Electrical Glossary
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- Double insulated symbol, indicates an appliance that does not need to be earthed due to extra precautions against shock. Such appliances are not necessary double insulated, despite the technically inaccurate name that would appear to imply they are.
- 2-way switching
- A method of wiring switches so that a lamp can be turned on or off from more than one switch.
- Arc
- electrical conduction across insulation breakdown, often through air.
- Ashathene
- An obsolete plastic cable, a precursor of pvc. It lasts well, and is usually in good condition.
- Ballast
- Current control device used to run a fluorescent tube or other discharge lamp.
- BC
- Bayonet Cap, most popular type of lightbulb connection.
- Bipin
- 2 pin connection used on fluorescent tubes & halogen lamps.
- Cable
- CablesElectrical wire not intended for regular flexing. Has solid single core copper conductors. see also flex.
- Cable clips
- Clips that hold cable in place. Usually a plastic clip fixed in place with a small masonry nail, but other types also exist.
- CFL
- Compact Fluorescent Lamp. Energy saving lamp used in place of filament lamps.
- Chocolate block, choc block
- screw connector strip for mains cables.
- Circline
- circular fluorescent tube
- Contactor
- Relay (electrical)
- CPC
- Circuit Protective Conductor, earth conductor, earth wire.
- Crossover Switch
- Type of switch used only in 3 or more way switching.
- CU
- Consumer Unit. Formerly fusebox.
- Dimmer
- device for reducing the efficiency of filament bulbs.
- Discharge Lighting
- Lighting based on the principle of an arc. This includes fluorescent lights, sodium & mercury lights, and metal halide.
- Discrimination
Ensuring that when a protective device clears a fault, as few circuits as possible (ideally only the affected circuit) are disconnected. In the case of cascaded protective devices such as MCBs or Fuses, there must be sufficient difference in their trip rating such that only one one nearest the fault trips. (with cascaded RCDs discrimination is usually achieved by have devices with progressively faster response times as you move further from the circuits origin).
- Earth
- Electrical connection to earth / ground.
- Earth leakage
- the flow of mains current to earth, sometimes via a human. Earth current is often fault current, though not always.
- Earth wire
- electrical wire connected to earth
- ELCB
- Device to cut electrical power in the event of certain earth leakage faults. There are 2 different types of ELCB, current operated (aka RCD) and voltage operated. Now superceded by RCDs, the designation 'ELCB' indicates an old device.
- Electrocution
- Death by electric shock.
- Equipotential bonding
- ES
- Edison Screw. The most common size of screw-in lightbulb base. See also SES, MES
- Filament lamp
- Traditional light bulb containing a white hot filament. See also GLS.
- Fluorescent lamp
- A highly energy efficient type of lighting.
- Fuse
- Thin piece of wire which melts when excess current is passed, thus breaking the circuit. A fuse's rated current is the current it will pass indefinitely, not the current at which it fuses, which is significantly higher.
- Fusebox
- Box with switch & fuses. see also CU. See House Wiring for Beginners
- Gang
- Grommet
- rubber ring-shaped item that protects cables etc from the sharp edges of a hole. Also see blind grommet
- Halogen lamp
- a high temperature filament lamp. Popularly used as downlighters.
- Humidistat
- Device that switches electrical power according to humidity level. Usually switches power on when RH goes above its threshold value.
- LED
- Miniature solid state light emitter. Very low powered devices available in white and assorted monochromatic colours.
- Line
- Live wire
- M3.5
- the size & thread of screws used with standard UK electrical accessory faceplates.
- MCB
- Miniature Circuit Breaker, a pushbutton overcurrent cutout that replaces a fuse
- Mercury Lamp
- A high efficiency white discharge lamp with poor light quality. Sometimes used as white streetlights. Not as popular as they were 20-30 years ago.
- MES
- Miniature Edison Screw: screw-in bulb base widely used on torch bulbs.
- Metal Halide Lamp
- High efficacy white discharge light available in various versions of white.
- MICC
- Mineral insulated copper cable. A very high temperature rated rigid cable. Widely used for fire critical circuits. Known as pyro. Hygroscopic.
- Multimeter
- electrical meter that measures voltage, current (amps) and resistance. A worthwhile purchase for almost any DIYer.
- Neon screwdriver
- Simple voltage indicator. It is unsafe to rely on these when dealing with mains, as they give both false positive and false negative results.
- PAR38 & other numbers
- Spotlight bulbs.
- * PAR number gives bulb diameter in 1/8ths of an inch
- PAT
- Portable Appliance Test, electrical goods safety test.
- Pattress
- Backbox for electrical accessories (light switches, sockets, etc)
- PV
- Solar PhotoVoltaic, an electricity producing solar panel.
- R50
- 50mm diameter spotlight bulb.
- R63
- 63mm diameter spotlight bulb.
- R80
- 80mm diameter spotlight bulb.
- RCBO
- an MCB & RCD in one device. See Electricity Basics & Rewiring Tips
- RCD
- device that cuts the power if it detects earth leakage. See also Rewiring Tips. Compare ELCB.
- Relay
- Electrically controlled switch. The first electrical computers were made from thousands of relays.
- SBC
- Small Bayonet Cap. Miniature version of the more popular bayonet cap used on mains light bulbs.
- SES
- Small Edison Screw. The 2nd most common size of screw-in lightbulb base, smaller than ES.
- Socket
- electrical outlet into which a plug can be inserted.
- Sodium Lamp
- 2 different types of very high efficacy yellow and pink lighting. Much used for road lighting. Low pressure sodium lighting has the best energy efficiency of all lighting types.
- Solder
- Metal alloy used to join pipes and sometimes wiring. Lead & tin solder has long been used, but is no longer permitted for potable water piping.
- Striplight
- Linear lamp, either fluorescent or filament
- Switchbank
- Bank of 2 or more switches. Permits much greater control over lighting etc than just a single switch. Compare 'dimmer.'
- Switchboard
- Switchfuse
- Switch & fuse. Historic forerunner of the fusebox
- T4, T5, T8, T12
- Diameters of fluorescent tubes, in 1/8ths of an inch. Thus T12 is 1.5" diameter.
- T&E
- Twin & Earth, 3 core PVC cable used for most house wiring.
- Trip
- Any button or switch operated electrical cut-out, such as MCB, RCD, RCBO. A colloquial term.
- TT
- Earthing system using a local earth, usually a rod but may sometimes be a pipe or grid.
- Ufer
- A method of creating a very low resistance local earth connection, and eliminating potential differences between concrete floors and CPC during fault conditions, all at no significant cost.
- VA
- Volts multiplied by amps gives VA. This equals power for some loads, but is not equal to power for non-resistive loads.
- Whole House RCD
A deprecated way of installing an RCD such that a single low trip threshold device (typically 30mA) protects all the circuits in a property. While counter to the advice given in the present wiring regulations. installations of this type are still commonly found.
- VIR
- Indian rubber electrical wiring. Common half a century ago.