National Electrical Code Articles and Information

All answers are from Article 100.

1.   No. “Ampacity” is the current a conductor can carry continuously without exceeding its temperature rating. A given conductor may have different ampacities, depending on the application. Refer to the various tables in Chapter 3.

2.   Being "approved" isn't directly related to having a UL label. This is a common point of confusion. UL is just one of several testing agencies. A listing with one of these agencies is a factor the AHJ considers for granting approval. Also, the AHJ approves methods and materials. A testing agency merely lists the product as meeting certain safety or performance criteria for a given use.

3.   The NEC uses “AHJ” is a general sense. Where public safety is primary, the AHJ is an official having statutory authority--for example, the local city engineer. For insurance purposes, the AHJ can be anyone authorized by the insurance company to hold that role. In government installations, a commanding officer or departmental official may be the AHJ. To an electrical crew, the project manager may be the AHJ for all practical purposes. There is no hard and fast rule about "which" AHJ has "final say." You have to work out any differences with all parties that have authority over the project.

4.   The NEC defines "bathroom" as an area that includes a basin, toilet, tub, shower, or any combination thereof. And it may not be a room, per se. It only has to be an area. That is, a place that exists. Don't try to read between the lines. Before you finalize the design, discuss any questions with the AHJ. Otherwise, you may be ripping out finished construction and doing things over.

5.   Bonding and grounding do not serve the same purpose. Unfortunately, the NEC misapplies the term "grounding" (as defined in Article 100) throughout. This is one reason why our Grounding Courses are so popular. And so badly needed in the industry.

Grounding involves connecting something to the earth. This has benefits for lightning protection. It does nothing for power quality or other benefits commonly attributed to it. Bonding is the permanent joining of metallic parts to form an electrically conductive path that ensures electrical continuity and the capacity to conduct safely any current likely to be imposed. It eliminates differences in potential between non-current carrying conductors.

6.   A bonding jumper connects metal parts and creates part of the path back to the source or puts the parts at the same potential. An equipment bonding jumper electrically connects two or more portions of the equipment grounding conductor and puts them at the same potential. The main bonding jumper in a given installation electrically connects the grounded circuit conductor and the equipment grounding conductor at the service entrance. Article 250 prescribes how to make all these connections so they are reliable.

7.   In the hierarchy of circuits, you have service, feeder, and branch--in that order. The NEC definition is a bit stuffy, but you get the idea. There are different types of branch circuits, and when you read through what they are, that idea you just got becomes more clear.

8.   An appliance branch circuit supplies receptacles for appliances, only. If you want to supply room lighting or convenience outlets, you have to use another circuit. An individual branch circuit supplies a single receptacle. A general-purpose branch circuit supplies two or more receptacles.

9.   It's basically a wiring arrangement where two or more conductors share a neutral. You'll find the installation requirements in 210.4.

10.  Each addition might be a separate building under the NEC, or it might not. You have "building" when the structure stands alone or is cut off from adjoining structures by firewalls (and all openings protected by fire doors). You don't have a "building" simply because someone put up a wall between two large rooms built at different times.