Wiring diagram

A wiring diagram is a simplified conventional pictorial representation of an electrical circuit. It shows the components of the circuit as simplified shapes, and the power and signal connections between the devices. A wiring diagram usually gives more information about the relative position and arrangement of devices and terminals on the devices, as an aid in construction the device. This is unlike a schematic diagram where the arrangement of the components interconnections on the diagram does not correspond to their physical locations in the finished device. A pictorial diagram would show more detail of the physical appearance, whereas a wiring diagram uses a more symbolic notation to emphasize interconnections over physical appearance.

A wiring diagram is used to troubleshoot problems and to make sure that all the connections have been made and that everything is present.

Architectural wiring diagrams

Architectural wiring diagrams show the approximate locations and interconnections of receptacles, lighting, and permanent electrical services in a building. Interconnecting wire routes may be shown approximately, where particuular receptacles or fixtures must be on a common circuit.

Wiring diagrams use standard symbols for wiring devices, usually different from those used on schematic diagrams. The electrical symbols not only show where something is to be installed, but also what type of device is being installed. For example, a surface ceiling light is shown by one symbol, a recessed ceiling light has a different symbol, and a surface fluorescent light has another symbol. Each type of switch has a different symbol and so do the various outlets. There are symbols that show the location of smoke detectors, the doorbell chime, and thermostat. On large projects symbols may be numbered to show, for example, the panel board and circuit to which the device connects, and also to identify which of several types of fixture are to be installed at that location.

A set of wiring diagrams may be required by the electrical inspection authority to approve connection of the residence to the public electrical supply system.

Wiring diagrams will also include panel schedules for circuit breaker panelboards, and riser diagrams for special services such as fire alarm or closed circuit television or other special services.

Electrical wiring

Electrical wiring in general refers to insulated conductors used to carry electricity, and associated devices. This article describes general aspects of electrical wiring as used to provide power in buildings and structures, commonly referred to as building wiring. This article is intended to describe common features of electrical wiring that should apply worldwide.

Wiring methods
Materials for wiring interior electrical systems in buildings vary depending on:

Intended use and amount of power demand on the circuit
Type of occupancy and size of the building
National and local regulations
Environment in which the wiring must operate.

Wiring systems in a single family home or duplex, for example, are simple, with relatively low power requirements, infrequent changes to the building structure and layout, usually with dry, moderate temperature, and noncorrosive environmental conditions. In a light commercial environment, more frequent wiring changes can be expected, large apparatus may be installed, and special conditions of heat or moisture may apply. Heavy industries have more demanding wiring requirements, such as very large currents and higher voltages, frequent changes of equipment layout, corrosive, or wet or explosive atmospheres. In facilities that handle flammable gases or liquids, special rules may govern the installation and wiring of electrical equipment in hazardous areas.

Early wiring methods

The very first interior power wiring systems used conductors that were bare or covered with cloth, which were secured by staples to the framing of the building or on running boards. Where conductors went through walls, they were protected with cloth tape. Splices were done similarly to telegraph connections, and soldered for security. Underground conductors were insulated with wrappings of cloth tape soaked in pitch, and laid in wooden troughs which were then buried. Such wiring systems were unsatisfactory because of the danger of electrocution and fire and the high labor cost for such installations.

Knob and tube

single conductors were run through cavities between the structural members in walls and ceilings, with ceramic tubes forming protective channels through joists and ceramic knobs attached to the structural members to provide air between the wire and the lumber and to support the wires. Since air was free to circulate over the wires, smaller conductors could be used than required in cables. 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.

Other historical wiring methods
Other methods of securing wiring that are now obsolete include:

Re-use of existing gas pipes for electric lighting. Insulated conductors were pulled into the pipes feeding gas lamps.
Wood moldings with grooves cut for single conductor wires, covered by a wooden cap strip. These were prohibited in North American electrical codes by 1928. Wooden molding was also used to some degree in England, but was never permitted by German and Austrian rules.
Metal molding systems, with a flattened oval section consisting of a base strip and a snap-on cap channel, were more costly than open wiring or wooden molding. Similar systems are still available today.

