HP procurve switch zl Installation Manual page 12

Installing the Power Supply
6
3. Tighten the four retaining screws that hold the power supply in place
until the screws are secure, as shown in the next illustration. The screws
can be tightened with either a flat-bladed or Torx T-10 screwdriver. Be
careful not to overtighten the screws.
Figure 4. Fully installed power supply
4. Connect the power cord supplied with the power supply to the power
connector, and then into a properly grounded electrical outlet. To provide
true redundancy, the second power supply should be connected to a
different AC power source from the other supply. Then, if one AC power
source fails, the switch will continue to run.
Tighten the four screws