Commercial & Industrial Wiring

This course will review the 2014 National Electrical Code requirement for the installation of commercial and industrial wiring systems and equipment. It is designed to assist commercial building inspectors and building science thermographers on the basics and understanding of the generally followed construction standards of installation which is prudent during the investigative stage of any property condition assessment or electrical system thermal infrared survey.

Topics covered will include branch circuits and feeders, services, overcurrent protection, grounding and bonding, wiring methods and materials, switchboards and panelboards, motors, motor circuits, and motor controllers, generators, transformers, and industrial machinery.

NACBI (The National Association of Commercial Building Inspectors and Thermographers™) is a U.S. and Canadian membership association dedicated to the training and advancement of Commercial Building Inspector and Thermographic Infrared Survey members.

The purpose of this training manual is to provide Commercial Building Inspectors and building science thermographers with a reference manual containing information pertinent to their profession using the 2014 NEC.

Section 1: Introduction to the NEC

1.1 Purpose of the NEC
1.2 What’s Covered in The NEC
1.3 What’s Not Covered in the NEC
1.4 NEC Code Arrangement

1.1 Purpose of the NEC
The NEC provides practical requirements for electrical systems and installations to safeguard persons and property.

The National Electrical Code (NEC) is a uniform code owned and maintained by the National Fire Protection Associations (NFPA). The first NECA® was adopted in 1897. The NEC is prepared by National Electrical Code “Code-Making” panels and updated every three years. It is used in both the United States and other countries and is the most widely adopted electrical standard in North America.

The purpose of the NEC is to protect the public from the hazards of shock and fire. It has helped dramatically in reducing the number of deaths from fire and electrocution. The NEC is a minimum Code and does not take into consideration future expansion or what is the most convenient or efficient installation.

The NEC is not a design or instructional manual and is not intended to teach untrained individuals on how to install electrical wiring.

Review Question Section 1.1

1. The purpose of the NEC is:

1.2 What’s Covered in The NEC

The NEC covers the installation of electrical systems in publicly owned buildings and structures. It also covers privately owned commercial building, industrial plants, and dwellings.

Outdoor installations such as carnivals, parking lot lights, and yards as well as Temporary installations for construction sites and holiday decorative lighting are covered by the NEC. As seen in the illustration, floating buildings and docks are also covered.

Determining whether or not the NEC covers facilities owned by a utility company is more complicated. Buildings and structures used for generating electricity like power plants, hydroelectric dams, and substations are not covered by the NEC. However, the NEC covers offices, warehouses, garages, machine shops, and recreational buildings owned by utilities. Parking lot lighting owned and maintained by utilities is not covered by the NEC.

Review Question Section 1.2

2. Which of the following electrical installations are covered by the NEC?

The NEC covers buildings on land and buildings that float.

1.3 What’s Not Covered in The NEC
The NEC applies to garages but not trucks or cars.

A number of installations are not covered by the National Electrical Code. For example, installations in ships, aircraft, automobiles, rail cars, signal and communication facilities are not covered by the NEC. Even though floating buildings are covered, watercraft are not.

The installation of equipment under the exclusive control of communication utilities such as telephone and CATV is not covered by the NEC. However, installation of signal and communication conductors and equipment in buildings and structures not owned by these utilities is covered. An example of equipment not covered by the NEC is a CATV booster used to boost the signal to CATV customers in rural areas.

Facilities of electric utilities used for generation, transmission or distribution of electricity are also exempt from the requirements of the NEC. For example, power plants used for generating electricity and utility substations are not covered. Utility installations in legally established easements or right of way are not covered. Utility installations that are covered by written agreements with public service commissions, utility commissions or other regulatory agencies are also not covered by the NEC.

Review Question Section 1.3

3. Which of the following electrical installations is not covered by the NEC?

1.4 NEC Code Arrangement

The NEC includes an introduction and nine chapters. The introduction explains the purpose of the NEC, what it applies to, how it is enforced, and how it is organized. Chapters 1-4 apply to installations in general while chapters 5-7 apply to certain types of occupancies, equipment or conditions such as hazardous locations, hospitals, mobile homes, signs, swimming pools, emergency systems and low voltage wiring. Chapter 8 covers Communications Systems. Chapter 9 includes various tables and Informative Annexes A-I.

The requirements in chapters 5-7 modify or add to the material in chapter 1.4. For example, section 725.3 states “Only those sections of Article 300 referenced in this article shall apply to Class 1, Class 2, and Class 3 circuits”. Because 300.17, 300.21 and 300.22 are the only sections of Article 300 that are mentioned in Article 725, those sections are the only ones that apply to article 725.

Chapters 1-7 do not apply to chapter 8 unless specifically mentioned in Chapter 8. For example, Section 800.3(B) requires communications circuits installed in plenums to comply with section 300.22(A).

Review Question Section 1.4

4. How many chapters does the National Electrical Code have?

The NEC is divided into 9 chapters that are outlined in section 90.3.