Multiple distribution boxes in one level are prohibited

It is prohibited to install multiple distribution boxes on the same level controlling the same electrical equipment to ensure safety, proper isolation, and compliance with electrical standards.

Principle Behind the Prohibition

The rule follows the principle of "one machine, one switch, one leakage, one box, and one lock", which means that a single switchgear or distribution box should not directly control two or more pieces of electrical equipment, including sockets . This ensures that each piece of equipment has dedicated protection, isolation, and control, reducing the risk of electrical faults, overloads, or accidental energization.

Distribution Box Levels

• Primary Distribution Box (Level I): Receives three-phase power, ground, and neutral from the transformer. It provides main circuit isolation, main circuit breakers, and fuses .
• Secondary Distribution Box (Level II): Distributes power from the primary box to temporary or secondary circuits. It includes general isolation, fuses, and circuit breakers .
• Tertiary Distribution Box (Level III): Controls individual electrical equipment and includes isolation and leakage protection .

Each level has specific configuration requirements to maintain safety and operational integrity. Installing multiple boxes on the same level could compromise these protections and violate the intended isolation hierarchy.

Regulatory and Safety Considerations

Standards such as IEC 60364, BS 7671, and the National Electrical Code (NEC) emphasize proper spacing, accessibility, and isolation for distribution boards . Key points include:

• Adequate working space around panels for maintenance and inspection.
• Clear isolation of circuits to prevent accidental contact or overload.
• Compliance with height, clearance, and environmental requirements to ensure safe operation.

By limiting one distribution box per level, these standards help prevent electrical hazards, simplify maintenance, and ensure that each circuit can be safely isolated without affecting other equipment.

Summary

Installing multiple distribution boxes on the same level is prohibited because it:

• Violates the one box per equipment principle.
• Reduces the effectiveness of isolation and protection devices.
• Increases the risk of electrical faults and hazards.
• Conflicts with IEC, BS 7671, and NEC standards for safe electrical installations .

Following this rule ensures a safer, more reliable electrical system and compliance with international and national electrical codes.