NonStop NS2200 Series Planning Guide

Once the downstream UPS is in this state, it still might not immediately perceive stable input power.
The downstream UPS is thus compromised until it achieves a lock on stable input power and is
able to recharge its batteries.
Such problems are very difficult to predict. Their occurrence is a function of the output characteristics
of the primary UPS, the input characteristics of the downstream UPS, and the load characteristics
of the other devices deriving power from the upstream UPS. Factors can include the other types of
loads which are driven by the upstream UPS. Some non-linear loads such as lighting or larger
motors are more likely to distort the upstream UPS output than other electronic equipment.
The occurrence of these problems is unpredictable and has affected NonStop customers. There is
currently no known method to analytically predict the occurrence of such instability. To ensure
correct UPS function, HP recommends that you conduct on-site system testing and that you try to
use the supported UPS configurations described in this appendix.
Non-Supported UPS Configurations 209