ns,
I agree that it is defective and have removed it from service. My reasons for asking were:
1. I was wondering if Backfeeding was a common result of some particular component failure within the UPS. If so, (it was an older unit) have newer units been equipped with some provision to prevent this from happening?
2. And should the UPS units within a facility be suspected and tested as part of a search for unexplained power quality fluctuations?
