Troy:
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.
I could, however, suggest two ways to do this:
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.
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.
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.
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.
Good Luck,
William Miller
At 07:41 PM 6/23/2009, you wrote:
Hi folks,
I need an inverter/charger/controller solution for a grid connect
house that:
1. grid-connects (net-meters)
2. Islands off of the battery in outages (whole house UPS)
3. Feeds into the whole house breaker, so the whole house is backed up
4. Shuts down less important breakers as needed, if the load for the
whole house is over the inverter limit
Instead of guessing which breakers are important to put on a battery
backed up sub-panel, my client would like the whole house backed up.
But of course, can't guarantee that the house won't be drawing too
much for a 6000 Watt inverter at any given time. So would like to have
the system intelligently remove less important breakers until the
system is below the inverter operation wattage.
Anyone know of a inverter system that is smart like that?
Troy Harvey
---------------------
Heliocentric
801-453-9434
tahar...@heliocentric.org
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
