Electrical engineers, inspectors and contractors, and the National Electrical Code (NEC), have dealt with nonlinear loads for many years. The issue arose in the late 1970s and early 1980s with the increased use of solid-state...
Recently, I received a phone call from an electrical contractor friend who was discussing with an electrical inspector the differences of branch circuits supplying swimming pool equipment versus swimming pool equipment feeder...
Electrical contractors are becoming more involved in the design, installation and servicing of solar photovoltaic (PV) systems for residential, commercial and industrial facilities. While this may be a sideline business for...
Last month’s article covered the general requirements in the National Electrical Code for audio signal processing, amplification and sound equipment in Article 640. One of the most common mistakes many electricians and...
When I was an electrical contractor, I tried to find a specialty where there was less competition and more profit than the normal building wiring. Many ECs doing electrical wiring for dwellings, commercial and industrial...
With the advent of power over ethernet in the 2017 National Electrical Code (NEC) , in Article 393 of the 2014 NEC covering low-voltage ceiling grid power, and other applications dealing with power-limited circuits, there...
Let’s assume a 120/208-volt (V), three-phase service was installed on a building a few years ago and the new owner of the building needs a standby generator for use during power outages. The electrical contractor installs a...
National Electrical Code (NEC) Panel 3 established the new Article 728 in the 2014 NEC. It deals with fire-resistive cabling systems, and it was marginally revised for the 2017 NEC . The article covers the installation of...
I have always been fascinated by cables and conductors—sometimes referred to as wires in the National Electrical Code (NEC) and other standards—and the insulation for these cables and conductors, as well as their multiple...
One of my passions, other than the National Electrical Code (NEC), has been fire alarm systems, as covered by NFPA 72, National Fire Alarm and Signaling Code. When I was a licensed electrical contractor in the Phoenix area in...
Both the National Electrical Code (NEC) and NFPA 70E, Standard for Electrical Safety in the Workplace, use the phrase “arcing current.” It is located in 240.87(B)(5) and (B)(6) in the NEC and in many places within NFPA 70E....
Can a manual transfer switch, a trapped key interlock system (commonly known as a Kirk Key system), an emergency automatic transfer switch and a permanently mounted generator be used at an industrial installation to provide...
Electrical systems age, usage increases and people upgrade their homes and offices. This combination is pushing many electrical systems to their limits. Enhancing a home or office’s electrical service requires an informed...
General requirements for conductor connections, terminations, splices and terminal temperatures are covered in 110.14 of the National Electrical Code (NEC). Since 1990, there have been some very substantial changes in 110.14...
I recently received an email from a homeowner who was installing a high-end media room and had questions about his home’s electrical system and the new circuits for the audio/video equipment. Before doing the installation,...
Transformer installations are common throughout residential, commercial and industrial applications. Most electricians, electrical contractors, electrical engineers and electrical inspectors are familiar with installation...
Each National Electrical Code (NEC) revision cycle seems to result in a multitude of changes in Article 210, Part III, which covers required lighting and receptacle outlets. There are so many changes in each new Code that...
Does the National Electrical Code (NEC) recognize reconditioned electrical equipment, and is such equipment safe? There are many different considerations in this question, and the acceptance of reconditioned electrical...
Two sections in the National Electrical Code (NEC) provide methods of calculating loads for existing installations. One deals exclusively with existing dwelling units, while the other deals with any existing dwellings,...
A friend recently sent me an email with this picture (right) of a manual fire alarm pull station mounted on the side of an electrical panelboard. My friend was inspecting the fire alarm system and was accompanied by the...
