07 - Modern Wiring Methods: NM, AC, MC Cable, Conduit Types

Send us Fan MailModern wiring methods include various cable types and conduit systems, each with specific uses, limitations, and installation requirements. This episode covers the most common wiring methods home inspectors encounter and how to identify improper installations.What You'll LearnNonmetallic Sheathed Cable (NM) and Underground Feeder (UF):NM (Romex): Predominant wiring since 1940sEarly versions (late 1920s-1960s): Cloth sheathingModern NM: PVC sheathingColor coding: White=#14, Yellow=#12, Orange=#10, Black=#8 and #6Notation: 14/2 or 14-2 (gauge/quantity of insulated conductors, plus EGC)UF: Similar to NM, designed for wet locations and burialUF may NOT be embedded in concrete (but may be in conduit embedded in concrete)UF jacket usually grayUF may NOT be used for pool/hot tub/spa wiring (uninsulated EGC)Armored Cable (AC):Found from early 1900s to new constructionSometimes called BX (brand name—General Electric)Factory assembly with flexible interlocking metal coveringConductors wrapped in paperShould have anti-short bushing at terminationsAC jacket can serve as EGC (if manufactured after 1959)Pre-1959 AC: Watch for rust/damage increasing resistanceMetal-Clad Cable (MC):Found from early 1900s to new constructionSometimes called Greenfield (early MC form)Factory assembly with flexible metal covering (aluminum or steel)NOT paper-wrapped (unlike AC)Difficult to distinguish from AC and FMC visuallyMC jacket can serve as EGC with appropriate fittingsElectrical Metallic Tubing (EMT):Sometimes called "thin wall"Round pipe for routing/protecting conductorsSteel or aluminumCommon sizes: ½" to 4" diameter, 10-foot sectionsMay serve as EGC with appropriate fittingsIntermediate Metal Conduit (IMC) and Rigid Metal Conduit (RMC):Round pipes for routing/physical protectionIMC: Thinner wall, lighter weight alternative to RMCSteel (including galvanized) or aluminumCommon sizes: ½" to 4" diameterMay serve as EGC with appropriate fittingsIMC/RMC Installation Requirements:Support every 10 feetSupport within 3 feet from boxes/terminationsFlexible Metal Conduit (FMC):Flexible tube of helically wound interlocking metalSteel or aluminum (including galvanized/stainless)Common sizes: ½" to 4" diameterLiquidtight Flexible Metal Conduit (LFMC) and Liquidtight Flexible Conduit (LFC):Flexible tubes for water-resistant applicationsLFMC: Galvanized steel with water-resistant PVC jacketLFC: PVC materialCommon sizes: 3/8" to 4" diameterLFMC may serve as EGC with appropriate fittingsCommon locations: Exterior HVAC equipment, pools, hot tubsKey TakeawaysNM is most common wiring method (color-coded jackets)AC, MC, and NM have different allowed locations and limitationsSupport spacing varies by wiring method (remember key intervals)Flexible cords may NOT be used as permanent wiring"Subject to physical damage" requires judgment and interpretationBurial depths vary by wiring methodMetal conduit/tubing can serve as EGC with proper fittingsIntro This episode is brought to you by GetSync.pro This episode is hosted by Charlie Bellefontaine of Chicagoland Home InspectorsFor complete training with visual materials, practice exams, and certification support, visit nhiexamprep.com© 2025 National Home Inspector Exam Prep Podcast. All rights reserved.