OPERATION
Copyright
Trace Engineering Company, Inc.
5916 - 195th Street N. E.
Arlington, WA 98223
Telephone: 360/435-8826
Fax: 360/435-2229
www.traceengineering.com
SW Series Inverter/Charger
Part No. 2031-5
Rev. B: Sept 1, 1999
Page
87
A system that includes 2400 watts of solar array is able to produce approximately 18 amps of AC power at
120 VAC. The output is most needed from 12:00 noon to 18:00 by the utility. If the GRID USAGE TIMER
is set to a START CHARGE TIME of 18:00 and a END CHARGE TIME of 12:00 noon, the inverter will sell
the battery from 12:00 noon to 18:00. The energy in the batteries will be used only if the solar array is not
able to provide enough power to reach the 18 amps AC (determined by the MAX SELL AMPS AC setting
under the BATTERY SELLING MENU (17) menu heading. The battery will assist the solar array to meet
the 18 amps AC MAX SELL AMPS AC setting during the battery sell period. If the battery reaches the
SELL VOLTS DC setting during the sell period, the AC output current will slowly taper down to the solar
array’s output level and the battery will not be further discharged. At 18:00, the battery will charge at the
rate allowed by the SET MAX CHARGE AMPS AC (2 amps AC is the lowest setting allowed). The battery
will be recharged only to the FLOAT VOLTS DC setting unless the BULK CHARGE TRIGGER TIMER
(15) menu heading is used to trigger a bulk charge cycle.
This system offers the utility several advantages. The system can be relied on for a specific amount of
output at a set time. The AC output of the system from 12 noon to 4 PM will not vary with the level of
sunlight (after all, the AC loads on the grid do not suddenly drop when a cloud passes over). Only if it is
extremely cloudy will the system not produce its rated output for the full time period - which would not be
as important since the ambient temperature would not be as high.
This operating mode does not provide an individual system owner with many added values. The wear and
tear on the batteries would be avoided and greater efficiency achieved if the standard sell mode was used.
BATTERY REQUIREMENTS
Batteries are required for utility inter-tie operation of this inverter. The batteries can, however, be small if
the system does not provide back-up power in case of utility failure. Two thousand watt/hours is sufficient
(100 amp/hours at 24 volts is 2400 watt hours). This can be achieved by using two “Group 27” sized
batteries for a 24-volt system. This is a very common size for RV and boat applications. Since the
batteries are not cycled excessively, sealed batteries may be used with good success.
CAUTION: IF USING GELLED BATTERIES, THE BATTERY CHARGER MUST BE SET TO THE
APPROPRIATE SETTINGS OR BATTERY DAMAGE WILL OCCUR.
BATTERY REGULATION LEVEL - SELL MODE
In the SELL mode, the regulation level of the battery is determined by the charge cycle (FLOAT or BULK)
and the settings of the BULK CHARGE TRIGGER TIMER (15) and the GRID USAGE TIMER (18)
settings.
The SET START CHARGE TIME menu item setting under the BULK CHARGE TRIGGER TIMER (15)
menu heading can be used to increase the battery charging regulation voltage to the SET BULK VOLTS
DC setting. The battery voltage will be held near the SET BULK VOLTS DC menu item setting under the
BATTERY CHARGING (10) menu heading for the adjustable ABSORPTION TIME period setting upon
encountering this BULK CHARGE TRIGGER TIMER event or after a loss of AC power to the AC HOT IN
1 input terminal.
The inverter will charge the battery to the FLOAT VOLTS DC setting at the START CHARGE TIME with
the GRID USAGE TIMER enabled (the START CHARGE TIME beginning time is not equal to the END
CHARGE TIME), This is indicated by the FLOAT LED indicator being on. After the END CHARGE TIME,
the inverter turns off the battery charger and begins to “sell” power into the utility grid from the battery (or
any other DC sources available and connected to the batteries) to the SELL VOLTS DC setting. The
FLOAT LED indicator blinking indicates this. The current will be limited to a maximum level controlled by
the MAX SELL AMPS AC menu item setting under the BATTERY SELLING (17) menu heading.
With the GRID USAGE TIMER disabled (the SET START CHARGE TIME beginning time is equal to the
SET END CHARGE TIME) and the inverter in the FLOAT charge cycle, the inverter will use the utility grid
(or any other DC sources available and connected to the batteries) to maintain the batteries to the SET
FLOAT VOLTS DC setting. This is indicated by the FLOAT LED indicator being on.
Summary of Contents for SW II - REV 4.01
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