net metered system question [RE-wrenches]

[sunwise at cheqnet.net]

David Palumbo, Independent Power & Light wrote:
> 
> What specific equipment are you talking about? And what do you mean by large
> loads on Trace's dedicated loads panel?
> 
In terms of equipment, it takes something on the order of a 25 dollar
contactor/power relay and an enclosure for it along with a small in-line
fuse holder and 5 amp fuse, as well as a little low current, low voltage
cable.  Also, a lovely option, a SPDT toggle switch (no center off) for
overriding the deal.  This, and some of the Trace's cool features allows
you to program the AC1 contactor to open in the evening and close the
following day after the battery has reached bulk voltage (no charge
cycle initiated by the Trace).  AC1 is essentially only available to
inverter when the battery is fully charged and the sun is bright.  

On your other question, when AC1 is lost the inverter drops into search
mode and then powers up anything on the AC OUT of the Trace.  On one
system I've installed this on, her loads are lite (a few efficient
lights and 12cf efficient frig) with the big water pump on it's own
transfer switch dedicated to the grid unless there is a grid failure. 
She runs these loads off the top of her battery each night and yet
another AUX relay in the Trace will re-energize the AC1 contactor if
battery voltage falls too low (through NC contacts and hysteresis
setting).  Actually, the majority of (or all) of the home loads
dedicated to the Trace could be left on a utility energized transfer
relay and dedicated to the utility unless there is a power failure. 
Then inverter loads would be non-existent unless there is a power
failure.  In any case, such a work around will not be very efficient if
the battery is drawn down significantly every night and during cloudy
periods.

To view an archive of the original post (how to) that the pretty smart
Sharkey guy posted, search Topica's Wrench page with "Automatic control
of SW4024" in the search box.

Kurt Nelson

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