NEC 140He User Manual page 271

4.
If you are not going to install a replacement power supply unit, you must install a blank cover you removed in
step 2 of installation procedure to vacant slot.
IMPORTANT:
vacant slot of the power supply bay.
5.
Install the new power supply unit taking steps 3 to 6 of "Installation", and confirm that the power supply unit
is installed normally.
NOTE:
If one of the three or four power supply units of the server is replaced while the
power is on, the POWER lamp of the new power supply unit goes on. (If it is replaced
while the power is off, the lamp goes on after the power is turned on.)
To maintain the cooling effect in the server, install the blank cover in the
9-13