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<DIV><FONT size=2 face=Arial>Troy,</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Unless you are going to be your client's power
plant manager, he or she is going to have to be responsible for at least system
operation which means managing production and consumption - or hire someone to
manage the system. PV systems are automatic and virtually maintenance-free to
some extent. A well-designed, properly installed batteryless grid-tie
residential PV system's operation is transparent to the home occupants and
requires very little attention. However, a battery-based system regularly
requires operator intervention especially in a region with frequent brown-outs
and black-outs. </FONT><FONT size=2 face=Arial>There are several Wrenches who
live with battery-based grid-tied PV systems. Do any of you power your whole
house through the main service panel (no subpanel)? If yes, what size PV array,
inverter, and battery bank? Any battery-based, grid-tied PV systems out there in
continuous operation since before June 1998?</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Joel Davidson</FONT></DIV>
<BLOCKQUOTE
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=walters@taosnet.com href="mailto:walters@taosnet.com">R. Walters</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=re-wrenches@lists.re-wrenches.org
href="mailto:re-wrenches@lists.re-wrenches.org">RE-wrenches</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, June 23, 2009 10:29
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [RE-wrenches] Grid-Connect
Inverter with battery,AND auto backoff?</DIV>
<DIV><BR></DIV>We've looked at a variety of approaches over the years. My
current thinking, is that you want some non critical loads to shut off during
an outage, so the customer knows they are on backup power. With whole house
backup, they never know till the batteries are gone too. I've found that with
creative picking of circuits, the customer can be signaled that the grid is
out, without creating any panic or hardship. Most houses have so many circuits
that its just not a big deal to have the washing machine not work for a few
hours.
<DIV>I'd back off to a proven design, otherwise your going to spend a lot of
time with them making this work. Manually switchable double throw breakers are
available and work well, but yes, you do have to exert some slight mental and
physical effort to operate them. Automatic anything means the installer is
always to blame. Good system design puts some responsibility on the operator
as well.</DIV>
<DIV><BR>
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<DIV>R. Walters</DIV>
<DIV>Solarray.com<SPAN style="WHITE-SPACE: pre"
class=Apple-tab-span></SPAN></DIV>
<DIV>NABCEP # 04170442<SPAN style="WHITE-SPACE: pre"
class=Apple-tab-span><SPAN style="WHITE-SPACE: pre" class=Apple-style-span>
</SPAN></SPAN></DIV>
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<DIV>
<DIV>On Jun 23, 2009, at 10:30 PM, Troy Harvey wrote:</DIV><BR
class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">Load sheding is not a bad idea if the tech exists.
Not particularly complex either with networkable breakers and a smart
controller in the inverter. Just software. Cost isn't an issue, they are
willing to pay.
<DIV><BR></DIV>
<DIV>The issue on loads isn't battery cut-off (though that isn't a bad
idea), but shedding the less-important loads to make sure the house does
exceed the inverter power output. A 6kW inverter subpaneled will only give
you about four 15 AMP circuits. However a typical house of this size will
have 30 such circuits, yet good chance it won't be drawing much more than 50
AMPs for the whole house at any one time. How do you select what is
important? Either the inverter is complicated or
the electricians wiring is complicated.</DIV>
<DIV>
<DIV><BR>
<DIV><BR>
<DIV apple-content-edited="true"><SPAN
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<DIV
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<DIV>Troy Harvey</DIV>
<DIV>---------------------</DIV>
<DIV>Heliocentric</DIV>
<DIV>801-453-9434</DIV>
<DIV><A
href="mailto:taharvey@heliocentric.org">taharvey@heliocentric.org</A></DIV></DIV><BR
class=Apple-interchange-newline></SPAN></DIV><BR>
<DIV>
<DIV>On Jun 23, 2009, at 10:01 PM, William Miller wrote:</DIV><BR
class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">
<DIV><FONT size=3>Troy:<BR><BR>Let me guess... They want it right away and
cheap, too. Generally speaking, this is an impractical
request. Electrically operated circuit breakers or 20 A relays and
controllers are expensive and complicated. One thing to learn in
this trade is when to try and talk a client out of a bad idea, and when a
client has such wacky ideas that it is best to walk away.<BR><BR>I could,
however, suggest two ways to do this:<BR><BR>1. Use two inverters and set
the LBCO for one high. Connect one to critical loads and one (with
the high LBCO) to non-critical loads. When the batteries start
getting low, the non-critical-loads inverter shuts down, leaving the
critical-loads inverter running.<BR><BR>Realize that you now need four
load centers: Grid, generator (you have recommended a generator so
they can use their wide screen TV during a wind storm, correct?),
non-critical loads and critical loads. This type of design gets
complicated fast. Will the AHJ be able to track this? Set a
clause that allows you to collect hourly fees when they require three
different meetings and three re-writes of the permit
application.<BR><BR>2. Use an Outback with external relays to shut off
loads when the battery voltage falls below a certain point.
This is a crude approach, the parameters are not flexible (hard coded
delay values) and it requires custom built relay panels, time consuming,
expensive and a potential service problem.<BR><BR>Either system is
actuated on battery voltage rather than loads. Inverters I am
familiar with have relays and internal controls that operate based a
set-able battery voltages, but I know of none that has a programmable
relay to actuate at a certain load level. In addition, loads change
so rapidly that this type of switching would be erratic. Loading is
a component of battery voltage, anyway, so you are including that
indirectly.<BR><BR>Good Luck,<BR><BR>William Miller<BR><BR><BR><BR>At
07:41 PM 6/23/2009, you wrote:<BR></FONT>
<BLOCKQUOTE class=cite cite="" type="cite"><FONT size=3>Hi
folks,<BR><BR>I need an inverter/charger/controller solution for a grid
connect <BR>house that:<BR>1. grid-connects (net-meters)<BR>2.
Islands off of the battery in outages (whole house UPS)<BR>3. Feeds into
the whole house breaker, so the whole house is backed up<BR>4. Shuts
down less important breakers as needed, if the load for the
<BR>whole house is over the inverter limit<BR><BR>Instead of guessing
which breakers are important to put on a battery <BR>backed up
sub-panel, my client would like the whole house backed up. <BR>But
of course, can't guarantee that the house won't be drawing too
<BR>much for a 6000 Watt inverter at any given time. So would like to
have <BR>the system intelligently remove less important breakers
until the <BR>system is below the inverter operation
wattage.<BR><BR>Anyone know of a inverter system that is smart like
that?<BR><BR>Troy
Harvey<BR>---------------------<BR>Heliocentric<BR>801-453-9434<BR><A
href="mailto:taharvey@heliocentric.org">taharvey@heliocentric.org</A></FONT></BLOCKQUOTE></DIV>_______________________________________________<BR>List
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