Working in parallel

Power Control
18 Dec 2018

In the event of a power outage, an uninterruptible power supply (UPS) provides critical power to protect business continuity. The reliability of which is largely dependent on the configuration of the UPS solution. In order to achieve a high level of reliability a degree of redundancy should be incorporated.

Not only does redundancy reduce the number of single points of failure, but it also allows for future business expansion, something all businesses should plan for. Installing a capacity configuration will keep initial costs to a minimum, however, consistently running a UPS at 100% does not allow for a load inrush surge, a common occurrence when multiple applications are booted up at the same time, nor does it provide a margin for error.

Designed to increase capacity or UPS availability, a parallel redundant, or N+1, configuration comprises of two or more UPS units connected in parallel and running off common components. Each unit should be sized to be capable of supporting the entire load if required, however, in normal operating conditions should be running at no more than 70% capacity. This provides a level of redundancy and allows for the failure of one UPS unit within the configuration without putting the critical load at risk. The remaining units will automatically resume full load, enabling the damaged unit to be isolated and repaired.

As a scalable configuration, this design is commonly found in large business environments to increase reliability and ensure flexibility. The number of UPS systems that can be paralleled into a common bus is often left to the discretion of the UPS manufacturer. It is important to note however, that the UPS systems used in a parallel redundant configuration must be the same model and capacity, and from the same manufacturer.

Whether it be two UPS systems in parallel or ten, the increased fault clearing capabilities of a parallel redundant configuration ensures that short circuits are cleared twice ass efficiently without having to transfer the load to the bypass, avoiding unnecessary switching or tripping of supply switchgear.

The simplicity of the design and the ease of expansion allows for uncomplicated maintenance and makes it a cost effective and efficient total cost of ownership (TCO) UPS solution.

For more information on UPS design configurations, please download our technical ‘UPS Design Configurations’ whitepaper.

Alternatively please visit, email or call the office on 01246 431431 for all other critical power information.