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How changes to BS 9251:2021 could save lives

Kate Aldridge

Kate Aldridge

Group Brand Manager at Power Control
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Kate Aldridge, Group Brand Manager at Power Control, explains how recent changes to BS 9251:2021, which make secondary power supplies mandatory, could quite literally save lives. 

The new BS 9251:2021 came into effect on June 30, 2021, and contains some quite significant changes that could see many landlords and residential building owners being caught out. The standard gives recommendations for sprinkler systems installed for life safety purposes with additional benefits for property protection.

The biggest update is the introduction of a new category of sprinkler system, category 4, which applies to residential and domestic buildings over 18 metres in height or above four storeys (whichever is shorter).

Sprinkler systems in this category should be ‘provided with a back-up power supply and automatic changeover functionality’. This means two power supplies should feed the sprinkler system. A mains supply as the primary power source, and an uninterruptible power supply (UPS) as a secondary power source, with an automatic transfer switch to transfer the load from mains to UPS in the event of a mains power failure while the sprinkler is in use.

Since the Grenfell tragedy in 2012, a lot of money has been spent on making high-rise buildings safer for their residents and those in the building. This has largely been achieved through regulatory updates surrounding life safety equipment.

Backup power supplies such as UPS systems are required on other life safety systems with recommended autonomies and runtimes, so it was only a matter of time before BS 9251 was also updated to include stricter safety recommendations for sprinkler systems.

A reliable power supply is critical during an emergency as most life safety systems are reliant upon electricity to operate. A drop or fluctuation in power could result in the failure of these critical systems resulting in a risk to life.

The recent Storm Arwen showed just how vulnerable the mains power infrastructure is. As winds of over 98mph tore down power lines on November 26, over 3,000 residential buildings in the North East of England lost their power supply for over a week. By December 6, there were still 86 residential properties without power in Cumbria and 30 in Scotland.

Had there been an emergency such as a fire during this prolonged outage, those without a secondary power supply would have been without power to their life safety systems. Sprinklers would have been out of action putting the lives of residents at risk.

As Storm Barra hit the UK and Ireland on December 7, many more have been left without power with a danger to life in some parts due to the conditions. For owners of residential buildings, it is crucial to ensure residents are kept safe if a fire were to occur by keeping up to date and adhering to safety regulations such as BS 9251.

Residential property owners must also note that should a battery backup be used as the secondary power supply to support life safety systems; it should be compliant with BS EN 50171 regulation.

This standard sets out a requirement for a minimum of 120% permanent overload capacity, central power supply systems (CPSS) are specifically designed to meet this requirement as they have larger batteries, which gives them a much higher overload capacity.

Also set out in the EN50171 is the requirement for the batteries to have a 10-year design life and the charging current must have a 10-hour capacity (must be at least a C10 rated battery) with polarity reversal protection where reversed battery connections can be done without damage or impact.

Contractors, engineers, surveyors and architects are among a larger list of people who need to be aware of the amendments to the 2014 edition of BS 9251.

Although the amendment to BS9251:2021 only applies to new constructions, it is recommended that existing buildings update their sprinkler systems to ensure the safety of residents. It is important to consult with backup power specialists when retrospectively fitting a secondary power supply to ensure the correct one is specified to suit the exact needs of the infrastructure.

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