When it comes to commercial electrical load calculations, it's crucial to ensure that you have the right size branch-circuit conductors and overcurrent protection. In this article, we'll explore the different requirements for various types of equipment and provide you with the necessary information to make accurate calculations.

Electric Heat

When sizing branch-circuit conductors and overcurrent protection for electric heating, it's important to consider the total heating load, including blower motors. The conductors and protection devices should be at least 125% of the total heating load. Additionally, the feeder or service demand load for electric heating equipment should be calculated at 100% of the total heating load.

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Kitchen Equipment

For commercial kitchen equipment, it's essential to size the branch-circuit conductors and overcurrent protection based on the appliance nameplate rating. If the equipment has thermostatic control or intermittent use, you should apply the demand factors from Table 220.20 to the total connected kitchen equipment load. Keep in mind that the feeder or service demand load should not be less than the sum of the two largest appliance loads. It's worth noting that the demand factors from Table 220.20 do not apply to space-heating, ventilating, or air-conditioning equipment.

Laundry Equipment

When sizing circuits for laundry equipment, you can assume that these circuits are not continuous loads. The circuits should be sized according to the appliance nameplate rating. In most cases, commercial laundry circuits are rated at 1,500VA unless stated otherwise in the project drawings or exam question.

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Lighting

The National Electrical Code (NEC) requires a minimum load per square foot for general lighting, depending on the type of occupancy. For guestrooms of hotels, motels, hospitals, and storage warehouses, you can apply the general lighting demand factors from Table 220.11. However, for commercial occupancies other than these, the general lighting load is considered continuous and should be calculated at 125% of the load listed in Table 220.3(A).

Receptacles

Calculating receptacle loads depends on the specific application and has separate requirements according to the NEC.

Multi-Outlet Receptacle Assembly

For service calculations, each 5 feet or less of a multi-outlet receptacle assembly should be considered as 180VA. If you expect the assembly to power multiple appliances simultaneously, each foot or less can be considered as 180VA for service calculations. Generally, a multi-outlet receptacle assembly is not a continuous load.

Receptacle VA Load

Each commercial or industrial general-use receptacle outlet should have a minimum load of 180VA per strap. Receptacles are typically not considered continuous loads.

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Number of Receptacles Permitted on a Circuit

The maximum number of receptacle outlets permitted on a commercial or industrial circuit depends on the circuit ampacity. To calculate the allowed number of receptacles, divide the VA rating of the circuit by 180VA for each receptacle strap.

Frequently Asked Questions

1. What is the minimum load requirement for general lighting in commercial occupancies other than guestrooms?

For commercial occupancies other than guestrooms of motels, hotels, hospitals, and storage warehouses, the general lighting load should be calculated at 125% of the load listed in Table 220.3(A).

2. Are commercial laundry circuits considered continuous loads?

No, commercial laundry circuits are typically not considered continuous loads. They are usually rated at 1,500VA unless specified otherwise.

3. How should branch-circuit conductors and overcurrent protection be sized for electric heating?

Branch-circuit conductors and overcurrent protection for electric heating should be sized at 125% of the total heating load, including blower motors.

4. What is the minimum load requirement for each commercial or industrial general-use receptacle outlet?

The minimum load requirement for each commercial or industrial general-use receptacle outlet is 180VA per strap.

5. How can I calculate the maximum number of receptacle outlets permitted on a circuit?

To calculate the maximum number of receptacle outlets permitted on a circuit, divide the VA rating of the circuit by 180VA for each receptacle strap.

In conclusion, accurately calculating the electrical load for commercial applications is crucial to ensure the safety and efficiency of the electrical system. By following the guidelines mentioned in this article, you can make informed decisions and comply with the necessary requirements.