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Mains Power Supplies & Earthing Systems

The Electricity Safety, Quality and Continuity Regulations 2002 requires the electricity distributor to install the cut out and supply meter in a safe location, where they are mechanically protected and can be safely maintained.

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Incoming mains power supply

Mains Power Supply Location & Accessability

In accordance with this requirement the risk of flooding should also be taken into account. (see 'Preparing for Floods (ODPM, 2003)'. Distributors equipment and the installation consumer unit/fuse board should be above the flood level. Upstairs power and lighting circuits and downstairs lighting circuits should be installed above the flood level. Upstairs and downstairs circuits should have seperate overcurrent devices (fuses or circuit breakers).

Consumer units should not be installed where young children might interfere with them.

In accordance with these regulations and the contract for a grid/mains power supply, proposals for new installations or significant alterations to existing ones such as the installation of a solar PV system over 16A (3.6kW) must be agreed with the electricity distributor in advance of the work taking place.

Electricity Meter

Mains Power Supply System Requirements

The Electricity Safety, Quality and Continuity Regulations 2002 requires the electricity distributor (Regulation 27) to advise of:

  • The number of Phases
  • The Frequency; and
  • The Voltage

On request the electricity distributor (Regulation 28) should provide the following information:

  • The maximum prospective short circuit current at the supply terminals.
  • For low voltage connections, the maximum earth loop impedence of the earth fault path outside the installation.
  • The type and rating of the distributor's protective device or devices nearest to the supply terminals.
  • The type of earthing system applicable to the connection
TN-C-S mains power supply System

Protective Multiple Earthing (PME) (TN-C-S system)

Almost all new supplies to dwellings will be from PME distribution systems. With a TN-C-S system earthing for the installation is provided from the distributor's fused cut out where it is common with the PEN or Neutral conductor.

Except in city centres the conditions assumed for a TN-C-S system are:

  • The maximum external earth fault loop impedence Ze is 0.35 ohms.
  • The maximum prospective fault current is 16 kA

See: Earthing: Your Questions Answered (IEE, 2005) for further details and diagrams.

TN-S mains power supply System

Cable Sheath Earth (TN-S system)

The earth connection is the responsibility of the distributor and is made by connecting the earth connection to the sheath of the incoming supply cable. The connection should be secured with soldering or brazing.

A maximum fault level of 16 kA may be assumed and a maximum external earth loop impedence of 0.8 ohms.

See: Earthing: Your Questions Answered (IEE, 2005) for further details and diagrams.

TT mains power supply System

No Earth Provided (TT system)

TT installations may be found in rural locations with overhead supplies or where a distributor may be unwilling to provide an earthing terminal such as that for a swimming pool, farm or building site.

It is necessary to install an earth electrode with an impedence to true earth of the electrode not exceeding 200 ohms. This can be checked by carrying out an earth impedence test when the supply has been connected.

Metal gas, metal water or other metal service pipes are not to be used as the earth electrode. A seperate earth electrode must be installed with any present gas, water and other metal service pipes being bonded to the new Main Earthing Terminal.

See: Earthing: Your Questions Answered (IEE, 2005) for further details and diagrams.

Main Equipotential Bonding

Main Protective Bonding of Metal Services

In every installation, main protective bonding conductors are required to connect to the main earthing terminal for every extraneous-conductive part; including:

  • Water service pipes
  • Gas installation pipes
  • Other service pipes and ducting
  • Central heating and air conditioning systems
  • Exposed metallic structural parts of the building
  • Lightning protection systems.

When an installation serves more than one building, the above requirement must be applied to each building. In certain special locations and in installations of increased shock risk supplementary bonding is required.

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Solar PV Systems & Equipment, including Electrical & Roofing Systems

Grid-tie inverters, Hybrid Inverters, AC Coupled Inverters, Battery Storage Inverters, Off-Grid Inverters, Charge Controllers, Transfer Switches, Hot Water Controllers, Optimisers, Lithium Batteries, Lead Acid Batteries, Solar Panels, Mounting Systems, Test Equipment, Earthing Equipment, Electrical Distribution Equipment, Cable and Accessories

Wholesale Solar PV Equipment Suppliers

Deliveries to anywhere in the UK are quick, tracked and accurate, technical support (by phone and on site if needed) and design/product advice is available before, during and after installation. The recording and collating of serial numbers, factory and other test results, manuals any other information required for equipment warranties, add ons and extensions is included.

