[RE-wrenches] Utility Dis-connect for AC coupled Systems
Drake Chamberlin
drake.chamberlin at redwoodalliance.org
Sat Apr 17 06:59:03 PDT 2010
Hi Jeff,
Use Outback off grid inverters for the backup, and break the AC from
the grid tie inverters. An advantage of this is that you can use a
standard generator and transfer switch to charge batteries through
the off grid inverters. The grid tie inverters take care of the anti
islanding, etc.
Drake
At 10:11 AM 4/16/2010, you wrote:
>Hope I have not posted this before, but it keeps coming up. We do
>many systems that include a battery connected inverter and generator
>to provide backup power for upscale homes. Although we have no
>problem with roof mounted arrays, many of these homes may be large,
>but usually are either shaded or their roofs are broken up with all
>kinds of dormers and chimneys, with no large areas facing south.
>
>In addition, many of these homes have large landscaped yards and
>gardens up against the home, so we end up having to install a
>ground-mounted solar array as much as 200 or more feet away. Since
>we want to charge the battery from the solar array during an outage,
>but do not want to run huge cable sizes due to the long wire runs
>typical for low voltage DC arrays, we mount a SunnyBoy on the back
>of the array, then run 240 VAC back to the
>battery/inverter/generator system in the basement or garage using an
>AC coupled design with relay cut-out to dis-connect on high battery
>voltage during off-grid operation. (still not sure why inverter
>manufacturers can't control over-charging from back-feed AC when not
>grid connected).
>
>Anyway, where to wire in the utility dis-connect that needs to be
>near the meter base. The most logical is in the 240 AC output from
>the solar array inverter before it enters the emergency loads
>panel. However, there is still the matter of the battery inverter
>which could easily backfeed the grid if programming is changed by
>others. This would then require the dis-connect between the AC
>output of the battery inverter and the house panel, but this would
>kill the emergency loads panel if the utility actually decided to
>lock out. Not likely, but still possible. Just concerned that code
>officials will see the inverter in the house, a solar array in the
>yard, and want a dis-connect that kills everything to grid.
>
>Have any other states already addressed this issue?
>
>Jeff Yago
>
>
>
>
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Drake Chamberlin
Athens Electric
OH License 44810
CO License 3773
NABCEP TM Certified PV Installer
Office - 740-448-7328
Mobile - 740-856-9648
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