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The New Engineering Contract (NEC), or NEC Engineering and Construction Contract, is a formalised system created by the UK Institution of Civil Engineers that guides the drafting of documents on civil engineering, construction and maintenance projects for the purpose of obtaining tenders, awarding and administering contracts.
That creates a system whereby a city can best avoid lawsuits by adopting a single standard set of building code laws. This has led to the NEC becoming the de facto standard set of electrical requirements. [6] A licensed electrician will have spent years of apprenticeship studying and practicing the NEC requirements prior to obtaining their license.
The conduit may be coated to prevent corrosion by incidental contact with concrete. Aluminum conduit is generally lower cost than steel in addition to having a lower labor cost to install, since a length of aluminum conduit will have about one-third the weight of an equally-sized rigid steel conduit. [2]
It has cost and weight advantages over copper wires. Aluminum in power transmission and distribution applications is still the preferred wire material today. [3] In North American residential construction, aluminum wire was used for wiring entire houses for a short time from the 1960s to the mid-1970s during a period of high copper prices.
In commercial and industrial, unenclosed NM cable is often prohibited in certain areas or altogether (depending on what the building is used for and local/state building codes). Therefore, it is almost never used by commercial electrical contractors. Most wiring is put in non-flexible conduit, usually EMT because of its cost and durability.
The conduit methods were known to be of better quality, but cost significantly more than K&T. [2] In 1909, flexible armored cable cost about twice as much as K&T, and conduit cost about three times the price of K&T. [6] Knob and tube wiring persisted since it allowed owners to wire a building for electricity at lower cost.
By arranging wires on opposite sides of building structural members, some protection was afforded against short-circuits that can be caused by driving a nail into both conductors simultaneously. By the 1940s, the labor cost of installing two conductors rather than one cable resulted in a decline in new knob-and-tube installations.
Floor Level of an existing or proposed building or concrete pad FN or F/N: flag note, flagnote; find number: 1. Flagnote: A flagnote is a note that is called out in specific spots in the field of the drawing. It is numbered with a stylized flag symbol surrounding the number (or sometimes a delta symbol). A general note applies generally and is ...