Artesyn Centellis 2000 Shelf - DC Installation and Use (June 2014) - Manual (Page 84)

System Installation
Centellis 2000 Shelf - DC Installation and Use (6806800G45F) 84
15.Check the PEM LEDs and take the appropriate actions as listed in the table below.
16.Push the breaker to the ON position.
The BP LEDs (on the right) indicate that power is available to the backplane from
the feed.
PEM LEDs Status
Reverse LED (red) on
In LED (green) off Do not switch on the breaker while the Reverse LED is on.
Reason: The power connected is reverted.
Action: Turn off the feed power and attach the power cables at the
power connector with the correct orientation (-48 V, Return).
Reverse LED (red) off
In LED (green) off Do not switch on the breaker while the In LED stays off.
For possible reasons and solutions, see
Appendix A, After Power On .
Reverse LED (red) off
In LED (green) on The power is connected correctly. You may switch on the breaker now.
PEM Damage
Applying reversal power causes damage to the electrolytic capacitors of the filter.
Therefore, only switch on the breakers if no red light is visible.