Gary:
I think you are a little confused about the operating modes of the XW inverter:
In the AC Passthru mode, no battery charging occurs. Below is the passage
from the manual that describes this:
The AC connected to the AC1 or AC2 input is passing directly through the
Xantrex XW
Series Inverter/Charger to the loads. The batteries are not being charged
in this state.
In the normal transfer mode, battery charging does occur. It is my clear
understanding that the Xantrex SW and XW inverters and the Outback FX and
Radian inverters will regulate battery charging so that the charger circuit
uses only excess amperage available. For example: If the input breaker
size is programmed for 60 amps and there is 60 amps of load, 0 amps of AC
will be used for battery charging. If the load decreases to 50 amps, 10
amps of AC will be used for battery charging, etc.. Therefore, the OCPD
does not need to be sized to accommodate both uses of input AC.
Below is a passage from the XW Operating Manual that describes this:
In addition, the battery charger can reduce its charging current to the
batteries
so the combined charge AC current and total load current does not exceed the
capacity of the generator or trip its output breakers or fuses.
Extending this discussion beyond the current topic (pun intended), we need
to understand what happens if the connected loads exceed the input breaker
rating. Here the game changes. The FX inverter can not prevent the
overload from passing to the input breaker, possibly tripping it. The SW,
XW and Radian inverters can provide "Generator Support." Do not confuse
Generator Support with Generator Remote start functions. Generator Support
allows the inverter to sync to, and assist the AC input source in powering
loads. To use the example above: If the load rises to 70 amps, the
inverter draws energy from the batteries to provide the last 10 amps.
Below is the passage from the XW manual that describes this:
AC2 Breaker: Sets the AC2 (Gen) breaker size, based on the size of the
installed AC breaker. The
breaker size must not exceed the capacity of the generator. The Xantrex XW
Series
Inverter/Charger limits the maximum input current to this setting by
derating its charging
current to an equivalent of 80% of the AC breaker size. If the connected
loads exceed the
AC2 breaker setting, the AC breaker trips. The breaker may not trip if Gen
Support is
enabled and Gen Amps is configured not to exceed the generator's rated
output current.
I hope this information is relevant, correct and helpful.
Sincerely,
William Miller
At 08:24 AM 3/1/2013, you wrote:
Larry:
In the case of the Xantrex XW Series, while in the "AC Pass-Thru" Mode,
the internal transfer switch relay connects the protected loads directly
to the AC1 grid input. The XW internal battery charger is then activated
to recharge the battery bank.
The OCPD(s) through which the protected load amps and charging amps are
passing must be sized to accommodate both at the same time.
Regards,
Gary Willett
Icarus Solar
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