Trade, DIY and Retail Clients Welcome.

Bespoke system design, equipment testing and integration support as well as on-site technical support and job/equipment specific training is available for off-grid, hybrid, larger and or more complex systems.

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Mains/Grid Isolation and Surge Protection

Mains/AC Surge Protection Solar PV Systems

A whole house surge protector is installed to provide protection from transient overvoltages originating from the mains/grid. A whole house surge protector is installed directly inline and as close as possible to the incoming mains/grid supply meter, this allows for surge protection for all circuits and equipment including solar inverters, routers, stereos and other sensitive electrical equipment within the network. The addition of a 100Amp lockable isolator also allows for safe and convenient isolation of all electrical equipment within the network including consumer units, solar inverters, battery storage units and EV chargers from the mains/grid in one place.

Surge protectors are in compliance with the recently updated 18th edition amendment 2 of BS7671.

Mains/Grid Isolation and Surge Protection


Solar PV Surge Protection (DC Surge Protection)

DC Surge Protection Solar PV Systems

DC surge protection devices (SPDs) are installed between the solar panels and the solar inverter to protect both the solar inverter and the downstream electrical equipment from transient overvoltages of an atmospheric origin impacting the electrical system via the DC side of the system / the solar panels.

DC Surge protectors are in compliance with the recently updated 18th edition amendment 2 of BS7671.

Solar PV Surge Protection (DC Surge Protection)

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Articles: Further Information, Calculators & Solar Inverter Fault Codes

Lots of articles, calculators and technical information including links for further reading. Covering a range of topics related to the installation and maintenance of solar photovoltaic and electrical systems in the UK.

/Solar PV Information Articles

Engineering Recommendation G98

Grid Connections for Micro-Generators including Solar PV Systems and Elecricity Storage Systems in the UK. Under 16Amps Per Phase, grid synchronised.

Solar PV, Safety & The Building Regulations

Residential PV systems notifiable under Part P. Special consideration needed for Part A. A combination of serious risks for solar PV installers.

How to provide power to a house using a portable generator

In this article we show you how to power your home using a portable diesel, petrol or LPG generator. We look at changeover switches, the importance of earthing, generator loadings, how to isolate non essential loads. We ask where to locate the generator when it's in operation, how best to safely isolate the grid/mains power supply and switch to a generator supply.

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Areas Served:

We are located in Wanborough, very close to Swindon in Wiltshire, Southern England, UK. From here we service clients within a 90 minute driving radius including the towns, cities and regions below:

Swindon: Abingdon, Aldbourne, Amesbury, Andover, Banbury, Basingstoke, Bath, Berkshire, Bicester, Blunsdon, Box, Bracknell, Bradford on Avon, Bridgwater, Bristol, Buckingham, Burford, Burnham on Sea, Calne, Camberley, Cardiff, Carterton, Cheltenham, Chippenham, Chipping Norton, Chipping Sodbury, Cirencester, Corsham, Cricklade, Devizes, Didcot, Evesham, Eynsham, Faringdon, Frome, Fleet, Glastonbury, Gloucester, Gloucestershire, Hampshire, Henley-on-Thames, Highclere, Highworth, Hook, Hungerford, Keynsham, Kingsclere, Lambourn, Lechlade, Ledbury, Ludgershall, Lyneham, Maidenhead, Malmesbury, Marlborough, Marshfield, Melksham, Minety, Newbury, Newport, Oxford, Oxfordshire, Pewsey, Purton, Ramsbury, Reading, Ross on Wye, Royal Wootton Bassett, Salisbury, Shaftesbury, Shalbourne, Slough, Southampton, Stow, Stratford upon Avon, Stroud, Swindon, Tewkesbury, Thatcham, Tidworth, Trowbridge, Wanborough, Wantage, Warminster, Weston Super Mare, Wiltshire, Winchester, Windsor, Witney, Wokingham, Worcester, Wroughton and Yate.

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