Ch.9 - Electrical and Communication Requirements

Delia Tacheny
Reading: The Codes Guidebook for Interiors
INT 324 - Building Codes

Keywords:

• National Electrical Code (NEC)
• Generation source
• Transmission system
• Distribution system
• Grounded 
• Structured Cabling

This week we are tackling the subject of electrical and communication. Most projects will require an electrical engineer or specialist, when it comes to planning and installing all of the electrical. However, as an interior designer, it's important to be able to communicate information regarding these topics, and be able to plan for types and location of outlets, fixtures, equipment, and appliances, especially in smaller scale projects. The NFPA 70, National Electrical Code (NEC) is the most widely used Electrical code in the United States. 

Electrical

A power system that provides electricity to buildings consists of three basic parts: the generation source, the transmission system, and the distribution system. The most common generation sources in the U.S. are hydroelectric power, nuclear, and fossil fuels. The transmission (or distribution) system consists of high-voltage lines stretching hundreds of miles, delivering power from the generation source to the local utility provider's substation. The distribution system then delivers high voltage power from the local distributor to the end user, who usually needs a transformer to step down the voltage to a usable amount. The utility distribution system ends at the point of delivery to the building, referred to as a service connection. 

The typical components of an electrical system include the electrical panel and cabling, receptacles, switches, and any additional devices used by the occupants -- all must be tested and labeled, usually by UL. 

There are three typical types of electrical panels in a building of which these are two of the primary ones: 

1. Service entrance (largest) - switchboard or panel board that distributes electricity to the rest of the building, and requires a regulated room to house the panel.
2. Branch panelboards - housed in smaller electrical rooms within each floor or tenant space.

Electricity is transmitted through cabling of which the main kinds are Romex, Armored Cable, Metal-clad cable, flat wire, or fiber optic cable. Often times, for safety purposes, electrical cabling is required to be enclosed in conduit or raceways. When electrical cabling is installed, the diameter of any passage hole cannot be more than 1/8inch larger than the diameter of the cable/conduit/etc., and if a rated assembly is penetrated, a fire-stop or smoke-stop must be used. The continued distribution of electricity is organized through circuits which feed various fixtures, outlets, appliances, etc. The NEC limits the amount of Amperage allowed in a single circuit. 

The three main types of electrical boxes are outlet boxes, switch boxes, and junction boxes. The outlets boxes can be wall/ floor mounted for electrical receptacles, or wall/ ceiling mounted for lighting fixtures. Wall outlets must be within accessible reach of 15" - 48" above the floor. Switch boxes are typically wall mounted and control the lighting fixture outlets. A junction box is used to tie/splice several wires together at various points, and are often located on or near the ceiling. 

All electrical systems must be grounded for safety, where a ground wire redirects live currents back to the source or the earth. Additional circuit interrupters are used in some cases as well: Ground Fault Circuit Interrupters (GFCI) wherever water is involved and Arc Fault Circuit Interrupters (AFCI) in most areas of residential dwelling units. 

Light fixtures are also part of the electrical requirements including regulations on type and location of fixtures, as well as the footcandles required. Additionally, it is important to understand that in addition to the standard electrical system, there are Emergency Power Systems and Standby Power Systems. 

Communication Systems

The type of cabling used for communication systems is called structured cabling, made up of backbone cabling and horizontal cabling. Backbone cabling carries the signals to the main distribution areas of the building or space, and horizontal cabling are the cables pulled to each workstation or outlet. Cabling for communication systems are considered low-voltage cabling in contrast to electrical cables. The most common types of cable/ connections are fiber optic cable, twisted-pair cable, coaxial cable, composite cable, circuit integrity cable, or wireless. 

Located in the basement or on the ground floor, every building will contain a central area where all the incoming communication services are connected to the buildings communication systems. These are the primary communication systems:

• Telecommunication (audio, visual, data)
• Television and Radio
• Alarm and Voice Communication 
• Audiovisual
• Security

Each one can be further explored in the Codes or this chapter. 

Source(s):

Kennon, Katherine E., and Sharon Koomen Harmon. “Ch.9: Electrical and Communication Requirements.” The Codes Guidebook for Interiors, John Wiley & Sons, Inc., Hoboken, NJ, 2022.