Outback Radian AC Coupling Note

Application Note

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Once PV production is gone for the day, then the Radian inverter will power the loads in the backup

mode until sun returns the next day, or the battery bank reaches low battery cutout (LBCO). If the

battery bank reaches LBCO, then the Radian inverter can no longer power the backed up loads or be a

voltage source for the GTI to start again and recharge the batteries.

To recover the batteries, either an AC generator, or a DC charging source must be connected to the

battery bank in order for the system to recover, and begin AC coupling PV power through the GTI again.

Use caution when connecting an AC generator; there is risk that the GTI may backfeed the AC generator

and cause catastrophic failure. To avoid damaging the generator and/or voiding the GTI warranty, two

possible generator solutions are discussed after the Solution section below.

Solution

The Radian inverter is limited to a maximum of 25 Aac GTI load current at 240 Vac which means a 6kVA

GTI is the maximum that can be connected. However, the Radian Frequency Shift solution does support

stacking up to three Radian inverters in parallel.

Programming the Radian is a fairly simple task. The Absorb, Float and SellRE, and AC Charger Input

settings that are used by the AC Coupling function, are programmed as explained in the Radian

Operator’s Manual and battery charging applications notes. The new AC Coupling function is located in

the MATE3s Inverter menu, but is only accessible after entering the Installer password. Programming

steps are described below.

IMPORTANT:

 Radian AC Coupling firmware version 1.6.70 must be downloaded from the

OutBack website and installed.

 A MATE3s system display with firmware version 1.4.1 or newer is required for

AC Coupling operation.

 Previous OutBack system display products (MATE, MATE3) cannot be used

for this operation.

Setting up the AC Coupling function with the OutBack Radian inverter requires a connection between the

Radian and the GTI. While the connection could be made in the Backup Load Panel, it is best to use the

Radian GSLC load center so that a disconnect can be installed and easily accessed if the GTI needs to

be quickly disconnected or an overload condition should arise. OutBack Power has a 30 Aac panel

mount circuit breaker compatible with the GSLC that can be used as a disconnect. This connection is

show below in Figure 6. Alternatively, if an over current protection device (OCPD) already exists in the

output circuit of the GTI, then the GTI connection could be made directly from the GTI OCPD to the

Radian AC output bus bar.