Glossary

This glossary has been written to help explain some of the words and phrases uses in electrical jargon, and wherever possible, we have included the relevant BS7671:18 Amendment 2 numbers which you can use for further reading. This glossary will be periodically updated and amended.

BS7671:2018 (Amend 2) Regulation/Section or Chapter Number

Abbreviation

Phrase/Wording

Explanation

Alternating Current

This is used to power homes across the UK

421.1.7

AFDD

Arc fault detection device

Detects arcing in an electrical circuit. These are mandatory in hotels and buildings with multiple occupancies

BSI

British standard

The British standard institute is the UK's National Standards Body

BS7671

Electrical regulations

The British Standard for electrical wiring regulations. Currently, it is the 18th edition (amendment 2) which superseded the previous version in September 2022

C&G

City & Guilds

A Royal Chartered Institute that sets, provides, and monitors training standards

Consumer Unit

This is where all circuits in your property/business are isolated from (see guides for more information)

Chapter 82

Direct Current

This is used primarily in solar PV installations

DNO

Distribution network operator

This is your authorised electricity distributor

Chapter 64

EICR

Electrical Installation Condition Report

A periodic electrical test is carried out to determine the state of the wiring system. This test is recommended before buying a property, during any major alterations and at set period times (see guides for more information)

Chapter 82

EPS

Emergency Power Supply

This is normally a dedicated socket that can be used in the event of a power outage. The socket is powered by a battery storage system and has usage limitations

Section 722

Electric vehicle

See OZEV

Fault Current

This is where there is a connection between parts of a circuit where there should not be. This is normally due to a fault in the wiring or the equipment being used

First Fix

This is the initial phase of installing all wires and boxes in a property, ready for the second fix stage

Kilowatt

A measurement of power. There are 1000 Watts in 1kW

kWh

Kilowatt-hour

A measurement of energy used over time, which is measured in kW

kWp

Kilowatt peak

This is the maximum power that your solar array can produce. The atmospheric conditions must all be optimal for this to occur. Solar systems are often over-sized to allow for this.

Part 2/Chapter 41

MCB

Miniature circuit breaker

This device protects against overcurrent and is situated in your consumer unit

MCS

Microgeneration Certification Scheme

This is the renewable energy standards organisation. You can only become a member of the MCS scheme if you are a qualified electrician, have completed a relevant renewable training qualification and are a member of an electrical trade body i.e. Napit. An inspection of all paperwork and at least one completed installation is carried out annually to prove competency

MPAN

Meter Point Administration Number

This number is unique to you and will be displayed on your electricity bill

National Grid

Is responsible for the supply and transmission of the UK’s electricity

NAPIT

National Association of Professional Inspectors and Testers

You must be a qualified electrician to become a member. An inspection of all paperwork and at least one completed installation is carried out annually to prove competency

Overload Current

This is where too many items are being used on a electrical circuit. When this happens, the overload device in your consumer unit will operate

OZEV

Office for Zero Emission Vehicles

This is the government office for electric vehicles. This is run by the Department for Transport

RCBO

Residual current breaker with over-current protection

This device protects against overcurrent and fault current and is situated in your consumer unit. These devices are now the preferred method used in consumer units

531.3.3

RCD

Residual current device

This device protects against earth fault currents and is situated in your consumer unit. There are various types of RCD, each with is own application.

Second Fix

This is where all sockets, switches etc are fitted, normally after plastering has taken place within a property

443.4.1

SPD

Surge Protection Devices

These are now fitted to protect your electrical installation against transient over voltages. All new works will require a SPD to be fitted

Self Sufficiency Percentage

This is a calculated percentage given at the design stage of a solar/battery storage installation. The higher the percentage the more energy efficient you are. For example, if you are given a self-sufficiency of 75%, this value is the amount of useable electricity that your solar/battery system will provide meaning that you will only purchase 25% of electricity from the national grid

SEG

Smart Export Guarantee

This is a set tariff paid for any exported solar generation. Different companies will have different tariffs. A popular tariff with both solar and EV vehicle users is from Octopus energy

Solar Array

This is the collective term for all of your solar panels. This can be further separated into strings

WATTS

A measurement of electrical power