All change in 17th Edition for wiring of smoke alarms

Important changes to national wiring regulations are set to clarify the way smoke and heat alarm systems should be designed for both new and existing housing. They also open the door for cost-effective protection against carbon monoxide, as Gerald Jones, Kidde Fyrnetics Business Manager of Kidde Safety Europe, explains.

The 17th Edition of the IEE Wiring Regulations (BS 7671:2008) takes effect in July. In a major change, it now requires circuits of safety services - such as hard-wired smoke and heat alarms - to be independent of other circuits and unaffected by, for example, “tripping-out” of other circuits. Now, smoke and heat alarms can no longer be powered from lighting circuits, despite being a common practice endorsed in both national Building Regulations and BS 5839-6:2004, the current Code of Practice for domestic fire alarm systems.

However, the new requirement for an independent circuit is easily and inexpensively achieved using “three core and earth” cable, where the third cable simply provides the interconnect signal, and this is set to become the normal method for hard-wired alarms in future.
The justification for wireless interconnection are called into question therefore, in view of this change, as simply powering alarms off local lighting circuits are no longer compliant.

EXISTING AS WELL AS NEW HOMES

Hard-wired alarms with backup power are a Building Regulations requirement for new-build but steps are also being taken to require them in existing homes, for example with the Housing (Scotland) Act 2006 and Housing Health and Safety Rating System which applies to England and Wales, in line with BS 5839-6:2004. This is particularly important for rented properties where landlords have a duty of care to their tenants and where battery failure or removal results in non-functioning alarms – sometimes with fatal consequences. So, hard-wired smoke and heat alarms will become a more common feature of refurbishment and rewiring programmes and, of course, the 17^th Edition requirements will now apply.

Here again, the “three core and earth” system offers the most economic solution to power and interconnect them.

In addition to fire, incidents of carbon monoxide poisoning continue to feature regularly in the news. Despite specific legislation requiring them – at least at the moment - we are seeing a growing demand for CO alarms in both new and existing homes. Here again, landlords have a legal duty to protect their tenants and the same failure problems can be encountered with stand-alone battery alarms. As hard-wired CO alarms are also ‘Safety Services’ in the 17^th Edition, the simple “three core and earth” approach can simply be extended to

CO alarms as well, on the same circuit as smoke and heat alarms.

To make the most of interconnection, some alarms have special facilities - such as Kidde Fyrnetics’ unique ‘Smart Interconnect’ – to provide expanded whole-house protection for little additional cost. For example, with Smart Interconnect, when a smoke or heat alarm is triggered by a fire, all the interconnected alarms - including CO alarms - activate to alert occupants of danger.

When a CO alarm is triggered by carbon monoxide, all the interconnected CO alarms activate. It is important to have different, distinct alarm sounder patterns for carbon monoxide and fire – preferably supported by different digital display messages - as totally different actions are required with a CO event compared with fire.
Those systems requiring operation of an isolation switch then location of the activated alarm before deciding what action to take are worryingly unrealistic.

WHOLE HOUSE PROTECTION

With systems such as Smart Interconnect, a CO alarm in the bedroom can act as the sounder for smoke/heat alarms elsewhere. For a minimal extra cost, this arrangement overcomes the inadequacies of corridor and landing only smoke alarms in waking sleeping occupants, by ensuring that the sound level required by BS 5839-6:2004 is generated at the bed-head - as well as protecting sleeping occupants against carbon monoxide poisoning. But, with just a few more units, comprehensive whole house protection can be achieved with alarms positioned wherever there may be a risk or they are needed to alert occupants.
These kinds of innovations make the most of the independent circuit requirement demanded by the 17^th Edition

and will become standard practice to meet modern safety demands in future.

A guide covering national Building Regulations, the Code of Practice and other requirements for both fire and carbon monoxide safety in housing is available free of charge from Kidde Fyrnetics via www.smoke-alarms.co.uk using the ‘Contact us’ link

6/2008