<html>
<body>
<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>
<blockquote type=cite class=cite cite>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>
taharvey@heliocentric.org</font></blockquote></body>
</html>