Transfer From Maintenance Mode To Normal Mode - Emerson Liebert APM 90 User Manual

40 Chapter 5 Operating Instructions
Before performing this operation, read the messages on the LCD to be sure that bypass supply is normal and the
inverters are synchronous with it. If these conditions are not present, there is a risk of a short interruption in powering
the load.
1. Press and hold the INVERTER OFF key on the right side of the operator control and display panel for two
seconds.
The inverter indicator turns off, the status indicator turns yellow and an audible alarm sounds. The load is
transferred to the static bypass and the inverters turn off.
Pressing the SILENCE ON/OFF key cancels the audible alarm, but leaves the warning message displayed until the
appropriate condition is rectified.
2. Close the maintenance switch Q2. The load is now on maintenance bypass.
If you need to maintain a faulty module, wait about 10 minutes for the internal DC bus capacitors to discharge before
removing the faulty module.
3. Open the input switch Q1 and output switch Q3.
1. The load is not protected from normal supply aberrations when the UPS is operating in maintenance mode.
2. After the UPS is transferred to maintenance bypass, the power modules and bypass module are inoperative and the
LCD has no display, only the green indicator of the input SPD shows the UPS has mains input, but the output terminals
corresponding to closed output distribution switches and the neutral bars are energized.

5.3.5 Transfer From Maintenance Mode To Normal Mode

The following procedures will transfer the UPS from maintenance mode to normal mode.
1. Open the front door of the cabinet and close the input switch Q1.
2. Close the output switch Q3.
3. Wait until the LCD screen starts up, switch the display to the Event men and confirm that Bypass mode is
displayed.
The bypass must be started before the maintenance switch is opened. Or else, the load power will be interrupted.
4. Open the internal maintenance switch Q2.
5. Wait until the rectifier indicator begins to illuminate green constantly, press and hold the INVERTER ON key
for two seconds. Then the inverter starts, and the inverter indicator begins to blink green. After the inverter
enters normal operation, the UPS transfers from bypass mode to normal mode, and the inverter indicator
begins to illuminate constantly.
At the moment, the load has been transferred to the inverter supply
Liebert APM 90 Integrated Modular UPS User Manual
Caution
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Warning
Caution
Warning