Final answer:
Receptacle boxes and junction boxes must be installed according to the NEC in locations specified by local codes, using a three-wire system for safety, and may require GFCI protection in certain areas.
Step-by-step explanation:
In residential electrical systems, receptacle boxes and junction boxes must be installed in accordance with the National Electrical Code (NEC) to ensure electrical safety. These boxes provide a safe enclosure for electrical connections and must be easily accessible, not hidden behind walls or ceilings. Receptacles, typically known as outlets, are installed within receptacle boxes spaced apart as specified by local code, usually every 12 to 16 feet along walls in living areas, and within a certain distance from sinks in kitchens and bathrooms, to minimize the use of extension cords and reduce the risk of shock. In addition to receptacle placements, junction boxes are used to connect and protect wire splices and are required to be covered with an accessible plate for maintenance and inspection purposes.
The three-wire system is crucial in this setup, as it includes a live/hot, neutral, and earth/ground wire. This system enhances safety by grounding the appliance case and the neutral wire, preventing potential shocks, especially if the insulation on the live wire wears out and comes into contact with an appliance case. Large appliances and circuits supporting water-exposed areas often require a ground fault circuit interrupter (GFCI), which quickly interrupts power to prevent shock. It is important to adhere to code requirements and proper color coding of wires for safe identification and connection of the appropriate circuits.