2) The circuit protective conductors (CPCs) were terminated by twisting together and not by use of a proprietary means of connection; and 3) CPCs were exposed outside the enclosure and not sleeved.
This could have been avoided by ensuring that:
Good installation practice should have been followed and is outlined as follows: n In laying out the lighting plan for downlights, it should be ensured that the minimum clearance distance as required by the manufacturer is followed in relation to proximity to flammable materials associated with the building structure;
n Appropriate measures should be taken in locations where it is likely to be used for storage (for example, loft voids), to prevent the likelihood of flammable stored materials coming into contact with the hot surface of the downlights. This can be achieved by the use of a proprietary ‘downlight fire guard’;
n Terminations to downlights should be correctly made with cable sheaths entering the enclosure;
n CPCs should be sleeved inside of enclosures and be terminated by a proprietary means of connection; and
n Manufacturers’ instructions must always be followed.
Case study 2
The installation:
The electrical installation comprised lighting and power in an extension to a private members’ club, which was a licensed premises. The extension included a bar area, members’ lounge and toilets. The lighting comprised of ELV downlights installed in the ceiling voids, and some of these were accessible through a loft door giving access to the roofspace.
What went wrong:
The installing contractor had returned and completed some remedial work following a request from the club committee, who had complained about premature lamp failure of the downlights. Subsequently, the committee was still not satisfied with the outcome after the contractor had completed the remedial work, and it was decided to employ an independent electrical contractor to carry out a periodic inspection report. This report identified problems associated with the
installation of the downlights. Our inspection was commissioned by the club committee to obtain an authorative opinion as to the compliance of the installation to the appropriate standards – and, in particular, the installation of the downlights. Our inspection identified evidence of heat degradation
to connector blocks terminating the fixed wiring cables to the downlights and heat degradation to the PVC- insulated and sheathed cables installed in close proximity to the downlights.
The outcome:
While the most onerous outcome of this issue was said to be premature lamp failure, in our opinion the likely outcome could have been the initiation of a fire.
What should have been done?
We concluded that the heat degradation/damage to the fixed wiring cables in close proximity to the downlights and the terminal blocks was due to excessive temperature rise in the vicinity of these, due to the high surface temperature inherent with this type of downlight – as well as the inability to adequately dissipate the heat due to the covering of the downlight with thermal insulation.
This could have been avoided by ensuring that:
n Thermal insulation did not come into direct contact with the downlight and that there was adequate free-space clearance around the fitting by use of a proprietary ‘downlight fire guard’;
n Terminations to the downlight, which were not incorporated in the fitting, were terminated in a proprietary enclosure;
n Cables installed in close proximity to the hot surface of the fitting were heat-resistant to the appropriate temperature, and that this type of cable was used as the final connection to the fitting.
n Manufacturers’ instructions were followed.
Summer 2010 ECA Today 47
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, fires and disputes regarding compliance with British Standards, the diversity of which includes lighting and power, emergency lighting and fire detection and alarm systems. See
www.elecsa.co.uk or email:
enquiries@elecsa.co.uk
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