Operation
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.
The Radian inverter can be stacked in parallel to increase capacity. Up to ten units can be stacked to operate in a single system. Each inverter is programmed to operate at certain times.
Stacking requires an OutBack HUB product, as well as a MATE3 system display (sold separately). 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
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 MATE3 to assign a status and stacking value to the inverter on each port. See the MATE3 and HUB manuals for programming instructions.
HUB4
Additional Ports Port 1 MATE Port
MATE3
Figure 6 OutBack HUB4 and MATE3
IMPORTANT:
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.
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 and bus bars may be required. Overloading may cause circuit breakers to open or the inverters to shut down.
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