<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">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 class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><div style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; "><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 type="cite" class="cite" 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 sponsored by Home Power magazine<br><br>List Address: <a href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a><br><br>Options & settings:<br><a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br><br>List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org<br><br>List rules & etiquette:<br>www.re-wrenches.org/etiquette.htm<br><br>Check out participant bios:<br>www.members.re-wrenches.org<br><br></blockquote></div><br></div></div></div></body></html>