rating, when selecting ampacity. Most residential devices are rated 60°C or 75°C — you cannot use the 90°C column for final ampacity unless terminations are rated for it.

Temperature Ratings & Insulation Types - THHN/THWN-2: 90°C dry/wet — common in raceways - THWN: 75°C wet; THW: 75°C wet/dry - NM-B: 90°C rated insulation, but limited to 60°C ampacity at terminations per 334.80 - Wet locations require W-rated insulation (e.g., THWN, XHHW) - Direct burial: USE, UF, or listed direct-burial cable required - Sunlight exposure: Must be sunlight-resistant (marked "sunlight resistant" or "SW")

Key Concepts

Conduit Types and Permitted Uses (NEC Article 358, 342, 344, 348, 350, 356, 352, 353, 362)

• EMT (Electrical Metallic Tubing): Thin-wall metal conduit; not threaded; permitted in most locations but NOT in areas subject to severe physical damage
• IMC (Intermediate Metal Conduit): Heavier than EMT, can be threaded; suitable for concrete, direct burial, and wet locations
• RMC (Rigid Metal Conduit): Heaviest metal conduit; threaded; permitted in all environments including direct burial and corrosive areas (with proper protection)
• FMC (Flexible Metal Conduit): No liquid protection; minimum ½ in. trade size required for general use; limited to 6 ft in most applications
• LFMC (Liquidtight Flexible Metal Conduit): FMC with liquidtight plastic jacket; permitted in wet/damp locations
• PVC (Rigid PVC Conduit): Nonmetallic; Schedule 40 and Schedule 80; permitted in concrete, direct burial, and wet locations; requires expansion fittings for long runs
• HDPE: Direct burial and encasement; not…

4 questions | 7% of exam | Reference: NEC 2020

Key Concepts

Luminaire Location Requirements

• Wet locations: Luminaires must be listed and marked for wet locations.
• Damp locations: Must be listed for damp or wet locations.
• Corrosive locations: Must be listed for the environment.
• Bathtub/shower zones (410.10(D)): No luminaires within a zone measured 3 ft horizontally and 8 ft vertically from the top of the bathtub rim or shower threshold, unless listed for wet locations.
• Clothes closets (410.16): Only allowed types are surface-mounted or recessed incandescent/LED with enclosed light source, surface-mounted or recessed fluorescent, and LED luminaires. Prohibited: pendant luminaires and incandescent luminaires with open or partially enclosed lamp. Minimum clearances from storage space apply.

Key Concepts

Pools, Spas, Hot Tubs & Fountains (Article 680)

GFCI Protection Requirements: - All 15A and 20A, 125V receptacles within 20 feet of the inside walls of a pool, spa, hot tub, or fountain require GFCI protection (680.22(A)(1)) - All lighting outlets, luminaires, and switching devices within 5 feet of the water's edge require GFCI protection - Underwater luminaires operating above 15V must have GFCI protection (680.23(A)(3)) - All receptacles within 6 feet of a spa or hot tub must be GFCI protected (680.43(A))

Receptacle, Lighting & Switching Device Clearances: - Receptacles: minimum 6 feet, maximum 20 feet from pool edge; must be GFCI protected (680.22(A)) - Switching devices: minimum 5 feet horizontally from pool water (680.22(C)) - Lighting fixtures and ceiling fans: minimum 12 feet above pool water surface; GFCI protection required if between 12–16 feet (680.22(B))

Key Concepts

GFCI Requirements

• GFCI protection is required in bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens (countertop receptacles), and construction sites (NEC Article 210.8).
• On construction sites, all 120V, 15A and 20A receptacles must have GFCI protection OR the contractor must implement an Assured Equipment Grounding Conductor Program (AEGCP) (NEC 590.6).
• An AEGCP requires visual inspection and testing of all equipment before first use, after any incident that could cause damage, and at regular intervals (not exceeding 3 months).

Lockout/Tagout

• Before working on deenergized equipment, the circuit must be locked out and tagged to prevent accidental re-energization (OSHA 29 CFR 1910.147 / NEC 110.34).
• A tag alone is not a substitute for a lock when a lockout device is feasible.
• Verify the circuit is de-energized with a meter after lockout is applied.