Dell EMC ME4 Series Owner's Manual page 72

Before removing the PSU, disconnect the power from the PSU by either the mains switch (where present) or by physically removing the
power source in order to ensure your system has warning of imminent power shutdown. Ensure that you correctly identify the faulty PSU
before beginning the step procedure.
1 Stop all I/O from hosts to the enclosure. See
NOTE: This step is not required for hot-swapping. However, it is required when replacing both PSUs at once.
2 Use management software to shut down any other system components necessary.
NOTE: This step is not required for hot-swapping. However, it is required when replacing both PSUs at once.
3 Per Figure 8. 2U12 enclosure system—front panel
disconnect the power supply cable.
4 If replacing a single PSU via hot-swap, proceed to step 6.
5 If replacing both PSUs, verify that the enclosure was shut down using management interfaces, and that the enclosure is powered off.
6 Verify that the power cable is disconnected.
7 Refer to Figure 59. Removing a PSU (1 of 2)
a Push the release latch to the right and hold it in place (detail No.1).
b With your other hand, grasp the handle and pull the PSU outward (detail No.2). Supporting the PSU with both hands, remove it
from the enclosure. See
Figure 59. Removing a PSU (1 of 2)
Figure 60. Removing a PSU (2 of 2)
8 If replacing both PSUs, repeat steps 5 through 7.
NOTE: The PSU slot must not be empty for more than 2 minutes while the enclosure is powered.
72 Module removal and replacement
Shutting down a controller
components, verify the Power OK LED is lit, then switch off the faulty PSU, and
when performing this step:
Figure 59. Removing a PSU (1 of
module.
2).