Outback FX-R Series Installation Manual

Commissioning
900-0166-01-01 Rev A 31
Multiple-Inverter AC Installations (Stacking)
Installing multiple inverters in a single AC system allows larger loads than a single inverter can
handle. This requires “stacking”. Stacking inverters refers to how they are wired within the system
and then programmed to coordinate activity. Stacking allows all units to work together as a
single system.
Examples of stacking configurations include “series”, “parallel”, “series/parallel”, and “three-phase”.
Figure 22 OutBack Communications Manager and System Display
Each inverter must be assigned a stacking mode, “master” or “slave” of some type depending on
the configuration.

The master inverter provides the primary output phase, L1 (or Phase A in a three-phase system).
Other inverters in the system base their phase on that of the master inverter. If the master shuts off, all
other inverters also shut off. The master must sense and connect to an AC source before other inverters
can connect.
~ In a parallel-stacked system, the master tends to be the most heavily used unit.
~ “Subphase master” inverters are used to control other phases in series or three-phase systems.
A subphase master inverter operates semi-independently of the master inverter. Although the
master inverter sets the phase relationship, the subphase master creates an output independent of
the master.
~ The master on the L1 (or A phase) output cannot measure loads and voltages on any other output.
The subphase masters for each of the other outputs perform monitoring and regulation for the phase
they control.
~ In a series or series/parallel-stacked system, a subphase master is required for the L2 output.
~ In a three-phase system, subphase masters are required for both the B and C phases.

A slave inverter does not create an independent output. It simply assists the master or subphase master
by adding power to the output as needed.
~ The Power Save function can place slave inverters in “Silent” mode when not in use. They are
activated by the master or subphase master when required.
NOTE
:
The FW-X240 and similar transformers are not used for load balancing of stacked
FXR inverters.
MATE3s
System Display
Stacking Connections
Stacking requires an OutBack HUB10.3 communications manager and a system display.
Make all interconnections between the products with CAT5 non-crossover cable.
Additional Ports
Port 1
MATE
Port
HUB10.3
Communications
Manager