New Articles
There are four new Articles in the 2020 NEC and they are listed below for the user's convenience.
(1) Article 242—Overvoltage Protection (CMP-10)
This new Aticle provides the general, installation, and connection requirements for overvoltage protection and overvoltage protective devices. A lot of the information contained in this Article was relocated from previous Articles 280 (Surge Arresters, Over 1000 Volts) and 285 (Surge-Protective Devices, 1000 Volts or Less). These requirements are more appropriately located immediately following Article 240 for overcurrent protection. The requirements are reformatted into a single Article for clarity and useability. Part II of the Article covers surge-protective devices (SPDs) permanently installed on premises wiring systems of not more than 1000 volts, nominal. Part III covers surge arresters permanently installed on premises wiring systems over 1000 volts, nominal.
(2) Article 311—Medium Voltage Conductors and Cable (CMP-6)
This Article will cover the use, installation, construction specifications and ampacities for medium voltage conductors and cable (Type MV). Medium voltage conductor and cable requirements that were previously found in Article 310 (Conductors or General Use) and 328 (Medium Voltage Cable) were consolidated into one Article to improve the usability of the Code. Article 310 received extensive reorganized to increase the usabilit of that Article. Users of the Code have encoutered difficulty over the years with the ampacity requirements of the Article becoming increasingly difficult to use, making Article 310 more difficult to use. Part of thie Article 310 reorganization included moving the Type MV cable requirements into new Article 311, which also includes moving the Type MV cable requirements out of Article 328 and deleting that Article entirely.
(3) Article 337—Type P Cable (CMP-6)
This new Article covers the use, installation, and construction specifications for up through 2000 volt Type P cable (armored and unarmored). Type P cable is defined as "a factory assembly of one or more insulated flexible tinned copper conductors, wth associated equipment grounding conductor(s), with or without a braided metallic armor and with an overall nonmetallic jacket." The definition permits single conductor Type P cables. Based on cable performance and requirements for some land-based operations (drilling rigs), Type P cable was originally proposed to be added to the 2020 NEC for hazardous area applications, but the final language after the Second Draft meetings does not restrict the use of Type P cable to hazardous locations. Type P cable is addressed by UL-1309 (Standard for Marine Shipyard Cable). This product standard describes Type P cable as flexible and rugged and highly suitable for petrochemical applications and oil and gas well drilling land based rigs because of its abilit to resist various chemicals, abrasives, and petroleum based additives as well as its ability to resist damage from vibration, shaking, and movement that occurs in many processes. This cable has a long successful history of more than four decades in installations in the most adverse conditions. With this cable, an equipment grounding conductor (EGC) that complies with 250.122, is required. It is not limited to an insulated conductor. The armor of this cable is not permitted as the EGC, as addressed in 337.116.
(4) Article 800—General Requirements for Communications Systems (CMP-16)
New Article 800 (General Requirements for Communications Systems) combines common requirements previoiusly found in Article 800 (now Article 805) for communication circuits, 820 for community antenna television and radio distribution systems, 830 for network-powered broadband communications systems and 840 for premises-powered broadband communications systems into a new "general" article that applies to all of these Articles unless modified by the forenamed Articles. This new Article will serve as a placeholder for redundant requirements throughout previous Articles 800 (now Article 805), 820, 830, and 840. It should be noted that previous Article 800 (Communications Circuits) is not Article 805.
For more detailed information on these Articles, see each individual Article in the 2020 NEC.
Chapter 1: Residential Calculations And Examples
Residential calculations are the most difficult to perform because the rules and regulations of the National Electrical Code are more restrictive than those for commercial and industrial facilities. The standard or optional calculation shall be permitted to be used to calculate the loads to size and select the elements for the feeder or service. The optional calculation seems to be the favorite method used by designers and electricians. This is true because once loads are calculated, it produces smaller VA or amps than the more complicated standard calculation. Therefore, smaller components are required in the electrical system and greater savings in wiring methods are achieved. The procedure for laying out residential calculations will be different in some ways from those used for commercial and industrial.
Test takers are finding that a test problem does not always consist of adding all of the loads together to determine the size service or feeder load for a dwelling unit. Instead, individual problems are asked, such as finding the small-appliance and laundry loads as illustrated in Figure 1-3 in this book.
Chapter 2: Commercial Calculations And Examples
Commercial facilities such as offices, banks, stores, and restaurants have diverse loads. These loads are classified as continuous or noncontinuous, or such loads may cycle on and off, allowing demand factors to be applied.
The procedure and manner in which the lighting, receptacle, and equipment loads are used in the electrical system determines how they are classified.
Loads shall be calculated based on the type of occupancy and the requirements of the equipment supplied. Either the standard or optional calculation is utilized to calculate the loads in volt-amps or amps to size the service equipment and associated elements.
Note: Section 220.12(B) in the NEC is utilized when a building is designed and constructed to comply with an energy code that is adopted by the local authority,
Chapter 3: Industrial Calculations And Examples
The National Electrical Code recognizes certain requirements for calculating loads for sizing and selecting elements of electrical systems used to supply power to industrial occupancies. According to NEC requirements, each service and feeder shall be calculated and sized with enough capacity to carry a load current that is not less than the sum of all branch circuits it supplies in the electrical system. These calculations vary, depending on the type of facility, and the size and nature of the total load served.
In any electrical system, the distribution system consists of the equipment and wiring methods used to carry power from the supply transformer to the service equipment’s overcurrent devices.
Distribution systems are used to carry power to lighting panelboards, power panelboards, switchboards, and motor control centers that house feeders and branch-circuit protective devices for supplying individual and multiple power loads. Adequate calculations will ensure that the elements of the system will provide the right amount of power at the right voltage to each distribution point.
