Installation
32 900-0113-01-00 Rev A
Three-Phase Stacking

In three-phase stacking, inverters are stacked to create three separate 120 Vac output legs in a wye

configuration.

The output of each inverter is 120° out of phase from the others. Any two outputs produce 208 Vac
between them. The outputs can be used to power three-phase loads when all inverters work together.
Only three inverters, one per phase, may be installed in a three-phase arrangement.
1.3 kVA 120 Vac
1.3 kVA 120 Vac
1.3 kVA 120 Vac
1.3 kVA
120 Vac
3.9 kVA
208 Vac
1.3 kVA
120 Vac
1.3 kVA
120 Vac

Figure 24 Example of Three-Phase Stacking Arrangement (Three Inverters)

When installing a three-phase system, the following rules must be observed.

Three-phase stacking requires a system display and a HUB.
The inverter that is mounted physically lowest is always the master and is programmed as Master. (See the
system display manual for programming.) Mounting below the other inverters allows the master to avoid
heat buildup and remain relatively cool, as it sees the greatest duty cycle.
The master must be connected to port 1 of the HUB. Other inverters must not be selected as master.
One slave inverter must be programmed as 3p Classic B. The other must be programmed as 3p Classic C.
(See the system display manual for programming.)
The inverters should be wired to loads, and to AC sources, in phase order. The master should be phase A,
the first slave should be phase B, and the second slave should be phase C.
All inverter wiring and input breakers must be sized for 60 Aac or less.
All inverters must be of the same model.
The AC input (generator or utility grid) must be 120/208 Vac at 60 Hz (a three-phase wye configuration).
When wiring the AC source to the inverters, local codes may require the inverter breakers to be located at
the bottom of the main panel. This prevents overloading of the AC bus.

IMPORTANT:

Although the HUB manual states that it is necessary to move the HUB’s jumper to the
three-phase position, that statement is not applicable for this model. The jumper must
be left in its original position.