A system of flexible twin cords supported by glass or porcelain buttons was used near the turn of the 20th century in Europe, but was soon replaced by other methods.
During the first years of the 20th century various patented forms of wiring system such as Bergman and Peschel tubing were used to protect wiring; these used very thin fiber tubes or metal tubes which were also used as return conductors.

In Austria, wires were concealed by embedding a rubber tube in a groove in the wall, plastering over it and then removing the tube and pulling in wires in the cavity.

What is a Parallel Circuit?

A parallel circuit is one of the two basic types of electric circuit that can be found in electrical devices. "Circuit" refers to the total path of an electric current, or flow of electrical energy, and includes devices such as resistors, which control the flow of voltage, or difference in electrical charge, and capacitors, which store electrical charge. Circuits fall into one of two categories: series or parallel. In a series circuit, all the components of the circuit are lined up in a single path so that the current flows through each component in order.

In a parallel circuit, however, there are multiple pathways between the circuit’s beginning and end. As a result, since the current has more than one route to take, the circuit can still function if one path fails. This makes parallel circuits much more fail-resistant than series circuits which is why parallel circuits are common in everyday applications, such as household wiring. Regardless of how many different paths the circuit has, the total voltage stays the same, and all components of the circuit share the same common points. This set of common points is known as electrically common points. Every parallel circuit has two sets of them.

One thing to consider about parallel circuits is the current load that they carry. When a circuit has multiple paths for current, the circuit's total effective resistance drops. Since the voltage is equal to the current multiplied by the resistance — known as Ohm’s law, named for German physicist Georg Ohm — and the voltage does not change, this means the current has to increase. Thus, the more paths that a circuit has, the greater the current flow across each path will effectively become. This can lead to damage to the circuit or external equipment, which is why excessive use of outlet extenders or multi-plug inserts is considered hazardous. Parallel circuits are found in virtually all complex electrical devices. Many devices use both series and parallel circuits in conjoined and stand-alone configurations.

Another aspect of parallel circuits to keep in mind is that such circuits must be measured differently than series circuits. For example, when testing a parallel circuit using a voltmeter or multimeter, which tests multiple measurements, the multimeter must be connected in parallel to properly measure the voltage. Multiple branches means the load is distributed over more than one path, and measuring only one path will not present the full picture. If this isn’t done correctly, the measurement will be faulty, and the circuit may incorrectly be judged defective.

What Is an Electrical Circuit?

An electrical circuit is a closed loop formed by a power source, wires, a fuse, a load, and a switch. When the switch is turned on, the electricalelectricalelectrical circuit is complete and current flows from the negative terminal of the power source, through the wire to the load, to the positive terminal. Any device that consumes the energy flowing through a circuit and converts that energy into work is called a load. A light bulb is one example of a load; it consumes the electricity from a circuit and converts it into work — heat and light.

There are three types of circuits: series circuits, parallel circuits, and series-parallel circuits. A series circuit is the simplest because it has only one possible path that the electrical current may flow. If the electrical circuit is broken, none of the load devices will work. A parallel circuit has more than one path, so if one of the paths is broken, the other paths will continue to work.

A series-parallel circuit attaches some of the loads to a series circuit and others to parallel circuits. If the series circuit breaks, none of the loads will function. If one of the parallel circuits breaks, however, that parallel circuit and the series circuit will stop working, but the other parallel circuits will continue to work.

Many "laws" apply to electrical circuits, but Ohm's Law is probably the most well known. To understand Ohm's Law, it's important to understand the concepts of current, voltage, and resistance. Current is the flow of an electric charge. Voltage, or electrical potential difference, is the force that drives the current in one direction. Resistance is the opposition of an object to having current pass through it.

Ohm's Law states that an electrical circuit's current is directly proportional to its voltage and inversely proportional to its resistance. So, if voltage increases, for example, the current will also increase, and if resistance increases, current decreases. The formula for Ohm's Law is E = I x R, where E = voltage in volts, I = current in amperes, and R = resistance in ohms.

Source voltage is another important concept in electrical circuits. It refers to the amount of voltage that is applied to the circuit and is produced by the power source. Source voltage is affected by the amount of resistance within the electrical circuit and affects the amount of current. The current is affected by both voltage and resistance. Resistance is not affected by voltage or current, but it affects both voltage and current.