NEC Article 220 provides the methods and requirements for calculating the load for branch circuits, feeders, and services. These calculations ensure that electrical systems are designed to handle the expected electrical demand safely and efficiently. Here is a comprehensive overview of NEC Article 220, covering sections 220.1 to 220.87:

220.1 Scope

This section establishes the scope of Article 220, which covers the requirements for calculating branch-circuit, feeder, and service loads.

220.2 Calculation Methods

Provides general guidelines for calculating loads, emphasizing the importance of using accurate methods to ensure safety and reliability.

220.3 Application of Other Articles

This section references other NEC articles that provide additional requirements and guidelines for specific types of load calculations.

220.5 Calculations

• 220.5(A) Volt-Amperes: Specifies that calculations must be based on volt-amperes (VA).
• 220.5(B) Fractions of an Ampere: Provides rules for rounding calculations involving fractions of an ampere.

220.10 General Lighting

Specifies the general lighting load calculations for dwelling units and commercial buildings:

• 220.12 Lighting Load for Specified Occupancies: Lists the minimum unit loads for various types of occupancies.
• 220.14 Other Loads – All Occupancies: Provides guidelines for calculating additional loads in all types of occupancies.

220.16 Loads for Additions to Existing Installations

Specifies the method for calculating additional loads when adding new circuits to existing installations.

220.18 Maximum Loads

This section outlines the maximum permissible loads on branch circuits to ensure safe operation:

• 220.18(A) Continuous and Noncontinuous Loads: Specifies how to calculate loads that are continuous (operating for three hours or more) and noncontinuous.
• 220.18(B) Motor Loads: Provides guidelines for calculating motor loads.

220.40 General

Specifies that the calculation of feeder and service loads must consider all connected loads, including general lighting, appliances, and special equipment.

220.42 General Lighting

Provides methods for calculating the general lighting load for various types of occupancies:

• 220.42(A) Dwelling Units: Specifies the lighting load calculation method for dwelling units.
• 220.42(B) Non-Dwelling Units: Provides guidelines for calculating lighting loads in commercial and industrial buildings.

220.43 Show-Windows and Track Lighting

Outlines the requirements for calculating loads for show-windows and track lighting:

• 220.43(A) Show-Windows: Specifies the calculation method for show-window lighting loads.
• 220.43(B) Track Lighting: Provides guidelines for calculating loads for track lighting systems.

220.44 Receptacle Loads – Other Than Dwelling Units

Specifies the method for calculating receptacle loads in non-dwelling units, such as commercial and industrial buildings.

220.50 Motors

Provides guidelines for calculating motor loads, including allowances for starting currents and demand factors.

220.52 Small Appliance and Laundry Loads – Dwelling Unit

This section outlines the requirements for calculating small appliance and laundry loads in dwelling units:

• 220.52(A) Small Appliance Loads: Specifies the calculation method for small appliance loads in kitchens, dining rooms, and similar areas.
• 220.52(B) Laundry Loads: Provides guidelines for calculating laundry equipment loads.

220.54 Electric Clothes Dryers – Dwelling Unit

Specifies the calculation method for electric clothes dryer loads in dwelling units.

220.55 Electric Ranges and Other Cooking Appliances – Dwelling Unit

Outlines the requirements for calculating loads for electric ranges and other cooking appliances in dwelling units.

220.56 Kitchen Equipment – Other Than Dwelling Units

Provides guidelines for calculating loads for kitchen equipment in commercial and institutional kitchens.

220.60 Noncoincident Loads

Specifies how to calculate loads that do not operate simultaneously to ensure accurate demand calculations.

220.61 Feeder or Service Neutral Load

Outlines the requirements for calculating the neutral load for feeders and services, ensuring safe and reliable operation.

220.70 Optional Calculations – Dwelling Unit

Provides optional methods for calculating loads in dwelling units to allow for more flexibility in design.

220.80 Multiple Occupancy Buildings

Specifies the method for calculating loads for buildings with multiple occupancies, such as apartment buildings and shopping centers.

220.87 Determining Existing Loads

Provides guidelines for determining the existing loads on a system when making additions or modifications to ensure safe operation.

Conclusion

NEC Article 220 provides comprehensive guidelines for calculating the loads for branch circuits, feeders, and services. These calculations are essential for designing safe and reliable electrical systems that can handle the expected electrical demand.

For detailed information and further context, referring to the NEC Handbook and other resources provided by the NFPA is highly recommended.