Offset; Table 4 Offset Interaction With Ac Source - Outback Power Systems FXR2012E Operator's Manual

Operation

Offset

Offset is an automatic operation which occurs in certain conditions. It is not a programmable function.
This operation uses excess battery energy to power the loads when an AC source is present. The
system can take advantage of renewable energy sources, "offsetting" dependence on the AC source.
The battery voltage increases as a renewable energy source charges the batteries. When the voltage
exceeds a designated reference voltage, the FXR inverter begins inverting. It draws power from the
batteries (discharging them) and uses that power to offset the use of the AC source.
The FXR inverter uses excess DC energy for offset under the following rules:

If the load demand is higher than the inverted power, the inverter's use of the AC source is reduced. The
amount of inverted power has "offset" the same amount of demand on the AC source. (This is sometimes
known as "selling to the loads".)

If the excess DC energy (and inverted power) is equal or greater than the load demand, and the inverter is in
the Grid Tied input mode, the inverter will sell the additional power to the utility grid. This is the key priority
of the Grid Tied mode.
The FXR inverter uses several set points as reference voltages for the Offset operation, particularly the
FXR battery charger settings.

The charger settings Absorb Voltage, Float Voltage, and Equalize Voltage (as shown in the system display)
are all used as reference voltages. Normally the charger regulates to these set points by adding power to
the batteries. Offsetting does the opposite; it uses the same set points but regulates the voltage by
removing power from the batteries.

If none of the battery charger's timers are active, the reference voltage is Sell Voltage in the Grid-Tie Sell
menu. This is true in any input mode where Offset is used, not just the Grid Tied input mode.

The GridZero mode only uses a single reference voltage for Offset, the DoD Volts setting.
NOTES :

The Offset Enable menu item must be set to Y (yes) for Offset to work.

Offset operation is available in the Support, Grid Tied, and GridZero modes.

Offset operation is available in the Mini Grid mode. However, it may not be used often since the Mini Grid
priority is to avoid grid use.

Offset operation is not available in the Generator, UPS, and Backup input modes.
Mode
Generator Does not function
Offsets load use, but also uses DC to support the AC source based on Support mode settings
Support
Grid Tied Sells excess to AC source (grid); remains connected
Does not function
UPS
Backup Does not function
Offsets loads with whatever power is available; inapplicable if disconnected from utility grid
Mini Grid
GridZero Offsets load use, but only according to the DoD Volts setting
42
Table 4 Offset Interaction with AC Source
Excess DC ≥ loads Excess DC < loads
Offsets loads with whatever power is available
900-0169-01-00 Rev A