Operation
900-0167-01-00 Rev A
43
Multiple-Inverter Installations (Stacking)
Multiple inverters in a single system can support larger loads than a single inverter. Installing inverters
in this configuration is called “stacking”. Stacking refers to how inverters are wired within the system
and programmed to coordinate activity. Stacking allows inverters to work together as one system.
Each inverter is programmed to power an individual phase of the system and to operate at certain times.
This order is assigned using a system display such as the OutBack MATE3. FXR stacking includes “series”
(split-phase), “parallel” (single-phase), “series/parallel” (split-phase) and “three-phase” configurations.
Each inverter needs to be assigned a status — “master” or “slave”. The master provides the primary (L1)
output. “Subphase” masters provide the output for other phases in series or three-phase systems.
Slave inverters provide assistance when a master on any output cannot power the loads alone. See the
FXR Series Inverter/Charger Installation Manual
for more information.
Stacking requires an OutBack HUB10.3 Communications Manager and CAT5 non-crossover cable. The
HUB10.3 has designated assignments for each of its ports. The inverter on each port is programmed with
a status and stacking value. There are usually other specialized instructions during installation.
An AC source for a split-phase or three-phase system should provide input to all inverters on all
phases. A slave inverter will give a
Phase Loss
warning if it is not supplied. (See pages 31 and 63.)
If
Coordinated AC Connect/Disconnect
is enabled, the source
must
provide input to all phases. If any
phase is not supplied, all inverters will disconnect. See pages 21 and 32 for more information.
Figure 10
OutBack HUB10.3 and MATE3
IMPORTANT:
The master inverter must always be connected to Port 1 on the HUB product. Connecting it
elsewhere, or connecting a slave to Port 1, will result in backfeed or output voltage errors
which will shut the system down immediately.
All stacked FXR inverters must have the same firmware revision. If inverters are stacked with
different firmware revisions, any unit with a revision different from the master will not
function. The MATE3 will display the following message:
An inverter firmware mismatch has been detected. Inverters X, Y, Z
3
are disabled. Visit
www.outbackpower.com
for current inverter firmware.
FXR-class inverters cannot be stacked with FX-class inverters. If more than one model class
or series is stacked, any inverter different from the master will not invert or connect to an AC
source. The MATE3 will register an Event in the log. It will display the following message:
A model mismatch has been detected. Inverters are incompatible. Inverters X, Y, Z
3
are
disabled. Match all models before proceeding.
Installing multiple inverters without stacking them (or stacking them incorrectly) will result
in similar errors and shutdown.
Although stacking allows greater capacity, the loads, wiring, and overcurrent devices must
still be sized appropriately. Additional terminations or bus bars may be required.
Overloading may cause circuit breakers to open or inverters to shut down.
3
The port designations for the mismatched inverters are listed here.
Additional Ports
Port 1
MATE
HUB10.3
Communications
Manager
MATE3
System
Display
