🔌 Estimation of Load, Cable Size, Bill of Material and Cost
📋 1. Estimation of Load
Before starting any electrical installation, it is important to estimate the total load. This ensures that cables and protective devices are properly sized to handle the demand safely.
✅ How to Estimate Load:
- 👉 List all electrical appliances and their power ratings (Watts).
- 👉 Add up all the wattages to get the Total Connected Load.
- 👉 Apply a Demand Factor because all appliances may not run at the same time.
🧮 Example:
- Lights: 10 × 15W = 150W
- Fans: 5 × 70W = 350W
- Refrigerator: 200W
- Air Conditioner: 1500W
Total Connected Load = 150 + 350 + 200 + 1500 = 2200W or 2.2kW
Applying diversity (80%): 2.2kW × 0.8 = 1.76kW (maximum demand)
🔌 2. Cable Size Selection
Choosing the correct cable size is important to avoid overheating and ensure efficient power delivery.
✅ Factors to Consider:
- 🔸 Current to be carried (Amperes).
- 🔸 Length of cable (to check voltage drop).
- 🔸 Ambient temperature and installation conditions.
✅ Simple Calculation:
Current (I) = Power (W) / Voltage (V)
For 2.2kW at 230V:
I = 2200 ÷ 230 ≈ 9.56 Amps
Recommended Cable Size = 1.5 sq.mm copper wire (good for up to 10A load)
📝 3. Bill of Material (BOM)
The Bill of Material lists all components and materials required for the installation.
✅ Sample BOM:
| 📦 Item | 🔢 Quantity | 🛠️ Specification |
|---|---|---|
| Wires | 100 meters | 1.5 sq.mm copper PVC wire |
| Switches | 12 | 6A modular |
| Sockets | 6 | 6A universal type |
| MCB | 2 | 10A, Single pole |
| Distribution Board | 1 | 4 Way SPN DB |
| Earthing Rod | 1 | Copper Bonded |
| Conduit Pipes | 25 meters | PVC, 25mm diameter |
💰 4. Cost Estimation
Cost estimation includes the cost of materials, labor, and miscellaneous expenses.
✅ Typical Cost Distribution:
- 📦 Material Cost: Approx. ₹12,000
- 👷 Labor Cost: Approx. ₹4,000
- 🔧 Miscellaneous (installation tools, fittings): ₹1,000
- ➕ Contingency (5-10%): ₹1,000
Total Estimated Cost ≈ ₹18,000
🎯 Conclusion
Proper estimation of load, correct selection of cable size, a detailed bill of material, and accurate cost estimation help in safe, economical, and efficient electrical installation. 📈 Always remember to follow standard practices and safety rules! ⚡🔒