The importance of UPS for emergency lifts

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    To ensure compliance with safety regulations, a secondary source of power is required to feed all emergency lifts. For some installations, such as sports stadiums, a third level of backup power may be required. According to experts at Power Control, UPS systems can offer many advantages, yet they are often overlooked…

    Uninterruptible power supplies (UPS) are often overlooked as a backup supply of power for emergency lifts as they usually evoke images of large data centres and IT infrastructure. However, in order for a premises to comply with BS 9999 regulation, there must be a secondary source of power feeding all emergency lifts. In many cases, providing a secondary mains feed simply is not possible, so a UPS and/or generator combination is used instead.

    When an authorised person is present, emergency lifts provide an evacuation route for disabled persons in the event of a power outage. During normal operating conditions an emergency lift should be available as a passenger lift and not solely for evacuation or an occasional use of transporting goods. 

    With facility managers becoming increasingly more safety conscious, leading power protection specialist Power Control is keen to remind them of the ‘hidden’ considerations that cannot be missed. Commenting, the company’s special applications director, Matt de Frece, says: “Many people often overlook that in certain specific applications there may be a need for a third level of backup power. For example, often sports stadiums run on generator during games. 

    “If the site has a mains power cut while running on generator the majority of guests can remain and enjoy the event. However, at this time there is only one power supply to the emergency evacuation lifts, so if disabled guests are reliant on a lift to exit the building they would need to be asked to leave, which could be viewed as discriminatory. Installing a UPS in this application would prevent this scenario. 

    “In some circumstances, a UPS solution is preferable as it is easier to install into the lift plant room, often located at the top of the lift chassis. The logistics associated with installing a generator onto the top floor of a high-rise building can be costly and the space-saving benefits of a UPS system appeal to building managers.”

    Whether a generator, UPS system or both, these must operate the lift for either 60 minutes or three hours depending on the evacuation plan and whether immediate evacuation of the premises is possible. For example, hospitals and care homes require a longer evacuation process and so would need backup power for at least three hours.

    The emergency lift must be provided with communication networks from the plant room to the lift car and the main floor. It is recommended that the lift control panel is also fitted with a smaller single phase UPS solution to resume communication during a power outage. 

    The plant room typically requires a standalone three-phase UPS system compliant with the European compliance standard BS EN 50171 standard to provide backup power to the lift motor.

    De Frece explains: “A BS EN 50171-compliant UPS solution differs from a standard commercial backup power system as they would include enclosures that are resistant to heat and fire. 

    “In addition, the inverters also need to be capable of supporting 120% of the load requirements continuously, battery chargers need to be able to recharge the batteries to at least 80% capacity within 12 hours, the inverter shall be protected from reversal of battery polarity and the batteries should have a rated design life of 10 years at 20 degrees C. 

    “Power Control supplies a range of EN50171 UPS systems that have been designed based on standard, commercial UPS solutions, which means that spare parts and UK engineering support are readily available. All modifications to meet EN50171 standards are carried out at manufacturers’ factories to deliver quality confidence. 

    “Our long-standing UPS partner, Borri Spa, has its ECS [Emergency Central System] range of life safety UPS systems. Designed specifically to meet the EN50171 standard, these transformer-free, static solutions from Borri can be used as a CPSS [Central Power Supply System] instead of a distributed power supply, which delivers huge cost benefits as they require less sophisticated electrical design.”

    Available from 10kVA and 160kVA, the E8031/E8033 ECS (10-50KVA 3/1, 3/3) and the Ingenio ECS (60-160KVA 3/3) offer 10-year battery life, battery polarity reversal protection and charger temperature compensation. The Borri ECS range has also been designed with acid-proof battery cabinets and racks and IP20 metal enclosures as per EN605898-1.

     Power Control also offers a modular compliant solution from Legrand. The Legrand MCS CPS is available with 3-80kW modules and provides a highly intuitive scalable centralised UPS solution for life safety applications. 

    A fully adaptable single-phase, three-phase input/output system, the Legrand MCS achieves flexible redundancy and reduced MTTR (Mean Time to Repair) time.

    “These specialist UPS systems from Borri deliver efficient backup power solutions for a huge range of life safety applications from evacuation lifts and emergency lighting through to smoke extraction, warning systems and fire suppression,” says de Frece.

    “Power Control has seen the uptake of the Borri ECS and Legrand MCS range rise considerably over recent months as it is fast becoming recognised as an affordable and practical emergency power solution. 

    Finally, there are several additional points to consider when it comes to protecting emergency lifts, such as a variable speed drive (VSD). Due to the nature of motors, they have quite high inrush currents which often means the UPS needs to be oversized in order to cope with the starting current, which are often 8x or 9x the running current.

    “Fitted in between the UPS and lift motor, a VSD limits this inrush of electricity to 1x the running current, softening the initial start-up and not affecting the overall supply, and allowing a smaller UPS to be installed,” says de Frece. 

    “Also, there is a need to be aware of the potential risk of a regenerative load, a common occurrence with lifts when the UPS has no load from other equipment. 

    “The lift motor can become a generator and feed power in the wrong direction. Most lifts are sufficiently counterweighted to minimise this effect but care needs to be taken in the design if this could potentially be an issue.”

    When it comes to an effective power protection solution for emergency lifts, it depends largely on the size of the premises and the number of lifts requiring support. 

    A three phase UPS of 10kVA to 160kVA capacity is sufficient to replicate the mains supply normally serving the lift. Providing the ability to run the lift at normal speed and sufficient capacity to complete a required number of journeys, meeting BS 9999 regulations.

    1 COMMENT

    1. The regenerative effect in modern lifts is used to reduce the energy consumption so and emergency system should be off line and only activated when the utility feed is lost – and then it needs braking resistors to absorb the back-feed. I would have thought that it is much better, technically, reliably and commercially to just have a genset rather than a VSD/UPS/genset combination.

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