Juniper MX2020 Hardware Manual page 404

WARNING:
To ensure that all power is off, locate the circuit breaker on the panel board that
services the AC circuit, switch the circuit breaker to the off position, and tape the
switch handle of the circuit breaker in the off position.
CAUTION:
power supply unit, each PDM slot must contain either a PDM or a blank panel. If you
remove a PDM, you must install a replacement PDM or a blank panel shortly after the
removal.
NOTE: After powering off a PDM, wait at least 60 seconds before turning the circuit breaker
back on.
NOTE: The PDMs are hot-swappable in a redundant configuration. However, you cannot switch
from one type of PDM (AC or DC) to another while the system is on.
Each single-phase AC PDM weighs approximately 9 lb (3.6 kg). To remove a single-phase AC PDM:
1. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to
one of the ESD points on the chassis.
2. Move the switch to the off (O) position for the power supply modules that are powered from only the
AC PDMs being removed.
NOTE: After powering off a PDM, wait at least 60 seconds before turning it back on.
3. Remove the two thumb screws at each end of the power cord retainer by turning them
counter-clockwise.
4. Remove the power cord retainer.
5. Starting at one end of the PDM, unplug all the power cords.
Before performing AC power procedures, disconnect all power sources.
To maintain proper cooling and prevent thermal shutdown of the operating
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