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For power circuits, the color-coding uses the same colors as residential construction, and adds the additional wires used for three-phase systems. Black, Red and Blue are used for hot wires and White is used as the neutral wire in a 120/208 V circuit. Brown, Orange and Yellow are used as hot wires and gray is used as the neutral wire in a 277/ ...
Wiring running through tubes, and turning a corner supported by a knob. Notice the direct splice with more modern (1950s-era) non-metallic–sheathed cable. This type of connection is forbidden by the National Electrical Code, and a junction box should have been used.
When used for plain old telephone service (POTS), the first wire is known as the tip or A-leg (U.K.) conductor, and is usually connected to the positive side of a direct current (DC) circuit, while the second wire is known as the ring lead or B-leg (U.K.), and is connected to the negative side of the circuit. Neither of these two sides of the ...
A somewhat similar system called "concentric wiring" was introduced in the United States around 1905. In this system, an insulated electrical wire was wrapped with copper tape which was then soldered, forming the grounded (return) conductor of the wiring system. The bare metal sheath, at earth potential, was considered safe to touch.
The three conductors are usually coloured red, black, and white. The white serves as a common neutral, while the red and black each feed, separately, the top and bottom hot sides of the receptacle. Typically such receptacles are supplied from two circuit breakers in which the handles of two poles are tied together for a common trip.
Household wiring does not usually use three-phase supplies and the clash only occurs in three-phase systems. Wiring to the old standard can be detected by use of a red wire. The new standard colour code does not use red. Where new wiring is mixed with old, cables must be clearly marked to prevent interchange of phase and neutral.
The 1915 textbook Practical Electric Wiring describes the construction of the Western Union splice; short tie and long tie. The short tie splice has it being formed after stripping the insulation from a pair of wires for several inches, each, crossing the wires left over right as shown in figure part A; then, a hooked cross (figure part B) is formed holding the crossing point of the two wires ...
If colored white, it typically may be used for splicing neutral wires in a device box, while leaving a pigtail free for connection to a device (such as a receptacle). If colored green, the assembly is intended to be used as a grounding pigtail, similar to the feedthrough twist-on wire connectors without a permanently-attached wire.