← Wiring Methods – Electrician Journeyman Exam Flashcards

Electrician Journeyman Exam Study Guide

Key concepts, definitions, and exam tips organized by topic.

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Wiring Methods – Electrician Journeyman Exam Study Guide


Overview

This study guide covers the essential wiring methods tested on the Journeyman Electrician Exam, including conduit types, cable assemblies, installation requirements, and NEC code compliance. Mastery of these topics requires understanding not only what each wiring method is, but where it can and cannot be used, and the specific numerical values (spacing, fill percentages, bend limits) that frequently appear on exams.


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1. Conduit Types & Properties


Metal Conduit Comparison


| Conduit Type | Wall Thickness | EGC Listed? | Key Feature |

|---|---|---|---|

| RMC | Thickest | ✅ Yes | Lowest burial depth; most protection |

| IMC | ~25% thinner than RMC | ✅ Yes | Lighter than RMC; same applications |

| EMT | Thinnest | ❌ No (fitting required) | Most common; not for severe damage |

| FMC ("Greenfield") | N/A (flexible) | Conditional | Spiral metal, no jacket |

| LFMC | N/A (flexible) | Conditional | Spiral metal + liquid-tight jacket |


Nonmetallic Conduit


  • • PVC (Schedule 40/80): Rated to 50°C (122°F) ambient for direct burial; above this, a higher-rated type is required
  • • LFNC: Smooth or corrugated inner surface with a liquid-tight jacket; no metal armor layer (distinguishes it from LFMC)

    • Key Terms

  • • RMC – Rigid Metal Conduit; thickest wall; listed as Equipment Grounding Conductor (EGC)
  • • IMC – Intermediate Metal Conduit; ~25% thinner than RMC; also listed as EGC
  • • EMT – Electrical Metallic Tubing; lightest metal raceway; requires fittings for grounding
  • • FMC – Flexible Metal Conduit; helically wound interlocked metal strip; trade name "Greenfield"
  • • LFMC – Liquidtight Flexible Metal Conduit; FMC + outer liquid-tight jacket
  • • LFNC – Liquidtight Flexible Nonmetallic Conduit; no metal armor

    • > Watch Out For: Students often confuse LFMC and LFNC. Remember: LFNC has NO metal — the key difference is the absence of a spiral metal core. Also, IMC being ~25% thinner than RMC does not disqualify it as an EGC — it still qualifies.


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    2. Support & Securing Requirements


    Support Spacing Quick Reference


    | Wiring Method | Max Support Spacing | Must Be Secured Within... |

    |---|---|---|

    | RMC (½" – ¾") | 10 feet (3 m) | 3 feet of boxes/cabinets |

    | EMT (½" – ¾") | 10 feet (3 m) | 3 feet (900 mm) of each box |

    | FMC | 4.5 feet (1.4 m) general | 6 feet allowed at luminaires |

    | Type NM (Romex) | 4.5 feet (1.4 m) | 12 inches (300 mm) of each box |

    | Type AC (BX) | 4.5 feet (1.4 m) | 12 inches (300 mm) of each box |


    Critical Numbers to Memorize

  • • EMT secured within: 3 feet of boxes
  • • NM and AC cables secured within: 12 inches of boxes
  • • FMC at luminaires: 6 feet maximum unsupported length
  • • RMC and EMT spacing: 10 feet for ½" – ¾" trade sizes

    • > Watch Out For: EMT (3 feet) and NM/AC cable (12 inches) have different "must be secured within" distances. This is a very common exam trap — don't mix them up!


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    3. Bending & Fill Rules


    Conduit Fill Percentages (NEC Chapter 9, Table 1)


    | Number of Conductors | Maximum Fill % |

    |---|---|

    | 1 conductor | 53% |

    | 2 conductors | 31% |

    | 3 or more conductors | 40% |


    Bend Limitations

  • • Maximum total bends: 360° (equivalent to four 90° bends) between pull points
  • • Pull points include: boxes, conduit bodies, junction boxes
  • • 1-inch EMT minimum inside bend radius (one-shot/hand bender): 4 inches

    • Compact vs. Standard Conductors

  • • Compact conductors have a smaller cross-sectional area than standard (concentric) conductors of the same AWG
  • • Always use NEC Chapter 9 listed values for compact conductors in fill calculations — do not substitute standard conductor dimensions

    • Key Terms

  • • Pull point – A box, conduit body, or fitting where conductors can be pulled through during installation
  • • Compact conductor – A conductor manufactured to a smaller diameter than standard stranded conductors of the same AWG
  • • Inside bend radius – The minimum radius measured to the inside of the conduit bend

    • > Watch Out For: Many students memorize only the 40% fill rule. Remember that one conductor = 53% and two conductors = 31% — these numbers are counterintuitive! Also note: 360° total does NOT mean four bends maximum between any two points; it means the equivalent of four 90° bends.


