Understanding Electrical Load Calculations for MEP Projects

 Introduction

Electrical load calculation is a critical step in MEP design that ensures a building's electrical system is designed to handle the expected power demand efficiently. Proper load calculations help in preventing overload, ensuring energy efficiency, and meeting local regulations such as those set by Abu Dhabi Distribution Company (ADDC).

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1. What is Electrical Load Calculation?

Electrical load calculation is the process of determining the total power consumption of a building or a specific area to size circuit breakers, transformers, cables, DBs, FDBs, SMDBs, and MDBs appropriately.

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2. Steps for Electrical Load Calculation

Step 1: Identify the Loads

Classify all electrical loads in the project, such as:
✔ Lighting Load – Indoor and outdoor lighting
✔ Power Load – Sockets, appliances, industrial machines
✔ HVAC Load – Air conditioning units, chillers, fans
✔ Special Loads – Elevators, pumps, emergency systems

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Step 2: Calculate Individual Loads

The load is calculated using the formula:

$$\text{Power (W)} = \text{Voltage (V)} \times \text{Current (A)}$$

For example:

• A 100W LED light running at 230V will draw 0.43A.
• A 2-ton AC (2400W) running at 230V will draw 10.43A.

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Step 3: Apply Demand Factors

Different loads do not operate at full capacity at all times, so demand factors are applied based on guidelines like NEC (National Electrical Code) or ADDC regulations.

Example:

• Lighting Load Demand Factor = 100%
• Receptacle Load Demand Factor = 50% for non-continuous use

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Step 4: Determine the Total Connected Load

The total connected load is calculated by summing up all individual loads and applying their respective demand factors.

$$\text{Total Connected Load} = \sum (\text{Individual Load} \times \text{Demand Factor})$$

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Step 5: Sizing Circuit Breakers & Cables

After calculating the total load, circuit breakers and cables are selected based on safety margins and voltage drop calculations.

✔ Main Distribution Board (MDB) & SMDB Sizing – Based on total power requirement
✔ Cable Sizing – Based on current carrying capacity & voltage drop

For instance, if the total calculated load is 100 kW, you would size a 125A breaker with an appropriate cable size.

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3. Tools Used for Electrical Load Calculation

Some commonly used software for accurate calculations:
🔹 Dialux – For lighting load calculations
🔹 ETAP – For power system analysis
🔹 AutoCAD Electrical – For circuit and panel board design
🔹 Excel Sheets – For manual load scheduling

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4. Compliance with ADDC Standards

For MEP projects in Abu Dhabi, all electrical designs must be submitted for approval to Abu Dhabi Distribution Company (ADDC). Key compliance points include:
✔ Correct sizing of transformers, switchgear, and panels
✔ Compliance with voltage drop limits
✔ Use of approved materials and designs

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5. Conclusion

Electrical load calculation is a fundamental step in MEP design. A well-designed electrical system ensures efficiency, safety, and regulatory compliance. By following a structured approach and using the right tools, MEP engineers can optimize building power distribution systems effectively.

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What’s Next?
Interested in learning how to design a Single Line Diagram (SLD) for your project? Stay tuned for my next blog! 🚀

🔹 Do you have any questions about MEP electrical load calculations? Drop them in the comments below!