Section IV
Multiple UPS Configurations
006-0006205
UPS-1500 Series
Rev ZC
41 of 60
05/28/2019
Either connection scheme is acceptable, as long as the resultant input voltage falls within the
specified range of the AC INPUT of the individual UPS units.
If the AC OUTPUTS of the three UPS units are connected in parallel, they will automatically share
the total load power equally. Therefore, the power that they each draw from their respective
AC INPUT phases will be balanced with each other. If, on the other hand, the three UPS units
have their AC OUTPUTS connected in a manner to create a 3-Phase AC OUTPUT, then the power
flowing through each UPS, and therefore the power drawn from each AC INPUT phase, will
depend on the load power drawn from each AC OUTPUT phase. This load power may or may not
be balanced.
Multi-unit AC Output On/Off Control – Standard Parallel (-F option)
In multi-unit operation, all combined front panel “on” switches must be actuated before any
AC output will turn on. Any “off” front panel switch actuation will cause all AC outputs to turn
off. In addition, the “remote-on” or “remote-off” rear panel signal inputs may be utilized for
coordinated AC output on/off control. If any single UPS no longer has a valid input power source
(e.g., no AC or DC input and depleted battery), the combined AC output will shutdown.
Multi-unit AC Output On/Off Control – Expanded Parallel (-R option)
For expanded parallel multi-unit operation, any “on” front panel switch actuation will cause all
AC outputs to turn on at once. In addition, the “remote-on” rear panel signal can be used for a
coordinated start.
Any “off” front panel switch actuation will cause that specific unit be deactivated. All other units
will continue to function, assuming the load can be supported with one less unit. In addition, the
“remote-on” or “remote-off” rear panel signal inputs may be utilized to enable and disable one
specific unit.
For coordinated shutdown, the user must send “SYSTEM DISABLE” over RS-232. See Section VI of
the Owner’s guide for details on the RS-232 interface. See UPS Terminal Commands document
for more information on the “SYSTEM DISABLE” command.
AC Output Neutral Grounding
UPS units combined in multi-unit configurations must have the neutral floating “F” factory
option to prevent the possibility of circulation protective earth currents. Expanded parallel
units (“R” option) come with a floating neutral wire by default. If a grounded output neutral
is required, then the output neutral should be connected to protective earth ground (PEGND)
in one spot. The size of the neutral-to-PEGND connecting conductor must be sized to match
the largest combined AC output neutral conductor specified in the wiring diagrams above.