PROS: Can be used to double the output of a UPS and can be a cost effective method when paralleling for capacity.
Ex: Two 50kva UPS can be paralleled for a total output capacity of 100kva.
CONS: Not a very reliable means of redundancy. In an event that one unit unexpectedly transfers to a bypass source, the
remaining unit can potentially be back-fed by the bypass source resulting in cleared fusing or internal damage. This is
because the bypass source is typically a stiffer source of commercial A/C power.
Modular Systems in Parallel: (Also known as an N+1) Modular systems are designed to provide a low cost
solution with the reliability of a redundant system, however this design falls short. Their inherent design
doesn't contain the same type of de-rated components as an independent or stand alone UPS. The low
reliability of each individual module requires them to be designed in parallel configurations in case of a
single failure. This in turn, reduces their overall MTBF, and while the initial cost of a modular system may be
less, the cost of ownership and risk of premature failure is much higher.