Electrical Glossary

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.

Cable ties

Self locking plastic strap to secure cables

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.

Flex

flexible electrical cable. The flexibility results from using stranded conductors.

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.

Intumescent Hood

Junction box

Box containing connection points for cables. Fire resistant.

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.

Ring circuit

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.

Singles

Cable with a single conductor. Used inside conduit & trunking

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.

See Also

Glossary

Category:Electrical

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