90 Modern Commercial Wiring Copyright Goodheart-Willcox Co., Inc. load requirements. Conductors run in parallel must meet the following criteria: • Conductors must be 1/0 AWG and larger • Conductors must be the same size • Conductors must have the same insulation type • Conductors must be the same material • Conductors must be the same length • Conductors must be terminated in the same manner. Paralleled conductors can be installed in separate conduits or in a single conduit. If the conductors are installed in the same conduit, the electrician should observe Section 310.15(B) (3)(a) of the Code regarding allowable ampacities of conductors. 6.2.4 Conductor Size Limits With some exceptions, Section 310.106(A) of the Code lists the smallest conductor permitted for general wiring as 14 AWG copper or 12 AWG aluminum or copper-clad aluminum. The exceptions allow smaller sizes for flexible cords, fl fixture wire, fractional horsepower motors, fi cranes and hoists, elevator control and signal circuits, remote control circuits, protective sig- naling, and motor control circuits. The table in Figure 6-7 contains minimum conductor sizes. 6.2.5 Shielding The Code states that conductors operated above 2000 volts in permanent installations must have ozone-resistant insulation and be shielded. Fur- ther, those with metal shields must be grounded. 6.2.6 Direct Burial Section 310.10(F) of the Code states that conduc- tors used in direct burial applications must be specifically approved for the purpose. In addi- fi tion, these conductors, if rated above 2000 volts, must be shielded and the shield properly grounded. However, direct burial conductors rated between 2000 volts and 5000 volts do not require shielding if the cable has an overall metallic shield or armor. 6.2.7 Wet Locations Conductors used in wet conditions must be either lead-covered or marked with a “W” (RW, TW, and THW for example), indicating they are suitable for wet locations. 6.2.8 Corrosive Conditions Conductors that will be used in severe envi- ronments, in the presence of corrosive agents, and in situations where insulation deterioration is likely must be covered with insulation spe- cifi listed and suitable for such conditions. fically These conductors are marked with a “C.” CODE ALERT Wet Location According to Article 100, wet locations include installations underground or in concrete slabs or masonry in direct contact with the earth and locations subject to saturation with water or other liquids, such as vehicle washing areas and unprotected locations exposed to weather. Goodheart-Willcox Publisher Figure 6-7. Minimum conductor sizes for various applications. Minimum Conductor Size Minim ni mu m Con Co nd uctor Size Conductors for general wiring r in g 14 AWG (copper) 12 AWG (aluminum or copper-clad) Crane an e and hoist control circuits 16 AWG Flexible cords Fixture wires 18 AWG Elevator control and signaling circuits 20 AWG Fire protection signaling circuits Remote control and signal circuits 14 14 AWG A