Outback FX-R Series Technical Note on Input Modes

Application Note

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surplus PV power being generated during this time can be stored in the OutBack grid/hybrid

inverter’s battery bank for use at a later time.

The OutBack MATE3 has up to three grid use timers for weekdays and one grid use timer for

the weekend. The Use and Drop settings determine the actual connection times to the grid. The

Use period defines the beginning time of the grid connection. The Drop setting determines the

time at which the critical load panel running from the OutBack inverter is disconnected from the

grid and uses the batteries to power the loads. Any other grid-connected load panels not

connected to the output of the OutBack inverter will continue to run from the grid and will not be

affected by this function.

The Grid Use example in Figure 4 shows the power will get dropped at 6am, reconnected at

9am, dropped again at 4pm (16:00), and then reconnected again at 9pm (21:00). This will keep

the loads connected to the critical load panel at zero consumption from the grid during 6-9am

and 4-9pm when TOU charges are highest. Note that the third weekday and weekend timers

have been disabled by setting both the Drop and Use times to midnight (0:00), but could also be

enabled to add yet more time periods to be off-grid and continue savings from TOU charges.

LIMITING PEAK DEMAND CHARGES

Utilities need to provide maximum power capacity equal to the worst-case scenario where all

their customers were to be demanding power to their highest peak that would occur in a month.

This usually happens during the typical peak demand times in the morning or afternoon, but

many utilities will calculate their peak demand charges to the largest 15-minute peak load

demand for each of their utility customers whether it occurred during the peak demand times or

not and is usually on top of time of use charges if they also apply. In some cases only

commercial customers are charged an additional peak demand charge.

If you are paying peak demand charges, there is a mode of operation with OutBack inverters

that will allow you to reduce it. This input mode is called Support. The incoming power from the

grid can be set to a maximum limit, then supported with DC power from batteries and PV to

meet the rest of the load demand. For example, if the incoming utility current limit is set to 15

amps and the electrical load in the house increases to 25 amps, then 10 amps from the battery

bank would be blended with the 15 amps of utility power to satisfy the 25 amp load demand.

This blending of grid power with DC power is also a form of the Offset function, but the trigger is

the AC Input Current Limit setting whereas Offset in the other input modes uses one of the

battery voltage charging targets (Equalize, Absorb or Float) or the Sell RE voltage setting for its

trigger to blend grid power with DC power.

OPTIMIZING SELF CONSUMPTION OF RENEWABLE ENERGY

While the Grid Tied input mode will self-consume available PV with any excess being exported

to the power grid, and Grid Use Timers can self-consume PV power on demand for any given

time slots during the day, the Grid Zero and Mini Grid Input Modes more fully optimize self-

consumption without any PV power going to the grid or otherwise become stranded on the

array.