David Garrett, Head of Product Management for Wylex, has some interesting views on Amendment 3 to the Wiring Regulations.
Since the launch of ‘Amendment 3 Consumer Units’, installers and speciﬁers have increasingly turned their attention to the consideration of ﬁre safety issues relating to their new installations. Rising numbers have, as a result, expressed an interest in learning more about the inclusion of intumescents into consumer units, with a view not only to improve ﬁre safety in new metal compliant enclosures, but also to provide a quick and cost-effective improvement to existing installations where for example local authorities have a large installed base and an extended replacement programme.
The new Regulation (421.1.201) in Amendment 3 requires consumer units and similar switchgear to have their enclosures made from non-combustible materials (e.g. steel) the purpose of this is to contain (as far as reasonably practicable) any ﬁre within the non-combustible enclosure and to minimise ﬂames from escaping. Electrium have been working in close liaison with one of the UK’s premier manufacturers of intumescents (Tenmat) and BM Trada, one of the UK’s foremost ﬁre test authorities, having carried out extensive tests to fully assess the beneﬁts of such practice.
Metal consumer units will contain ﬁre better than plastic consumer units, but many users have expressed concerns, particularly over cable entries, where these unavoidably penetrate the non-combustible barrier of the steel enclosure. Depending on how many knockouts are removed, how well the cables enter the equipment, there may be a reduction in the capability of the enclosure to contain a ﬁre that occurs. This is because ﬁre paths may form along the cables and through the cable entries to other combustible materials in the surrounding external area. The IET and other industry organisations have partly addressed these concerns with advice for installers to ensure that the requirements of BS7671 & BSEN61439-3 are met i.e. that the installed unit achieves IP4X on the top elevation and IP2XC elsewhere.
“Metal consumer units will contain ﬁre better than plastic consumer units, but many users have expressed concerns, particularly over cable entries, where these unavoidably penetrate the non-combustible barrier of the steel enclosure.”
However, customer anxieties remain regarding a large number of cable entries possibly undermining the ﬁre safety intention of this new and important requirement.
Responding to the research and thus addressing these concerns, Wylex has introduced a range of self-adhesive intumescent material strips which, when exposed to heat, rapidly react to ﬁll the consumer unit. The resultant “char” ﬂows around the cables and devices and effectively smothers the ﬁre and reduces the oxygen supply, subduing or extinguishing the ﬁre at source.
Once expanded, this highly insulating char also restricts the heat of any ﬁre from reaching the steel enclosure and thus minimising the external temperature of the unit. This is an important added consideration; if the unit were unprotected by intumescents, and should a ﬁre remain unchecked and undetected within a steel enclosure, it is possible for the external surface to reach temperatures that could ignite surrounding materials in contact with the steel surface. Consumer Units protected with this Wylex innovation do not reach such temperatures.
The potential ﬁre risk with insulated consumer units has been clearly demonstrated by the ﬁndings of London Fire Brigade, however the use of plastic consumer units is still permitted in commercial (non domestic household) applications. As with the steel enclosures, the ﬁtting of this strip dramatically reduces the potential for a ﬁre to propagate. In fact under test, a plastic unit with the intumescent strip ﬁtted ran for 90 minutes with no sign of any external damage or elevated temperatures and the intumescent char was seen to fully smother and insulate the heat source from the rest of the unit minimising the chance of ﬁre propagation. However, an unprotected plastic consumer unit saw ﬂames propagate after a few minutes.
Clearly the use of this product enhancement aids compliance with, and exceeds the intentions of, regulation 421.1.201 which is clearly a desirable result. In all tests, the use of the intumescent strip reduced the risk of the ﬁre spreading from the consumer unit, and as a result of this work, it is highly recommended that it should be ﬁtted in all new installations and considered for retroﬁtting to existing units until such time as a fully compliant replacement is installed.