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900-0112-01-00 Rev B 25
Multiple-Inverter Installations (Stacking)
Multiple inverters in a single system can support larger loads than a single inverter can handle.
Installing inverters in this configuration is called “stacking”. Stacking inverters does not refer to
physically placing one on top of another. It refers to how they are wired within the system and then
programmed to coordinate activity. Stacking allows all units 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 MATE or MATE3. (Stacking
the GFX inverters requires a MATE with firmware revision 4.1.6 or above.)
Examples of stacking configurations include “parallel” and “three-phase” configurations.
Stacking requires an OutBack HUB product, as well as a system display. A system of four or fewer units
may use the HUB4. Systems of up to ten units require the HUB10. All interconnections are made using
CAT5 non-crossover cable. (See the International Series GFX Installation Manual for more stacking
instructions.)
Each inverter needs to be assigned a status — “master” or “slave”. The master is the primary and most
heavily used unit. Slave inverters provide assistance when the loads are more than the master can
handle alone. Programming involves using the system display to assign a status and stacking value to
the inverter on each port. See the system display and HUB manuals for programming instructions.
Figure 7 OutBack HUB4 and MATE
IMPORTANT:
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The master inverter must always be connected to port 1 on the HUB. 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.
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Installing multiple inverters without stacking them (or stacking them incorrectly)
will result in similar errors and shutdown.
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Although stacking allows greater capacity, the loads, wiring, and overcurrent
devices must still be sized appropriately. Additional terminations and bus bars
may be required. Overloading may cause circuit breakers to open or the inverters
to shut down.
CAUTION: Equipment Damage
The inverters in a stacked system should all be the same DC voltage, wattage, and
model. Do not stack inverters of different wattages.
Additional Ports
Port 1
MATE Port
HUB4 MATE