I've found at my new job that my boss has configured his server cabinets (4)
each with two UPS, daisy-chained together. Nothing but a UPS is plugged into
the first, and then all the load is placed on the last (identical) UPS. He
thinks get double the run time.

I made some negative comments, but ultimately was unconvincing.

I found this at www.APCC.com:

4) In most cases, daisy-chaining UPSs does not allow for extra run time. If
you are using a UPS that outputs a step-approximated sine wave when on
battery, as soon as the fist UPS goes on battery, the second UPS will also
go on battery because it will see the step-approximated sine wave as
distorted or bad power. Both units will discharge together, and will not
provide any extra run-time to the load.

http://tinyurl.com/clvxd
(http://nam-en.apc.com/cgi-bin/nam_en...php?p_faqid=39
7&p_created=1010390400&p_sid=5O4PodXh&p_lva=&p_sp= cF9zcmNoPTEmcF9zb3J0X2J5PS
ZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9MTAmcF9wcm9kcz0wJnBf Y2F0cz0mcF9wdj0mcF9jdj0mcF
9zZWFyY2hfdHlwZT1hbnN3ZXJzLnNlYXJjaF9ubCZwX3BhZ2U9 MSZwX3NlYXJjaF90ZXh0PWRhaX
N5IGNoYWlu&p_li=&p_topview=1)

Can any of you smart people validate or expand on why we should not be
daisy-chaining UPSs together?

Thanks

:O:
wd