If there is one common thread throughout the electrical industry, it seems to be centered on grounding and bonding. Article 250 provides many of the requirements for grounding and bonding but is still difficult to understand.
This month's column concerns overcurrent protection for conductors in motor and controller circuits and overload protection for motors, subjects that many subscribers to our "Code Question of the Day" online feature have inquired about.
Contrary to popular electrical opinion, designated rules limit the number of conductors allowed within outlet, device, and junction boxes. Unfortunately, all too often, electricians remove junction box covers only to find the box crammed full of conductors.
Two similar installations have been proposed recently. The first is a proposed large hotel on a mountaintop at a distance of several miles from the nearest utility distribution line, and in a location subject to frequent lightning storms.
"In industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons will service the installation..." Think about how many times the National Electrical Code (NEC) begins a requirement with these words.
Is it acceptable to install nonmetallic sheathed cable (NM) exposed on a wall or in an attic, a basement, or a residential garage?
Where would physical protection of the NM cable be required, and where is physical protection of NM cable often used but not necessarily required?
The number and the content of "Code Question of the Day" submissions concerning the installation of nonmetallic sheathed cable suggests vast differences among, or lack of proper inspection of, electrical installations using Type NM cable as the wiring method.
CODE CITATIONS: Article 110-Requirements for Electrical Installations; Article 210-Branch Circuits; Article 220-Branch Circuit, Feeder, and Service Calculations; Article 230-Services; Article 250-Grounding; Article 310--Conductors for General Wiring; Article 430-Motors, Motor Circuits, and Controlle
It seemed like a simple run-of-the-mill question when first presented. So, let's run it again. QUESTION: "If I split-wire a receptacle by breaking off the tab provided on the receptacle, do I have to use a two-pole breaker to feed this receptacle?" The answer is a qualified yes.
One of the most confusing aspects of residential wiring is installing lighting fixtures in clothes closets. Therefore, the National Electrical Code (NEC) devotes one of its relatively few diagrams (Figure 410-8) to the subject of where lighting fixtures can be located in clothes closets.
CODE CITATIONS: Article 100-Definitions
Article 210-Branch Circuits;
Article 240-Overcurrent Protection;
Article 310-Conductors for General Wiring; and
Article 700-Emergency Systems
Type "2" Motor Starter Protection
Where installing Class 2 or Class 3 remote control, signaling, or power limited circuits in a raceway or where installing power-limited fire alarm circuits in a raceway, is it necessary to figure conduit fill?
Relocating the requirements for dedicated space below and above switchboards, panelboards, and motor control centers from Sec. 384-4 to Sec. 110-26 (110-16 in the '96 NEC logically combines these requirements with their related working space.