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■ Reference to the manufacturer’s data sheets and specifi cations; or

■ Measuring the circuit current by use of a test instrument such as a clip-on ammeter.

An adequately-rated controller could then have been

selected based upon this data. The lesson to be learned from this incident is to not take anything for granted. Just because an item or piece of electrical equipment is fi tted does not necessarily mean that it is fi t for purpose. Clearly, in this case the original design specifi cation was fl awed, as apparently all apartments had had the same controllers fi tted. The manufacturer’s instructions for this type of controller state ‘only suitable for central heating control’.

What do the regulations BS7671:2008 require regarding this issue? The requirements of Part 1 and Part 5 include requirements for: ■ Electrical equipment not to present a fi re hazard to surrounding equipment;

■ Electrical equipment to be suitable for the design current of the circuit;

■ Functional switching devices to be suitable for the most onerous duty that they are expected to perform; and

■ Installation in accordance with the instructions provided by the manufacturer.

Case 2

The installation: The electrical work consisted of a rewire of a small domestic property. This was completed to the 16th Edition IEE wiring regulations (1991). A split load consumer unit had been installed with a bank of ‘unprotected’ ways connected directly from the main switch supplying lighting and other fi xed wiring circuits, and a bank of 30mA RCD protected ways supplying socket outlet circuits. The wiring system was PVC insulated and sheathed cables.

Reason for the inspection: After the re-wire had been completed, another tradesman working at the property told the owners that some aspects of the rewiring work were not to the required standards. This prompted the owners to engage a second electrical contractor to carry out an inspection report. On receipt of the report, we were engaged to investigate the issue. While there were several issues raised in the report, the major one was the connection of the earth terminals in the consumer unit to the neutral terminals by means of a cable link, to provide a return path for fault current in the absence of a means of earthing having been provided by the distributor.

The outcome: As is probably the case with most hazards and unsafe practices such as this, they have the potential to harm and cause injury but often, because of the circumstances,

Autumn 2010 ECA Today 61

this does not happen. In this instance, the potential hazard was nothing more than that and, as such, did not manifest itself into an accident causing injury. However, the potential was present for injury by electric shock – if, for any reason, the neutral had become disconnected on the supply side of the shorting connection from neutral to earth in the consumer unit. In such an instance, all exposed and extraneous metallic parts within the house could have become charged with phase voltage.

What should have been done? The consumer unit earthing terminals should have been connected to suitable and adequate means of earthing, in compliance with the regulations at the time of installation.

This could have been avoided by ensuring that: ■ A survey of the electrical supply was undertaken prior to commencement of work to ascertain the type of earthing system in place, and its suitability. An external earth fault loop impedance test (Ze) would need to be carried out as an element of ascertaining the suitability of the earthing system;

■ A consumers’ earth electrode is installed if there is no means of earthing or the means of earthing is inadequate; or

■ The distributor reinstates the integrity of the existing means of earthing, if this is inadequate.

Note: The distributor of electricity has no obligation

under the Electrical Supply Quality and Continuity Regulations (ESQCR) 2002 to supply an earthing facility other than for new and upgraded PME supplies. To conclude, it is understood that the installing

contractor was advised to make the connection between neutral and earth. It is a sobering thought that advice is not always good advice.

More info

ELECSA offers an inspection service providing expert witness reports for clients including local authorities, trading standards, solicitors, electrical contractors and private clients. It is listed in the UK Register of Expert Witnesses and accepts commissions from clients related to incidents of electrocution, fi res and disputes regarding compliance with British Standards, the diversity of which includes lighting and power, emergency lighting and fi re detection and alarm systems. See or email:

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