Understanding Commercial Fitout Power Load Calculations - Lceted -lceted LCETED INSTITUTE FOR CIVIL ENGINEERS

## Jun 19, 2024

Commercial fitout power load calculations are a critical component of planning and designing any commercial space. These calculations ensure that the electrical infrastructure is capable of supporting the intended use of the space, providing both safety and efficiency. Here’s an overview of how these calculations are typically performed.

Key Components of Power Load Calculations

• Unit Load: Each piece of equipment or electrical fixture has a specified unit load, typically measured in watts (W).
• Quantity: The number of each type of equipment or fixture.
• Total Load: Multiply the unit load by the quantity and convert the result to kilowatts (KW) by dividing by 1000.
2. Diversity Factor:
• The diversity factor accounts for the likelihood that not all equipment will be operating at full capacity simultaneously. This factor reduces the total load to a more realistic value, reflecting actual usage patterns.
3. Power Factor:
• Most commercial electrical systems operate with a power factor less than 1 (typically around 0.9). The power factor accounts for the inefficiency of electrical equipment and is used to adjust the maximum demand load accordingly.
4. Maximum Demand Calculation:
• Without Power Factor: Multiply the total load by the diversity factor.
• With Power Factor: Divide the maximum demand (without power factor) by the power factor to get the adjusted maximum demand.
5. Maximum Demand Amps:
• Convert the maximum demand in KW to amps, considering the voltage and type of electrical system (typically three-phase power systems in commercial settings).

• List all electrical equipment and fixtures, including HVAC systems, lighting, workstations, and any specialized equipment.
• For each item, multiply the unit load by the quantity to get the total load in watts. Convert this to kilowatts by dividing by 1000.
3. Apply Diversity Factor:
• Apply an appropriate diversity factor to the total load. For example, if the total calculated load is 100 KW and the diversity factor is 0.8, the maximum demand would be 80 KW.
• Divide the maximum demand by the power factor (e.g., 0.9) to account for inefficiencies. This gives the true maximum demand in KW.
5. Convert to Amps:
• Use the formula Amps = (KW×1000)/(Voltage×√3) to convert the maximum demand in KW to amps, assuming a three-phase power system.

Practical Example

Imagine a commercial office fitout with the following requirements:

• 20 workstations: Each requiring 200 W.
• Lighting: Total of 5000 W.
• Air Conditioning: Total of 15000 W.
• Diversity Factor: 0.8 for workstations and lighting, 1.0 for air conditioning.
• Power Factor: 0.9.

Step-by-Step Calculation:

• Workstations: 20×200=4000 W or 4 KW.
• Lighting: 5000 W or 5 KW.
• Air Conditioning: 15000 W or 15 KW.
• Total: 4+5+15=24 KW.
2. Apply Diversity Factor:
• Workstations and Lighting: (4+5) × 0.8=7.2 KW.
• Air Conditioning: 15×1.0=15 KW.
• Combined Maximum Demand: 7.2+15=22.2 KW.
• 22.2/0.9=24.67 KW.
4. Convert to Amps:
• Assuming a 415V three-phase system:
• Amps = (24.67×1000)/(415×√3) = 34.4

This example illustrates how to methodically calculate the electrical load requirements for a commercial fitout, ensuring that the electrical infrastructure can handle the anticipated load while accounting for practical usage patterns and system inefficiencies. Properly performed calculations are essential for designing safe, efficient, and effective commercial spaces.

Diversity Factor Table

The diversity factor accounts for the probability that not all electrical devices will be operating at their maximum load simultaneously. This factor reduces the overall load to a more practical estimate of the power demand.

 Equipment/Area Diversity Factor Office Workstations 0.8 General Lighting 0.8 HVAC Systems 1.0 Server Rooms 1.0 Kitchen Appliances 0.7 Meeting Rooms 0.9 Miscellaneous Equipment 0.8

Power Factor Table

The power factor is a measure of how effectively electrical power is being used by a system. It is a ratio of the real power that is used to do work to the apparent power that is supplied to the circuit. In commercial settings, power factors typically range from 0.8 to 0.95.

 Equipment/Area Power Factor Office Equipment 0.9 General Lighting 0.95 HVAC Systems 0.85 Industrial Equipment 0.8 Server Rooms 0.95 Kitchen Appliances 0.85 Miscellaneous Equipment 0.9

By incorporating these diversity and power factors into your calculations, you can ensure that your commercial fitout is designed to be both efficient and reliable. Proper planning and accurate calculations help avoid overloading circuits and ensure the safety and functionality of the space.