Final answer:
In buildings with systems of above one nominal voltage, each ungrounded conductor in a multi-wire branch circuit should be identified by appropriate color codes that vary by region, with typically white or gray for neutral, green or green-yellow for ground, and other colors for live/hot wires.
Step-by-step explanation:
In buildings that contain systems of more than one nominal voltage, a multi-wire branch circuit should have each ungrounded (hot) conductor identified. Identification helps to safely manage the multiple voltage systems involved and reduces the risk of electrical hazards. Typically, wire color codes are used for this purpose. However, wire insulation colors can vary by region, and it is essential to check local regulations to determine which color codes are in use. According to electrical safety standards, such as the National Electrical Code (NEC), grounded conductors (neutral) are usually white or gray, and equipment ground conductors are typically green or green with a yellow stripe. The live/hot wires are often black, red, or another color, but not green, white, or gray.
Multi-wire branch circuits are part of a three-wire system that includes a neutral wire grounded at the voltage source and user location, forcing it to be at zero volts and furnishing an alternate return path for current through the earth. The case of the appliance is also grounded to zero volts for safety, preventing electrical shock. The system is protected by circuit breakers or fuses against thermal overloads, and these protective devices are placed in series with the live/hot wires. Ground fault circuit interrupters (GFCIs) may be used to detect and prevent shock by quickly interrupting power in the presence of a ground fault.