Concealed wiring in household distribution boxes involves careful conduit placement, proper box sizing, and secure mounting to ensure safety, durability, and aesthetic appeal.
Planning and Wall Preparation
Before installation, mark the wall accurately for conduit runs and distribution box placement. Wall chasing should be done carefully to avoid structural damage, especially near lintels, columns, or roof beams. The depth of the chase should not exceed 1.25 inches for a 4.5-inch wall when using 1-inch conduits, ensuring structural integrity and avoiding cracks .
Conduit and Wiring Installation
- Conduits: Use PVC or GI conduits with adequate thickness (e.g., 2 mm for PVC) and size (typically 25 mm for house wiring). Conduits protect wires from mechanical damage and allow future replacement .
- Slab and Wall Runs: Lay conduits in slabs between top and bottom reinforcement, and in walls following straight horizontal and vertical paths. Avoid elbows or unnecessary bends to facilitate smooth wire pulling .
- Color Coding: Use grey PVC for data cables (LAN, telephone) and black PVC for electrical wires to maintain organization .
Distribution Box Specifications
- Sizing: For boxes handling lighting or small power loads with fewer than 20 switches, width = sum of switch widths + 20 mm on each side, height = switch height + 40 mm, depth = max switch depth + 10 mm. For more than 20 switches, two rows are recommended with similar calculations .
- Power Boxes: Consider bending radius for wires larger than 10 mm² and reserve space for terminal connections .
Mounting the Distribution Box
- Wall Fixing: Use expansion bolts (length accounting for wall depth, box base, nut, washer, plus 5 mm clearance). For smaller boxes, wooden blocks can be pre-installed for screw mounting .
- Embedded Boxes: Cutout should be ~20 mm larger than the box dimensions, with depth matching box thickness plus plastering. Ensure the box is level and plumb, with no vertical deviation exceeding 3 mm .
- Finishing: Apply anti-corrosive paint where the box contacts the wall. Ensure no gaps around the box edges for a snug fit .
Electrical Connections
- Fuse Installation: Connect screw fuses to intermediate contact terminals and load lines to threaded terminals to prevent electric shock during replacement. Porcelain fuses should be installed vertically .
- Switch and Load Wiring: Arrange wiring in loops from one point to another, ensuring each appliance can be controlled individually .
Safety Considerations
- Concealed wiring should only be installed in dry rooms unless using water-protected cables (IP x1 or higher), .
- Maintain proper spacing and avoid clustering pull and junction boxes in high-traffic areas .
- Ensure all conduits and boxes are securely fixed to prevent movement and potential hazards .
By following these steps, concealed wiring in household distribution boxes can be installed safely, efficiently, and in compliance with standard electrical practices, providing both protection and aesthetic appeal.
