Underwriter's knot | |
---|---|
Names | Underwriter's knot, Two-strand wall knot |
Category | Stopper |
Related | wall knot, crown knot |
Typical use | electrical |
Caveat | Note that the colors in this depiction do not match current practises in either the UK or the US, nor is this cable in keeping with current safety standards for electrical installations |
ABoK | #237, #775 |
The underwriter's knot is used in electrical wiring as strain relief to prevent a cable from being pulled from electrical terminals when the cable is yanked. [1]
Clifford Ashley listed it as an electrician's knot in 1944. He suggested it be used "where rough treatment is expected" and described it as a two-strand wall knot. [2]
The name may come from its use by fire underwriters, who understood its importance in electrocution and fire prevention. [3]
The knot is typically used as a stopper knot where a lamp or appliance cord passes through a hole or slot of a plug or socket. Its purpose is to "reduce strain on the screw terminal connections—where the metal parts of the wires connect to the socket or plug—and prevent the wires from pulling free." [4]
A whipping knot or whipping is a binding of marline twine or whipcord around the end of a rope to prevent its natural tendency to fray.
Components of an electrical circuit are electrically connected if an electric current can run between them through an electrical conductor. An electrical connector is an electromechanical device used to create an electrical connection between parts of an electrical circuit, or between different electrical circuits, thereby joining them into a larger circuit.
A grief knot is a knot which combines the features of a granny knot and a thief knot, producing a result which is not generally useful for working purposes. The word grief does not carry its usual meaning but is a portmanteau of granny and thief.
A power cord, line cord, or mains cable is an electrical cable that temporarily connects an appliance to the mains electricity supply via a wall socket or extension cord. The terms are generally used for cables using a power plug to connect to a single-phase alternating current power source at the local line voltage. The terms power cable, mains lead, flex or kettle lead are also used. A lamp cord is a light-weight, ungrounded, single-insulated two-wire cord used for small loads such as a table or floor lamp.
A grommet is a ring or edge strip inserted into a hole through thin material, typically a sheet of textile fabric, sheet metal or composite of carbon fiber, wood or honeycomb. Grommets are generally flared or collared on each side to keep them in place, and are often made of metal, plastic, or rubber. They may be used to prevent tearing or abrasion of the pierced material or protection from abrasion of the insulation on the wire, cable, line being routed through the penetration, and to cover sharp edges of the piercing, or all of the above.
A power strip is a block of electrical sockets that attaches to the end of a flexible cable, allowing multiple electrical devices to be powered from a single electrical socket. Power strips are often used when many electrical devices are in proximity, such as for audio, video, computer systems, appliances, power tools, and lighting. Power strips often include a circuit breaker to interrupt the electric current in case of an overload or a short circuit. Some power strips provide protection against electrical power surges. Typical housing styles include strip, rack-mount, under-monitor and direct plug-in.
Electrical wiring in North America follows the regulations and standards applicable at the installation location. It is also designed to provide proper function, and is also influenced by history and traditions of the location installation.
A stopper knot is a knot that creates a fixed thicker point on an otherwise-uniform thickness rope for the purpose of preventing the rope, at that point, from slipping through a narrow passage, such as a hole in a block. To pass a rope through a block, or hole, is to reeve it. To pull it out is to unreeve it. Stopper knots prevent the rope from unreeving on its own.
In electricity supply design, a ring circuit is an electrical wiring technique in which sockets and the distribution point are connected in a ring. It is contrasted with the usual radial circuit, in which sockets and the distribution point are connected in a line with the distribution point at one end.
In electrical and mechanical trades and manufacturing, each half of a pair of mating connectors or fasteners is conventionally assigned the designation male or female. The female connector is generally a receptacle that receives and holds the male connector. Alternative terminology such as plug and socket or jack are sometimes used, particularly for electrical connectors.
Electrical wiring in the United Kingdom is commonly understood to be an electrical installation for operation by end users within domestic, commercial, industrial, and other buildings, and also in special installations and locations, such as marinas or caravan parks. It does not normally cover the transmission or distribution of electricity to them.
