A Complete Guide to Evacuation Lift Safety and Central Power Supplies
Lifts without UPS risk avoidable downs
The growing number of mid and high-rise buildings in the UK has led to many facilities/building managers reviewing traditional solutions for vertical evacuation. In both commercial and residential buildings, it is imperative that people can evacuate quickly and safely regardless of their physical capabilities.
Updates to UK legislation BS 9999 Annex G and past events where a lack of suitable lifts has contributed to devastating outcomes have resulted in a significant increase in enquiries for specialist backup power supplies for lifts.
It is often up to the facilities manager to oversee that a building’s passenger lifts, evacuation lifts, firefighting lifts and refuge areas comply with safety standards so it is imperative that the different types of lifts are understood and so are the regulations surrounding them.
For a standard passenger lift to be used in an emergency either as a firefighter lift or emergency evacuation lift, it must comply with BS 9999 Annex G (fire regulations) which means there must be a separate EN 50171 rated backup power supply to the lift, independent of the mains supply. Otherwise, the passenger lift would have to be ‘grounded’.
Evacuation Lifts
Specifically designed to be used in an emergency situation, evacuation lifts are particularly beneficial for people who are unable to evacuate a building using stairs. These lifts are generally used as normal passenger lifts until required to evacuate people.
As well as needing a separate backup power supply, other features include a cause and effect interface between the lift control system and fire detection equipment, an emergency intercom, a management plan to determine operational procedures, a trap door within the lift car and a lift car that meets the minimum size requirement.
Firefighting Lifts
A firefighting lift is for the fire and rescue service to facilitate the safe conveyance of firefighting equipment and personnel in the event of an emergency.
Like evacuation lifts, firefighting lifts must meet BS 9999 regulation and therefore also require a separate backup power supply. It must provide the same functionality as an evacuation lift with the main difference of added water protection of the electrical components in the lift car and the lift must reach the furthest floor from FSAL in 60 seconds.
Consideration: Regenerative Loads
Despite many improvements toward safety and ease of use, lifts are still based on the same counterbalanced technology that was invented in the early 1900s. Counterbalancing the weight of the load in the lift reduces the amount of force needed to move the car up and down which means less energy is required. Whilst this operation method is efficient, it can result in regenerative energy.
The lift draws power in one direction and in the other direction it gives the power back. When operating on a mains supply, this means the power is returned to the grid. However, when drawing power from a UPS or CPSS, the return of power could cause a rise in voltage above the DC bus’s safe design levels and cause damage to the DC capacitors, rectifiers and inverters.
Power Control have experience in designing solutions that ensure the CPSS is protected against regenerative power, safeguarding the critical infrastructure.
Regulatory Requirements
Building Regulations form the regulatory foundation of a new building that is being built or an existing building that is undergoing significant refurbishment. It includes health and safety requirements for all aspects of the building.
Next is the Regulatory Reform (Fire Safety) Order 2005, which stipulates that a responsible person for the building must be elected to comply with fire safety management requirements under this legislation. This is typically a building manager or building owner.
As per BS 9999, it is up to the responsible person to assist in the evacuation of disabled persons in the evacuation lift as they are not permitted to evacuate themselves.
While BS 9999 regulates fire safety in the design, management and use of non-residential constructions, BS 9991 does the same for residential buildings. Which one to follow depends on the building’s function.
BS 9999/ BS 9991 Independent Power Supply – UPS vs Generator
A second power source, independent of the primary site-wide power source must be present for both types of emergency lifts.
Up until recently, the secondary power supply would typically be a diesel generator as it was believed that they were the only type of power supply that could meet the runtimes required by BS 9999, BS 9991 and BS 7671. However, with buildings getting taller and emissions in city centres becoming more of an obstacle, many building managers, consultants and specifiers are looking for alternative types of backup power.
A modified type of uninterruptible power supply (UPS) called a central power supply system (CPSS) is specifically designed to meet EN 50171 standards that satisfy the safety needs of BS 9999, BS 9991 and BS 7671.
The CPSS systems have sufficient run time to meet the needs of the evacuees for either 60 minutes or three hours depending on the evacuation plan and whether immediate evacuation of the premise is possible. Some premises such as hospitals and care homes require the full three-hour evacuation time whereas smaller facilities require less.
CPSS systems are smaller and lighter and more environmentally friendly than diesel generators. with higher efficiencies and more flexible installation options, they are far less of a logistical headache for building managers and solution providers.
Secondary power supplies cannot and should not be risk assessed out!
Contrary to what some building managers believe, secondary power supplies are mandatory and cannot simply be risk assessed out.
Since the release of BS 9999: 2017, there has been confusion over clause 45.9 which refers to risk assessments to evaluate whether the lift meets the recommendations given in Annex G and suggests that a lift not specifically designed for evacuation purposes (i.e. firefighters lift) can be used provided that it gives the same functionality as an evacuation lift and there is a suitable risk assessment carried out.
However, Clause 37.2.3.3-h (note 5) details that if the power supply arrangement is being used for applications additional to an evacuation lift i.e. firefighters lift or other safety reasons then a secondary power supply is required and therefore cannot be risk assessed out.
NOTE 5 “For evacuation lifts, it is often acceptable to provide a supply from a single intake to the premises, provided that in all other respects the configuration of the circuits within the building and other fire protection measures detailed above and in BS 8519 are as recommended. A secondary power supply from a separate substation or standby generator is not required unless that supply arrangement is necessary for other fire safety reasons (e.g. to supply a firefighters lift or smoke control system)” 1
How to ensure compliance?
The easiest way for a building manager to ensure compliance with all safety regulations as well as have peace of mind that all building users will be safe in the event of an emergency is to contact a supplier of backup power supplies. As a specialist in the field, they will be able to specify the most suitable and compliant central power supply for the needs of the premises.
Do I need a UPS on a passenger lift?
With a passenger lift being grounded during an emergency situation there are no specific regulations relating to secondary power supplies. However, Power failures and anomalies aren’t just a result of an emergency.
With the nation’s energy outlook appearing bleak and the head of the National Grid warning of energy being switched off in January and February 2023, smaller uninterruptible power supply (UPS) can be considered for passenger lifts.
One option is to install the UPS into the control panel of the lift so during a power outage the UPS will operate the breaks and ensure the safe return of the lift cart. This prevents passengers from being stuck in between floors until the mains power supply resumes.
The UPS can also be installed to provide backup power to the lift intercom system. If there are any issues with the lift when the mains power is out, passengers can still access help.
Conclusion
Building safety regulations are in place to keep users of the building safe during an emergency.
An evacuation lift with all the required safety features including a backup power supply could be the difference between people who are unable to evacuate a building using stairs getting out safely or being stuck in a dangerous building.
Central power supply systems (CPPS) compliant with EN 50171 are by far the easiest and cheapest option for complying with the need for an independent power supply system on emergency lifts and cannot be ‘risk assessed out’.