Outback Power Systems GS3548E Operators Manual - Manual (Page 37)

Operation
900-0145-01-01 Rev A 35
Offset
This operation is designed to use excess battery energy to power the loads when an AC source is
present. This allows the system to take advantage of renewable energy sources, in effect “offsetting”
dependence on the AC source.
A renewable energy source will raise the battery voltage as it charges the batteries. When the voltage
exceeds a designated reference voltage, the Radian inverter begins drawing power from the batteries
(discharging them) and using that power to offset usage of the AC source. The batteries are kept at
equilibrium and are maintained at the reference voltage.
The Radian inverter uses excess DC energy for offset under the following rules:
 If the load demand is higher than the exported power, the inverter’s use of the AC source is reduced. The
exported amount of 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 exported power) is equal or greater than the load demand, and the Radian 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 Radian inverter uses several set points as reference voltages for the Offset operation, particularly
the 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 Offset 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 Grid Zero mode only uses a single reference voltage for Offset, the DoD Volts setting.
NOTES:
 Offset operation is not available in the Generator, UPS, and Backup input modes.
 Offset operation is available in the Support, Grid Tied, and Grid Zero 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.
 The Grid-Tie Enable menu item must be set to Y (yes) for Offset to work. This is true even if the inverter is
not used in a grid-tied mode or application.
Table 3 Offset Interaction with AC Source
Mode Excess DC ≥ loads Excess DC < loads
Generator N/A; Offset operation does not function
Support Offsets load use, but also uses DC and batteries to support the AC source based on Support mode settings
Grid Tied Sells excess to AC source (grid); remains connected Offsets load use with whatever power is available
UPS N/A; Offset operation does not function
Backup N/A; Offset operation does not function
Mini Grid Offsets load use with whatever power is available; inapplicable if disconnected from utility grid
Grid Zero Offsets load use, but only according to the DoD Volts setting