An extension cord (US), extension cable, power extender, drop cord, or extension lead (UK) is a length of flexible electrical power cable (flex) with a plug on one end and one or more sockets on the other end. The term usually refers to mains extensions but is also used to refer to extensions for other types of cabling. If the plug and power outlet are of different types, the term "adapter cord" may be used. Most extension cords range from around 2 to 30 feet in length although they are made up to 300 feet (91.44 m) in length.
Knob-and-tube wiring is an early standardized method of electrical wiring in buildings, in common use in North America from about 1880 to the 1930s. It consisted of single-insulated copper conductors run within wall or ceiling cavities, passing through joist and stud drill-holes via protective porcelain insulating tubes, and supported along their length on nailed-down porcelain knob insulators. Where conductors entered a wiring device such as a lamp or switch, or were pulled into a wall, they were protected by flexible cloth insulating sleeving called loom. The first insulation was asphalt-saturated cotton cloth, then rubber became common. Wire splices in such installations were twisted together for good mechanical strength, then soldered and wrapped with rubber insulating tape and friction tape, or made inside metal junction boxes.
NEMA connectors are power plugs and sockets used for AC mains electricity in North America and other countries that use the standards set by the US National Electrical Manufacturers Association. NEMA wiring devices are made in current ratings from 15 to 60 amperes (A), with voltage ratings from 125 to 600 volts (V). Different combinations of contact blade widths, shapes, orientations, and dimensions create non-interchangeable connectors that are unique for each combination of voltage, electric current carrying capacity, and grounding system.
A modular connector is a type of electrical connector for cords and cables of electronic devices and appliances, such as in computer networking, telecommunication equipment, and audio headsets.
Cable management refers to management of electrical or optical cable in a cabinet or an installation. The term is used for products, workmanship or planning. Cables can easily become tangled, making them difficult to work with, sometimes resulting in devices accidentally becoming unplugged as one attempts to move a cable. Such cases are known as "cable spaghetti", and any kind of problem diagnosis and future updates to such enclosures could be very difficult.
A coiling or coil is a curve, helix, or spiral used for storing rope or cable in compact and reliable yet easily attainable form. They are often discussed with knots.
Rope are often coiled and hung up in lofts for storage. They are also hung over stakes in farm wagons and on hooks in moving vans, fire apparatus and linesmen's repair trucks. For such active storage coils must be well made.
MC4 connectors are single-contact electrical connectors commonly used for connecting solar panels. The MC in MC4 stands for the manufacturer Multi-Contact and the 4 for the 4 mm diameter contact pin. MC4s allow strings of panels to be easily constructed by pushing the compatible connectors from adjacent panels together by hand, but require a tool to disconnect them to ensure they do not accidentally disconnect when the cables are pulled. The National Electric Code (NEC) and the UL6703 standard for PV connectors specify that connectors have to be from the same type and brand to avoid the dangers of cross-mating. In addition, IEC 62548 ‘design requirements for PV Systems' require PV connectors to be of the same origin. Originally rated for 600V, newer versions of the MC4 connector are rated at 1500V, which allows longer series strings to be created.
Solarlok is a largely obsolete electrical connector used to connect solar panels together. Solarlok was introduced by Tyco International in order to meet new National Electrical Code (NEC) standards that required panel connectors to lock together and only be separated again using a tool. Solarlok became very common in the United States where the code first came into effect, but had varying degrees of market success outside the US. Due to the connector only being available from Tyco, the connectors are almost always referred to simply as Tyco connectors.
A towing sock or wire rope puller or wire pulling grip is a device that connects to the end of a cable, such as a power cable, in order to pull it through a tube or tunnel. It works by tightening around the cable when pulled, in the same manner as a Chinese finger trap. The towing sock is tubular and made of braided cable, open at one end and closed at the other where it connects to a tow line using an eye splice.