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text="#000000" bgcolor="#FFFFFF"><div style="font-family:
Helvetica,Arial,sans-serif;"><span style="font-family:
Helvetica,Arial,sans-serif;">Hi Drake,<br><br>A GENTRAN or equivalent is
standard equipment for adding a backup generator to a house or small
business as an alternative to one main manual or automatic transfer
switch. It's simply a box with 8-12 individual transfer switch
breakers some 120 and a few 240 - mostly 15 and 20 amp. They sell
plug-in types and hard wire types where the output of a small gas
generator is either plugged into the face of the unit or hardwired into
the buss. <br><br>Then there is a bundle of wires that run from the
GENTRAN to the house breaker panel. For each house circuit you want to
backup you simply interupt the load line coming out of that main panel
circuit breaker with the 2 lines from the individual transfer switches
in the GENTRAN. So on the GENTRAN you switch each circuit between "GEN"
or "Utility". Then you simply use the output of your new off-grid
solar inverter to feed the GEN side and during a power outage you can
not only switch your house over to your solar inverter with no dedicated
critical loads subpanel but you can control how much load you want to
put on your backup solar.<br><br>I've used 2 GENTRANS to cover all the
circuits in a house - so IMHO it's better than a dedicated subpanel or
an all-house automatic transfer switch in that you can pick and choose
how much load you want to expose your inverter and batteries too. The
only disadvantage is they only usually come in 15 and 20 amp circuits
and usually offer only one or 2 240 Volt circuits. If you want to
empower a 30 or 50 Amp 240 circuit - there are other companies that sell
GENTRAN type switches with customizable breaker options but they are
much more expensive.<br><br>Do watch your neutral and grounding circuits
though. Since the neutral is bonded at the Main panel you want to be
consistent with the "grounded conductor grounded at one and only one
point rule" when the GENTRAN is installed and switched - a point many
electricians miss when they install backup generators.<br><br>Hope that
helps.<br><br>Jeff Clearwater<br>Village Power Design<br>NABCEP™
Certified PV Installer<br>C-46 CA Solar Contractor<br><br></span><br>Drake
wrote:<blockquote
cite="mid:20111110125716.0CC5228406B@homiemail-a47.g.dreamhost.com%3E%20(sfid-20111110_07571_50C64F13)"
type="cite">
The GENTRAN sounds very interesting. The Internet has some for
sale, but so far no detail. Will the 12 circuit panel shed
one circuit at a time? In a nutshell, how does this
work?<br><br>
<br>
Thanks,<br><br>
Drake <br><br>
<br><br>
At 02:32 AM 11/10/2011, you wrote:<br>
<blockquote type="cite" class="cite" cite="">Hi Wrenchies,<br>
<br>
Yes and if you use a GENTRAN or equivalent circuit-by-circuit transfer
switch add-on for the output from the offgrid inverter to your AC panel
- then there is no need for a separate dedicated AC loads panel and
rewire like in Larry's original drawing. I've used this trick for
years to avoid a dedicated subpanel for the output of an off-grid
inverter. Combined with the DC transfer switch idea that high
voltage MPPTs enable, (we've been waiting for this) you have a
really simple retrofit for an on-grid system. <br><br>
And now with Magnum and others offering low-power 120/240 split phase
outputs in one inverter - the grid-tie hybrid retrofit market is getting
more attractive all the time. DC Transfer Switch to MPPT Charger to
120/240 split phase inverter/battery to GENTRAN Switch. Getting
cheaper all the time.<br><br>
And hopefully one day not too far off SMA will bring their "Backup
Set S" they show in their European catalog to the States- this is
basically a 2.2 KW version of the Sunny Island - 2 of them would achieve
120/240 stacked and be a nice cheaper SB enabler as well.<br><br>
Also your standard 100 AMP 4 pole DPDT transfer switch may not be rated
for 600 VDC explicitly but think of it - the old knife style units
"throw" is like 12" - no way that won't work with 600
VDC.<br><br>
Hope that helps!,<br><br>
Jeff<br><br>
<br><br>
<br><br>
Larry Crutcher, Starlight Solar Power Systems wrote:<br>
<blockquote type="cite" class="cite" cite=""><br>
<pre>Right.... a major rewire and many components...and sacrifices. The
Outback is limited to 30 amps AC and cost much more than you would need
to spend.
With my idea you just add a transfer switch....Done. When the grid is
down, PV feeds HV CC. Then you can use ANY size inverter, with or without
a transfer switch. No rewiring the grid inverter. No 240 volt
transformers or dual inverters. No relays, switches or diversion
controllers. Batteries are always properly maintained. No phantom loads.
Very simple.
Thanks for your input. Now if I can just find that darn 600 volt transfer
switch.
Larry Crutcher
Starlight Solar Power Systems
On Nov 9, 2011, at 1:55 PM, Drake wrote:
</pre>
<blockquote type="cite" class="cite" cite=""><br>
<pre>Any amount of power will AC couple.
If you use an off grid inverter, such as an Outback, to feed the
protected load panel, the inverter should be fed by grid AC power to
supply loads, when the grid is available. Just feed your grid
tie inverter into the protected loads panel. You will need a
relay to shut off power from the grid tie inverter when the batteries are
full. This can be triggered by the fan relay in the Outback.
The on grid inverter will push power into the grid through the battery
inverter's internal transfer switch during normal operation and AC couple
when the power is out. If your grid tie inverter is 240 volts, you
will need to use a transformer or two inverters.
The phantom load of the inverter can be eliminated by using a transfer
switch to send PV power straight to the grid, during normal grid
availability, keeping the inverter turned off. AC coupling seems
much easier than using a charge controller, but there is no conditioning
of the batteries. The charge is just on and off at the voltage set
point. For a back up system, that is not much of a problem, as the
battery inverter can maintain the batteries when power is available.
At 02:04 PM 11/9/2011, you wrote:
</pre>
<blockquote type="cite" class="cite" cite=""><br>
<pre>Nice Find, Drake! Thanks.
What is the minimum system for an AC coupled inverter?
Again, the idea is for low cost battery backup of an existing grid tie.
The AC coupled schematics I have looked at require a major rewire and
many components. I would like to hear if someone has a simple add on
solution compared to just switching the array to the high voltage CC.
Larry Crutcher
Starlight Solar Power Systems
</pre></blockquote></blockquote>
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<x-sigsep><p>
<font size="2">Drake
Chamberlin<x-tab> </x-tab>
<br>
ATHENS ELECTRIC LLC<br>
OH License
44810<x-tab> </x-tab><br>
CO license 3773<br>
NABCEP Certified PV<br>
</font>
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