This operation will make the load transfer from UPS power supply protection state to direct connection with AC input bypass
state.
CAU TIO N : Pow er supp ly interruption can cause danger of the load. Before perform ing this
procedure, ch eck the LCD inform ation first, and m ake sure the bypass is n orm al and inverter
synch ronized. O therw ise, it m ay result in the load pow er interruption for a while.
1. Manually turn off the inverter of each UPS in turn. The power flow diagram shows INVERTER OFF, and the
buzzer alarms. The load transfers to the static bypass, and the inverter shuts down. At last, all UPSs are
transferred to Bypass mode.
N O T E: Pressing the SILE N C E OFF button can silence the alarm , but the alarm m essage on the
touchscreen does not disappear until the alarm status is cleared.
2. Close the UPS external total maintenance bypass switches, and do not close the internal maintenance bypass
switch Q3 of each UPS.
3. At this moment, the external total maintenance bypass should be parallel connected with each UPS's static
bypass.
4. At this moment, the touchscreen of each UPS displays ' Maint. Switch Closed'.
5. Disconnect the output switch Q5 of each UPS in turn, and the maintenance bypass can supply power to the load.
CAU TIO N : Load is not secured on the maintenan ce bypass an ym ore unless there is pow er
generator running instead of norm al grid u tility.
6. Pressing the EPO button of each UPS stops the operation of rectifier, inverter, static switch and battery, but this
action will not affect the maintenance bypass to power the load normally.
N O T E: In m ainten ance m ode, the load is directly fed by the m ains pow er in stead of the pure A C
pow er from the in verter.
7. Disconnect the rectifier input switch Q1 and bypass input switch Q2 of each UPS in turn.
At the moment, all the internal power supply is off and the touchscreen does not display any more.
W ARN ING ! If the m aintenance is requ ired, wait 10 m inutes for the internal DC bu s capacitance
discharging.
W ARN ING ! T he p arts of U P S circuits also have hazardous voltage, though the rectifier input
sw itch, bypass in pu t sw itch and battery sw itch are disconnected. Therefore, the UP S
m aintenance is applicable to q ualified personn el only.
8.3.3 Procedures for Isolating One UPS module from Parallel System
IM PO R T A N T ! These pro cedures shall on ly be carried ou t by service p ersonnel of Vertiv or und er
their guidan ce.
8 Parallel System and LBS System
134
Vertiv™ Liebert® APM Plus User Manual
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