Which of the following is NOT a factor to consider when determining wire size?

• A. System voltage
• B. Ambient temperature
• C. Wire color
• D. Maximum altitude

Answer: (C)

Wire size is determined by how much current the circuit must safely carry and how heat will be dissipated under the expected conditions. The conductor must handle the ampacity without overheating, so you start with the load current and whether the load is continuous, then apply temperature and installation deratings (ambient temperature, whether conductors are bundled, and the installation method) and choose a gauge with adequate ampacity from the applicable tables, using the insulation’s temperature rating. You also consider the system voltage to ensure the insulation is rated for that voltage and to assess voltage drop over the run, and altitude because thinner air at higher elevations reduces cooling. Wire color, however, does not affect any of these factors; it’s just a coding/identification feature and has no impact on current-carrying capacity or voltage rating.