SPECIAL FEATURE
UPS & power management
Cabling and electrical installation
Once the equipment has been located on site , attention can turn to cable entry and termination . Most medium to large UPSs require bottom cable entry ; this must be accommodated whether the system is to be installed in a plant room , which typically has a solid floor , or a computer room , where raised floors are more likely .
For a solid floor , a trench can be cut to lay the input and output AC cables
Mike Elms is technical manager for Uninterruptible Power Supplies Ltd . With more than 20 years of experience in the UK power protection business in both sales and engineering roles , Mike has an extensive knowledge of designing and specifying UPS systems for data centres across the IT , financial and telecom market sectors . and battery DC cables , and run them beneath the cabinet for connection to the UPS terminals . Alternatively , the UPS cabinet can be mounted on a steel plinth of sufficient height to allow satisfactory cable bend radii through 90 °. This is particularly important for sizeable UPSs with large cross sectional area cables .
Computer rooms often have raised flooring , permitting containment and access for computer equipment network and power cabling , and sometimes to facilitate underfloor cooling . These provide convenient routes for the UPS power and battery cables , which can be brought into the UPS cabinets via bottom access . The UPS ’ s weight , especially if it contains batteries , may be enough to require a steel plinth to distribute the load . The plinth stands on the subfloor and is adjusted until its upper surface is flush with the raised floor surface .
Performing the electrical installation is a task for experienced and qualified electrical contractors , employed either from recommendation or by the UPS supplier . In either case , references and evidence of previous successful installations should be sought and obtained . All installation work must be carried out in strict accordance with the manufacturer ’ s instructions and strict compliance with prevailing local electrical installation legislation .
The electricity supply required by high power UPS equipment will have a significant impact on the existing cabling and switchgear , so careful integration with these will be necessary . However , detailed planning at this stage will be rewarded by time and cost savings in the future if it ensures adequate provision for any potential business growth and extra UPS capacity . An integrated , purpose designed panel incorporating input and output switchgear for each UPS cabinet , together with a system isolator and wraparound bypass switch can reduce the system design burden , simplify cabling and shorten cable runs . It also minimises design and implementation complexity , saving time and costs .
When designing the power feeds from the UPS units to the distributed components of the critical load , it is important to choose electrical circuit routes and circuit breaker sizing that provide satisfactory discrimination downstream of the UPS system . This is to ensure that a single load fault only trips its local protection device , without unnecessarily shutting down wider sections of the power system and needlessly losing productivity .
An external maintenance bypass switch should also be provided , allowing the entire UPS system to be physically and electrically isolated for a swap-out or move without interrupting power to the load . Also , to ensure personnel safety and equipment protection , correct earthing is essential . All earthing points within the UPS circuits must be connected to a properly planned and secure earthing system .
Commissioning and load bank testing
These steps to UPS installation should be complemented by equal care with commissioning . The small additional investment necessary to use the UPS supplier ’ s trained and experienced technicians is more than offset by a number of benefits . These include a thorough check of the entire system installation , acceptance of environmental conditions and complete warranty cover on all UPS equipment . All equipment serial numbers will be registered with the supplier , and the UPS user will be trained in the operation of their system .
Load bank testing should be used to validate operational performance and prove battery autonomy under full load . It is recommended to perform the load bank test one week after commissioning as voltages across the battery blocks have equalised and the battery is fully charged .
Conclusions
The steps above are logical , and , provided qualified technicians are available , simple to perform . However , in Uninterruptible Power Supplies Ltd .’ s long experience of helping customers specify and install UPS systems , they provide a vital complement to the UPS ’ s technological features in establishing a successful and durable power protection solution .
Accordingly , from a project ’ s outset , discussions between UPS users and potential suppliers should encompass not only the equipment ’ s technical specifications and maintenance support contracts , but also the practical aspects of how the UPS system is to be set up on the user ’ s premises , and how the supplier can advise and help with this process .
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