4.4 UPS PARALLELED ON THE SAME BATTERY
NOTE !
A Parallel System with a Common Battery for two or more UPS (max. 4 units), requires
a particular installation and adequate setting of some parameters, (accessible only
through password), and can therefore only be done by a GE QUALIFIED ENGINEER.
Usually each UPS Unit runs with its own Battery.
In case of parallel units running with a Common Battery (max. 4 UPS - see Fig. 4.4-1), the sharing circuit
between the individual UPS is integrated in the communication bus of the system in order to assure an
equal sharing of the Rectifiers output currents.
Fig. 4.4-1 Diagram RPA system with UPS on Common Battery
1 –
2 –
3 –
4 –
5 –
6 –
7 –
Rectifier
Inverter
Automatic Bypass
Utility Input
Load Bus Bar
External Battery Fuse
External Battery
Pay attention to the following recommendations:
• The units delivered for this functioning mode needs special parameters setting, so they must be
prepared in advance before the installation.
• The installation must be performed only with the UPS system completely shut down.
• The AC Rectifiers input power (4) must be the same, with clockwise phase rotation for each unit.
• Each Rectifier must be set for the same floating DC voltage and the same Battery current limitation.
• It is mandatory to install the fuses / MCB (6) on each line connecting the Rectifiers to the common
Battery for maintenance / safety reasons (see Installation Guide to Section 4.8.2).
• In case a unit must be powered down for maintenance, switch-OFF the concerned unit before open
the DC fuses / MCB on the Battery line (6).
• It is recommended to connect an external NO free contact “Battery Fuses” to the UPS and to enable
the function by setting the parameter (see Section 9.1).
• If an emergency generator set supplies the UPS, and the free contact “Generator ON” is connected
to the Customer Interface, connect a separate NO free contact on each parallel unit.
• The parameters enabling the Battery test, both manual and automatic, must be set in the same
mode on all the units sharing a Common Battery.
• Do not connect the temperature sensor for automatic battery floating voltage compensation.
• Do not enable the function Boost charge.
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