Standard requirements for the size of electrical distribution boxes in building corridors

Electrical distribution boxes in corridors are typically fabricated from 2 mm GI sheet steel, with IP-55 protection, and sized according to KVA rating and busbar requirements.

Physical Construction

Distribution boxes for corridor installations are generally fabricated from 2 mm galvanized iron (GI) sheet steel with reinforced channels for structural stability and provisions for secure mounting and handling . The roof is often slightly slanting with a 50 mm overhang to prevent water ingress, and doors are equipped with Godrej-type 3-position locking systems for security . Hinges are concealed, and boxes include solid earthing points on either side. The boxes are designed to meet IP-55 protection, ensuring dust and water resistance .

Electrical Specifications

• Busbars: Made of EC grade aluminum, with sizes depending on KVA rating:
  • 63/100 KVA: 72 x 50 x 8 mm
  • 160/315 KVA: 120 x 50 x 15 mm
• Feeders and droppers:
  • Feeder droppers: 50 x 8 mm for 63/100 KVA, 50 x 15 mm for 160/315 KVA
  • Incomer droppers: 50 x 8 mm for 63/100 KVA, 50 x 15 mm for 160/315 KVA
• Isolators: Switch disconnectors conforming to IS:13411, with arc-chutes for safe operation and a minimum handle length of 300 mm on the cable connection side .
• Protection devices: Porcelain cutouts for outgoing circuits in higher KVA boxes, and provision for MCCBs (4-pole for incoming, 3-pole for outgoing) as per LT supply rules .

Dimensions and Layout

While exact corridor box dimensions vary by manufacturer and KVA rating, typical LT distribution boxes are designed to accommodate busbars, droppers, and MCCBs with adequate clearance from the enclosure walls to comply with electrical safety standards . The internal layout ensures phase sequence RYB and proper insulation using PVC sleeves. Boxes are generally wall-mounted in corridors, with sufficient space for wiring, heat dissipation, and maintenance access .

Key Considerations for Corridor Installations

• Ensure IP-55 or higher for dust and water protection.
• Maintain adequate clearance around busbars and feeders for safety and maintenance.
• Use robust locking and earthing to prevent unauthorized access and ensure grounding.
• Select box size based on KVA rating, number of outgoing circuits, and busbar dimensions.
• Verify compliance with local electrical codes and standards for corridor installations. These specifications ensure that distribution boxes in corridors are safe, durable, and compliant with electrical standards, while providing sufficient space for wiring and circuit protection.