Smaller-scale UPS systems

UPS systems are typically viewed as either large-scale installations for data centres, or small units residing under a user’s desk to support a single PC. While both these views are valid, there is also another class of users – organisations that have a critical need for a secure, continuously available IT resource, but cannot justify a dedicated data centre.

Such organisations often choose to run an IT facility comprising a smaller-scale computer network within their own office premises instead. In this article, Tan Yu Ming, General Manager at KOHLER Uninterruptible Power, looks at the UPS needs created by these circumstances, and the solutions available to meet them.

Large-scale computer failures have the capacity to make national headlines not just because of the number of people they affect, but also the consequences it has for those affected. Imagine, for example, that your bank’s IT infrastructure fails, and you can’t draw any cash out of an ATM, or you’re stranded in a remote garage and unable to pay for the fuel you’ve just taken.

Now imagine another scenario: It’s six in the evening, and you’re due to make a critical presentation tomorrow. You go to your desktop PC to download your Powerpoint presentation to your laptop – you meant to do it days ago, but somehow never got round to it – but there’s no power to your desktop. Lack of power also stops you from retrieving the backup copy from your Cloud storage.

Pressures on small and medium office IT systems

A problem like this typically arises within a small or medium office system environment rather than a large-scale data centre. The consequences affect far fewer people, but as we can see, could be just as critical for those that are involved. Continuous IT availability remains essential irrespective of the size of their organisation or IT resource.

Ensuring this availability, just as for a data centre, depends heavily on providing clean, uninterrupted power from a well-designed UPS system that is correctly matched to its working environment. Below, we look at the points to consider when choosing a UPS system scaled to an office environment rather than a larger, dedicated data centre.

The underlying pressures on an office IT manager will be the same as those on a data centre manager, albeit scaled down; he will require continuous power with protection from power surges, sags and spikes as well as complete power outages, delivered from a UPS system that is cost-effective to purchase, right-sized for his environment and energy-efficient to run. Scalability will also probably be important in case the organisation grows over time.

Office-scale UPS systems: A choice of capacity

These smaller-scale requirements are well recognised by UPS suppliers, many of which offer a range of solutions from below 1kVA up to 50kVA. The smallest systems comprise single-phase units for supporting a single desktop PC, which can be plugged into a normal 13A mains outlet. Typically implemented within a PC tower or mini-tower form factor, such units are aesthetically and technically suitable for installation next to the PC they are protecting. They are available with on-line, off-line or line-interactive topologies, although on-line is recommended as the only way of ensuring that fully-protected power is supplied at all times.

KOHLER PW 1000/OT UPS System

KOHLER PW 1000/OT UPS System

Similar but slightly larger systems, rated to a few kVA are also available. They may still be portable and operate from a single-phase IEC plug, however their increased rating allows them to power a fileserver or complete workstation. They may also support an extended battery cabinet to offer increased battery autonomy. Remote alarm systems are unlikely to be necessary for either these or the previously-mentioned systems as they are designed to be installed next to the protected load and its operator. However if the load is critical, SNMP communications or automatic shutdown software may be required.

Larger systems from 3kVA to 20kVA are available to support networks rather than single PCs or workstations; typical examples include complete office networks, small server farms or communications centres. Accessories such as printers and network hubs can be supported, although care is needed in handling laser printers which can cause harmonic distortion on the UPS output. Some of these UPS systems are available with compact, office-friendly designs in either PC Tower or 19” rack-mounting versions. At the higher power ratings, these systems may be permanently installed using three-phase inputs and possibly supplying three-phase outputs. Many manufacturers will facilitate extra battery capacity by offering visually compatible add-on battery cabinets, allowing complete, aesthetically appealing UPS systems to be installed into an office environment.

Office-specific functionality

Batteries are often more of an issue for a small office system than a data centre, large enough to support an on-site generator backup system. During an extended power blackout, the data centre can be switched to generator power if the UPS battery autonomy is threatened. Without such generator access, the smaller system must rely on the UPS battery autonomy to stay online; accordingly investment in extra battery cabinets to provide a backup time of several hours may be considered desirable. Alternatively, if the load is less critical, a policy of using the battery autonomy to facilitate an orderly shutdown may be acceptable.

These smaller systems can offer the same flexibility and reliability as their larger data centre counterparts. Some comprise fully modular designs with no single point of failure. UPS capacity can be incremented by, say, 1.25kVA at a time by plugging in UPS power boards, so N+1 redundant systems can be configured with minimal excess UPS overhead and cost. This also allows great flexibility, because if the office requires more workstations, they can be accommodated simply by plugging in extra UPS capacity. As an alternative arrangement, some systems can be paralleled for extra capacity or redundancy using a CANbus interconnection.

Smaller systems today also address another issue of great importance to all users – energy efficiency. High efficiencies of well over 90% at 100% load are available, together with near-unity power factors and low input current THDi regardless of load.

Divergence from the data centre environment is not just about scale. Day to day operation of the UPS equipment will have to be managed by office staff if the site does not warrant a permanent IT or UPS specialist. As many of these UPS systems are located next to or at least within close proximity to the equipment they support, their task will be eased by user-friendly front panel mounted displays. These should reveal major system parameters and current status, including load level, battery level, system wiring faults, overload and programmable output status. For the larger systems, remote alarms, diagnostics and control should also be possible using status contacts, serial or network communications.

Whether rack-mounted or in a PC tower format, the systems should be compact as space may be very limited. They should also operate in conditions, which differ from those found in a dedicated data centre regarding size ad environment. Cost, space and environmental considerations will probably preclude the installation of a generator for use in extended blackouts.


In this article we have seen how many IT users depend on smaller office systems rather than large-scale data centres, yet their needs for continuous IT availability are just as critical. Along with this, though, we have looked at UPS manufacturers’ ability to offer suitably profiled solutions – not just by scaling down, but also by offering functionality appropriate to the needs of these smaller environments.

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