NEC Storage S1300 User Manual page 26

When inserting the power supply unit into the disk array unit, push it
as far as it will go and then secure it with the screw. Incorrect
insertion may cause a power supply failure.
When replacing a power supply, prepare the new power supply before removing the old
one, and then replace it within about 3 minutes. Disk drives, power supplies and
controllers generate heat within the disk array unit. The fans in the power supplies
ensure proper cooling of all of these components. Therefore, do not leave the disk array
unit with one of the power supplies removed. Doing so causes the disk drive
temperature to rise, which may significantly decrease the system reliability. If the power
supply is removed for longer than five minutes, the system executes the shutdown
sequence.
1-8 System Overview
CAUTION