Load On Bypass; Ok To Transfer; Figure 52 Load On Bypass, Ups Not Available - Liebert 1000kVA Operation & Maintenance Manual

3.3.1

Load on Bypass

Load on Bypass, with the UPS not available, is shown in Figure 52. The UPS system could be in this
mode of operation during either initial start-up or UPS system shutdown and isolation for mainte-
nance.
NOTE
When the critical load is being supplied power from the bypass line, it is exposed to utility
power disturbances.

Figure 52 Load on bypass, UPS not available

UPS
CB1
CB2
MBD
Battery
3.3.2

OK to Transfer

The OK to Transfer status message will be displayed when the bypass line and UPS system output
power are both available, their voltage, frequency and phase synchronization are matched within
specifications and the Static Switch Disconnects are closed (ON). An alarm message may be displayed
to indicate Load On Bypass. If no alarm is displayed, the operating status is Load On UPS.
When the OK to Transfer message is displayed, you can perform a manual transfer of the load from
the UPS system to bypass or a manual retransfer of the load from bypass to the UPS system.
Use the Load Transfer Procedures screen at the SCC when performing a manual transfer. Refer to
3.4.3 - Load Transfer Procedures.
The UPS system control logic at the SCC will initiate an automatic transfer to bypass if an overload
condition exceeds the system current versus time window or if a UPS module is taken off line while
the system is operating in the non-redundant mode. An automatic retransfer to the UPS system may
be initiated when recovering from system overloads lasting less than five minutes. Refer to 3.5 -
Automatic Operations.
NOTE
When the critical load is being supplied power from the bypass line, it is exposed to utility
power disturbances.
RIB RIB
#3 UPS #2
CB1
R R
I I
CB2
MBD
Battery Battery
RIB
UPS #1
CB1
SBS
R
SBB
I
System
CB2
Controls
Output
SCCT
MBD
(can accommodate up to 6 UPS modules)
74
Operation
BFB
BIB
MBB
SKRU
MIB
To Critical Load
SCCT