Outrageous as it might sound, placing an independent uninterruptible power supply (UPS) at each end of a datacom or telecom system to secure totally redundant backup power may likely become the rule rather than the exception.

Indeed, these so-called 2N systems, also known as the dual-independent backup, are a rising trend that is coming to be recognized as the latest paradigm shift in how UPSes are applied.

The strategy of using one UPS to feed another in a mains-bypass architecture (also called an isolated-redundant scheme) has been employed for some time in the most critical three-phase megawatt-level systems. However, in the past year or so, the 2N system concept has arrived and is coming down faster to the 50 kVA-and-below server and industrial areas. It's designed to buy 100 percent up-time, at least hypothetically.

Driven by the end user even during the economic downturn, the 2N architecture is appearing more in systems for which reliable operation is critical.

Just a few years ago, it was all the rage to see hot-swap modules and redundant battery backup in a given UPS to increase the mean time before failure (MTBF). "The five-nines [keeping the system up for 99.999 percent of the time] and MTBF have been replaced by 100 percent availability," notes Liam McPartland, director of national accounts for MGE UPS Systems (Costa Mesa, Calif.).

Indeed, mention of five-nines reliability is becoming much less frequent as the powerbackup challenges become more stringent. For more systems, it's a case of absolutely, positively never going down. Basically, the way to do that is to distance all the power backup parts from each other and count on them not to fail at the same time. "The real point of such a system is to allow us to perform preventive maintenance," said Henry Lengefeld, senior staff engineer at American Power Conversion (West Kingston, R.I.).

At this point the total cost to the user for a 2N is still essentially twice the cost of a single UPS.

As in most areas, the most successful vendors will be those who provide more for less. "The key to implementing the dual UPS lies in a scalable building-block approach and [being successful at] volume production," Lengefeld said.