Electrical distribution box assembly drawing with dimensions

Electrical distribution box dimensions are typically specified in the construction drawings, with illustrative examples showing tolerances of ±10% depending on KVA rating and manufacturer design.

General Construction and Material

Distribution boxes are generally fabricated from 2 mm GI sheet steel or CRCA MS, reinforced with suitable channels for structural stability. The roof is slightly slanted with a 50 mm overhang at the front and back, 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, conforming to IP-55 protection standards for outdoor use .

Typical Dimensions and Tolerances

• The dimensions of LT distribution boxes are often illustrative in specifications, allowing manufacturers to propose their own sizes within a ±10% tolerance over the specified dimensions .
• For 63/100/160/315 KVA boxes, the internal layout accommodates busbars, isolators, and outgoing feeders, with busbar sizes ranging from 72×50×8 mm for 63/100 KVA to 120×50×15 mm for 160/315 KVA boxes .
• Terminal connector strips on isolators project 80 mm minimum on the cable connection side and 60 mm minimum on the HRC fuse base side, ensuring proper clearance and connectivity .

Layout Considerations in Drawings

• Construction drawings typically show front, side, and top views of the distribution box, including internal busbar arrangements, isolator positions, and fuse placements.
• Symbols on the drawings indicate equipment type and connection points, but dimensions must be read directly from the drawing for precise installation .
• Detailed drawings may also include punching marks, nameplates, and lighting provisions inside the cabinet for maintenance and identification .

Key Takeaways

• Always refer to the specific project drawings for exact dimensions, as specifications provide illustrative sizes and tolerances.
• Ensure that the internal layout meets the required KVA rating and complies with IS standards for isolators, fuse bases, and busbars.
• Verify that the IP rating, earthing, and locking mechanisms are consistent with the construction drawings and project requirements. By following these guidelines, the electrical distribution box can be accurately fabricated and installed according to the construction drawings while maintaining compliance with safety and operational standards .