Final answer:
The number and size of conductors in a raceway as per the NFPA 70 are determined by the American Wire Gauge (AWG) system, which specifies the wire's diameter and current-carrying capacity.
Step-by-step explanation:
According to the National Fire Protection Association (NFPA) 70, also known as the National Electrical Code (NEC), the number and size of conductors used in a raceway are determined by the American Wire Gauge (AWG). The AWG is a standardized wire gauge system used in the United States to denote the diameter and cross-sectional area of round wire conductors.
The AWG size is a crucial factor because it influences the current-carrying capacity of the wire. You must select the appropriate wire gauge to match the electrical demand of the appliances and equipment it will serve, taking into account the amps they require for proper operation, and aligning with the current-carrying capacity of the wire. It also ensures compatibility with fuses and circuit breakers that protect the circuit.
The selection process is guided by tables in the NEC that indicate the maximum current each gauge of wire can safely conduct and the number of conductors allowed in a given size raceway. When choosing the size of wire, you should take into consideration factors such as the length of the circuit, the type of load, and possible voltage drop over distance.