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    4. Cable Assemblies


    Type Comparisons


    | Cable Type | Direct Burial? | Wet Locations? | Special Feature |

    |---|---|---|---|

    | NM (Romex) | ❌ No | ❌ No | Dry interior use only |

    | NMC | ❌ No | Limited | Fungus/corrosion resistant |

    | UF | ✅ Yes | ✅ Yes | Underground feeder |

    | AC (BX) | ❌ No | ❌ No | Requires anti-short bushing |

    | SE | Limited | Limited | Service entrance; interior use follows 60°C/75°C rules |


    Type AC Cable (BX) — Important Details

  • • Aluminum bonding strip: Maintains electrical continuity and supplements grounding through the armor
  • • Anti-short (red) bushing: Protects conductor insulation from sharp edges of cut armor at terminations
  • • Both components are required at every termination

    • Type SE Cable — Interior Use

  • • When used as interior branch-circuit wiring (not at service entrance), conductors must comply with:

    • - 60°C or 75°C column of NEC Table 310.12 (based on cable's temperature rating)


    The 'G' Suffix

  • • A 'G' at the end of a cable designation (e.g., 12/2G, UF-G) indicates the cable includes an equipment grounding conductor
  • • Example: "12/2 with ground" = two current-carrying conductors + bare/green ground

    • > Watch Out For: Type UF and Type NM look similar but have entirely different permitted uses. UF = Underground Feeder (can be buried); NM cannot be buried or used in wet locations. Also, the anti-short bushing in AC cable is a code requirement, not optional.


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    5. Permitted & Prohibited Uses


    Type NM Cable Prohibited Locations

  • • Buildings over three floors above grade
  • • Type I or II construction (noncombustible) regardless of height
  • • Commercial or industrial occupancies subject to physical damage
  • • Wet or damp locations; direct burial

    • FMC Prohibited Locations

  • • Wet locations
  • • Hoistways (except as permitted by NEC Article 620)
  • • Where exposed to deteriorating materials
  • • Where subject to physical damage

    • LFMC Length Limitation

  • • Maximum 6 feet (1.8 m) in any single run
  • • Exception: Greater lengths permitted where used for equipment flexibility connections (AHJ approval may be required)

    • PVC Conduit Prohibited Uses

  • • Direct support of luminaires or equipment unless specifically listed for PVC support
  • • Hazardous classified locations (Class I, Division 1) unless specifically listed

    • Plenum Wiring

  • • Most power wiring in plenums must be installed in metal raceway
  • • Cables permitted in plenums without conduit:

    • - Type MI cable (Mineral Insulated)

    - Plenum-listed cables (e.g., CMP, FPLP for communications/fire alarm)

    - Type CI (Circuit Integrity) cable


    Minimum Burial Depths (NEC Table 300.5)


    | Wiring Method | Under Residential Driveway |

    |---|---|

    | RMC | 6 inches (150 mm) — lowest requirement |

    | IMC | 6 inches |

    | PVC Schedule 80 | 18 inches (standard) |

    | Direct burial cable | 24 inches (standard) |


    > Watch Out For: RMC has the shallowest burial depth requirement of all wiring methods — just 6 inches under a residential driveway. Students often assume more protection means deeper burial, but the NEC recognizes RMC's physical strength. Also, LFMC's 6-foot maximum applies to the overall run length, not just at connections.


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    6. Equipment Grounding Conductor (EGC) Summary


    | Conduit/Cable | Listed as EGC? |

    |---|---|

    | RMC | ✅ Yes — when properly bonded |

    | IMC | ✅ Yes — when properly bonded |

    | EMT | ❌ No (fittings required; must be listed) |

    | FMC | Conditional (≤6 ft, specific sizes) |

    | LFMC | Conditional (≤6 ft, specific sizes) |

    | Type AC cable armor | ✅ Yes — supplemented by bonding strip |


    > Watch Out For: EMT is not listed as an EGC on its own — it must use listed fittings and proper bonding. RMC and IMC are listed as EGCs when properly installed and bonded.


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    Quick Review Checklist


    Use this checklist to confirm you know the most critical exam points:


  • • [ ] PVC conduit max ambient temperature: 50°C (122°F) for direct burial
  • • [ ] FMC trade name: "Greenfield" — spiral metal, no jacket
  • • [ ] RMC has thickest wall; listed as EGC; lowest burial depth (6 inches under driveway)
  • • [ ] IMC is ~25% thinner than RMC but still listed as EGC
  • • [ ] LFNC has no metal armor; LFMC has spiral metal core under jacket
  • • [ ] EMT secured within 3 feet of boxes; supported every 10 feet (½"–¾")
  • • [ ] NM and AC cables secured within 12 inches of boxes; every 4.5 feet
  • • [ ] FMC at luminaires: max 6 feet unsupported
  • • [ ] Maximum bends between pull points: 360° total (4 × 90°)
  • • [ ] Conduit fill: 1 conductor = 53%, 2 conductors = 31%, 3+ conductors = 40%
  • • [ ] Compact conductors: use NEC Chapter 9 table values — smaller area than standard
  • • [ ] 'G' suffix = equipment grounding conductor included
  • • [ ] Type UF = direct burial ✅ | Type NM = NO direct burial ❌
  • • [ ] AC cable requires anti-short (red) bushing AND aluminum bonding strip at terminations
  • • [ ] SE cable used as interior branch circuit → follow 60°C or 75°C ampacity rules
  • • [ ] NM prohibited in Type I/II construction and buildings over 3 floors above grade
  • • [ ] FMC prohibited in wet locations and where subject to physical damage
  • • [ ] LFMC maximum run: 6 feet (except at equipment flexibility connections)
  • • [ ] Plenum power wiring requires metal raceway; Type MI cable permitted in plenums
  • • [ ] PVC not permitted in Class I, Division 1 hazardous locations (unless specifically listed)

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    Study Tip: Focus on the specific numbers — distances, percentages, and temperature ratings are the most frequently tested details on the Journeyman exam. Make flashcards for any value you cannot instantly recall from this checklist.

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