Estimation and Costing

Key principles for electrical installation planning, costing, and safety compliance.

💡 Estimation of Lighting Scheme

Determine total lumen required based on room size and usage.
Use formula: Total lumens = Area × Illumination Level
Select suitable lamps and calculate number of fittings needed.
Account for utilization factor and maintenance factor.
Prepare wiring layout and select suitable switchgear and control devices.

💡 Estimation of Electric Installation for Machines

Determine load and power rating of each machine.
Select correct cable size considering current and distance.
Include motor starter, isolator, fuses, and contactors as per requirement.
Plan earthing and protection devices (like MCB/ELCB).
Prepare single-line diagram (SLD) for clarity.

💡 Relevant IE (Indian Electricity) Rules

IE Rule 29: Earthing of installations.
IE Rule 46: Inspection and testing before connection.
IE Rule 61: Earth leakage protection for installations above 5 kW.
IE Rule 88: Earthing of neutral conductor.
All installations should be as per IS:732 (Code of Practice).

💡 Earthing Practices

Pipe Earthing: Common method using GI pipe and salt/charcoal filling.
Plate Earthing: GI/Copper plate used; effective for industrial loads.
Earth resistance should be less than 5 ohms for safety.
Earthing is essential for protection against leakage, faults, and lightning.

📘 Example Estimation

Room size: 10×10 ft, Illumination level: 300 lux
Total lumens required = 9.3 m² × 300 = 2790 lumens
If one LED bulb gives 900 lumens, total = 2790 / 900 = 3.1 ≈ 4 bulbs
Install: 4 LED bulbs with switch control and 1 MCB for safety