There has been a proliferation of consumer units and associated products hitting the UK electrical market in the last couple of years.  Jake Green, Head of Technical Engagement with Scolmore Group, looks at some of the factors that contractors should be considering when sourcing distribution boards.

As a sector, we are only too familiar with the pressures of tight margins and the need to complete projects on time, to shorter programmes and within restricted budgets. Within these constraints, the appeal of a lower priced product, or more easily accessed product, may make sense in the short term, but can contractors afford to put themselves in a position where a product may fail to meet the requirements for which it has been specified, resulting in time lost, delays on site, or worst case scenario injury to a person? 

It is more important than ever that contractors have the security of knowing that the suppliers and brands they are working with are rigorously tested, fully compliant, will help deliver faster installation and are backed up with reliable customer support service.

When Scolmore entered the consumer unit market in 2021, it did so from its position as a leading organisation in the UK wiring accessories market with a long standing reputation for quality, reliability and innovation. The launch of Elucian brought to the professional contractor a comprehensive consumer unit and circuit protection range that was designed with the installer in mind. Compliant with all the latest regulations, the extensive collection of metal consumer units covers a broad range of installations and offers a number of features and benefits that enhance the products’ convenience, flexibility and safety properties.

Third party approvals

The consumer units in the Elucian by Click range are all tested, and third party approved to BS EN 61439-3 - Low-voltage switchgear and control gear assemblies - Distribution boards intended to be operated by ordinary persons (DBO).

DBOs have the following criteria:

• intended to be operated by ordinary persons (e.g. switching operations and replacing fuse-links), e.g. in domestic (household) applications.
• outgoing circuits contain protective devices, intended to be operated by ordinary persons, complying e.g. with BS EN 60898-1, BS EN 61008, BS EN 61009, BS EN 62423 and BS EN 60269-3. (All Elucian protective devices supplied by Click Scolmore are third party approved to the relevant product standard i.e. MCBs to BS EN 60898-1; RCBOs to BS EN 61009-1 and RCDs to BS EN 61008.)
• rated voltage to earth does not exceed 300 V a.c.
• rated current (Inc) of the outgoing circuits does not exceed 125 A and the rated current (InA) of the DBO does not exceed 250 A.
• intended for the distribution of electrical energy. 
• enclosed, stationary.
• for indoor or outdoor use.

Scolmore has a Declaration of Conformity to back up its third party testing. A Declaration of Conformity is a requirement for UKCA marking because it acts as signed proof that a product is safe to use. Scolmore’s Declaration of Conformity documentation is available on request.

AFFDS – the new kids on the block

Among the significant changes included in the Amendment 2 to BS 7671:2018 (18th edition of the IET Wiring Regulations) is a requirement for Arc Fault Detection Devices (AFDDs) in AC final circuits supplying socket-outlets in specific installations (detailed in Regulation 421.1.7). 

An Arc Fault Detection Device (AFDD) is a safety device which activates in the presence of series and parallel arc faults by monitoring the waveform (signature) of an arc. It does this by electronically analysing the waveform and operates when the waveform falls outside of predetermined values. The standard required for Arc Fault devices is BS EN 62606. This provides the minimum safety and performance requirements AFDDs shall conform to.

BS EN 62606: 2013+A1: 2017 General requirements for arc fault detection devices states that the purpose of an AFDD is, ‘…to mitigate the risk of fire in final circuits of a fixed installation due to the effect of arc fault currents that pose a risk of fire ignition under certain conditions if the arcing persists’.

As a relatively new product to the UK, demand for AFDDs has been high. As a reputable manufacturer, Scolmore has applied the same rigorous tests and procedures to ensure its AFDD products are safe, reliable and suitable for the intended applications.  

Causes of arc

Contact arcs can result from either direct or indirect contact between metal parts which are moving relative to one another or have little conductivity, such as a loose electrical connection or a break in conductor.

To generate an arc is a complicated process, but principally an arc fault is a function of the voltage and the distance between the two points of contact. Initially, an arc is composed of metallic vapours (for example, carbon) and current can flow through the damaged section. As the current flows through a material that is a relatively poor conductor, heat is built up due to the  heating effect.

Means of detection of arc faults

Manufacturers differ in how they choose to conform to the requirements of the Standard, however. Scolmore apply three characteristics in complex algorithms which, when taken together, will cause their AFDD to trip. These are:

• Noise – HF noise in the high kHz to the MHz region. This ‘noise’ is generated by the movement of the arc roots at the cathode. Whilst there are other sources of ‘noise’ which are naturally generated by electrical equipment operating normally, these are of a different nature and the algorithm filters them out.
• Continuous – ‘noise’ must not be of a brief duration or very intermittent. It is only a continuous process that will lead to the creation of a fire risk and, therefore, where ‘noise’ is intermittent this will not lead to the operation of the AFDD.
• Current variation – erratic variations in current and waveform distorting the typical sinusoidal waveform of the normal supply. A series arc will have an impact on the nature of the load current within a final circuit. At the point of arcing there will be an increase in heating with a corresponding variation in current. The AFDD algorithm will sense this changing current.

Unless all three elements are present the AFDD will not operate as it is unlikely a true series or parallel arc will be present.