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Nathan,<br>
I neither stated nor implied that the SW series could be AC-coupled,
because I don't know, friend. I have never had reason to try this.
The issue was discussed on this forum several years ago, and I have
found two key posts from David Katz of AEE about this topic in my
email Wrenches archives. David only addresses compatibility with
early Sunny Boys. The SW is true modified sine waveform, so whether
is would be capable of providing a reference signal to which a
modern grid-tie inverter could latch would be subject to several
variables, and would likely vary among inverter brands and models.
Here's what David wrote on 4/15/2005, excerpted:<br>
<blockquote>I have connected Sunny Boy inverters directly to the
output of Xantrex SW inverters and Outback inverters. It works
well. The Sunny Boy operates when it sees the SW or Outback
output. Sometimes it shuts off when a large load, like a pump is
applied to the circuit, because it looks like a grid failure. If
the SB shuts off, it waits 5 minutes to turn on. If there is no
AC load on the system and the SB is supplying power, you will
charge the batteries connected to the SW. You need to put a
voltage controlled switch to turn of the AC between the Sunny Boy
and the sub panel if the battery voltage gets too high.<br>
<br>
The SW is bi-directional. if you put ac into the output, it
charges the battery. The AC in terminal is connected directly to
the output through a relay. The inverter is quite amazing. If you
connect the output of the SB and the SW to the same sub panel and
turn off all loads you will see it charge the battery. If you turn
on loads to the point you are drawing more than the SB is
supplying, it will begin to draw power from the battery and supply
the excess that the SB is not supplying. I use an outback for
backup power on my grid connected house this way. As long as the
SW in turned on, there is a sine wave present at the AC output.
This makes the SB think the grid is present. I hope this answers
your question. If not let me know and I will try to draw a
diagram.
<br>
By the way, if you connect the AC input of the SW or (FX) to a
breaker in the main panel in a grid connected system it will
become your connection from the main panel to the sub panel
(120VAC) and the inverter will turn on whenever the grid fails and
keep the SB running. If you are using a 240 V SB, you will need an
autotransformer or a second SW.
<br>
David
<br>
</blockquote>
You mention the GTI below, but have not indicated whether the SW you
are considering is or isn't a GTI-equipped model. If it is
4.10/GTI-equipped, I'd suspect it's incompatible with AC-coupling.
When one of these is not selling (such as at night), has no loads on
it but is grid-connected, it is continually drifting between buy and
sell by an amp or two. Note that I have only observed this on the
SW's meter display, which is a pretty crude measurement. But I would
expect that this would interfere with any GT inverter's latching
function, given the mandatory 5-minute waiting period.<br>
<br>
This is all based on observing one system that we installed around
2002 for a well-known retired movie star. The system remains fully
operational today. We had an SW5548 (for most loads) and an SW 4048
(for background loads with surge, like pumps) that were not
series-stacked, in a GTWB system, small by today's standards at
4.4kW of PV. Both inverters had GTIs, but only one was set to sell,
in order for the two SWs not to argue with each other and to
minimize their inherent float inefficiency previously noted. <br>
<br>
I'd guess your chances of AC-coupling would be better with a pre-GTI
unit. Others here may have had more experience with this question. <br>
<br>
Just to stir the pot some more, here is an email from Lloyd Gomm,
then at Xantrex, about the GTI/listing issue from 11/17/2003:<br>
<blockquote>Joel Davidson Wrote:
<blockquote type="cite" style="color: rgb(0, 0, 0);">November 15,
2003 one of our customers (maybe more) with a line-tie SW in
Southern California Edison territory got a notice from Xantrex
dated October 22, 2003 about a required firmware update. Anyone
else get this notice? </blockquote>
Joel, this firmware update is necessary for SW inverters tested /
listed by UL. This batch of SW's were produced by Xantrex between
Q4 2000 and Q4 2001 and, to be clear, were de-listed by UL in
November 2001.
<br>
<br>
This firmware update is NOT required for ETL or CSA marked SW's
tested to UL 1741 under the NRTL program. Everything produced
after Q4 2001 are CSA marked, GTI compatible SW's. Everything
produced before Q4 2000 was listed by ETL and is unaffected. <br>
We have been working with SCE, SDG&E, and PG&E to minimize
impact on home owners and dealers. The firmware update is easy to
accomplish and we are compensating dealers to do the work ( 2hrs
per SW @ $65 per hour plus a $50 per site allowance). The
compensation is paid by check within 2 weeks of receipt of our
form. We have contacted all dealers who have customers with an
inverter that requires the update.
<br>
<br>
Joel Davidson Wrote:
<blockquote type="cite" style="color: rgb(0, 0, 0);">This
particular customer is a retired aerospace engineer whose SW4048
was working fine, but still had to get a GTI and now has to get
some firmware. </blockquote>
Joel, if this customer has a GTI he does not require the firmware
update. Please contact me so we can update his information. This
will allow us to close the loop with his utility.
<br>
<br>
If anyone requires any further information on this program please
contact me off list. <br>
Lloyd Gomm
<br>
Director, Marketing
</blockquote>
Allan<br>
<br>
<div class="moz-signature">
<meta http-equiv="content-type" content="text/html;
charset=ISO-8859-1">
<title></title>
<font face="Times New Roman, Times, serif"><b>Allan Sindelar</b></font><br>
<small><a href="mailto:Allan@positiveenergysolar.com"><font
color="#000099" face="Times New Roman, Times, serif"><u>Allan@positiveenergysolar.com</u></font></a></small><font
face="Times New Roman, Times, serif"><br>
<span style="font-size: 10pt;">NABCEP Certified Photovoltaic
Installer<br>
NABCEP Certified Technical Sales Professional<br>
New Mexico EE98J Journeyman Electrician<br>
<b>Positive Energy, Inc.</b><br>
3201 Calle Marie<br>
Santa Fe, New Mexico 87507<br>
<b>505 424-1112</b><br>
<a href="http://www.positiveenergysolar.com/" target="_blank"><u>www.positiveenergysolar.com</u></a><o:p></o:p></span></font>
<span style="font-size: 10pt;"><br>
</span> </div>
<br>
On 11/22/2011 8:10 AM, Nathan Jones wrote:
<blockquote
cite="mid:1321974619.14258.yint-ygo-j2me@web113604.mail.gq1.yahoo.com"
type="cite">
<pre wrap="">Bill,
I believe Allans post indirectly answered my question. While he did not specifically state the SW could be used in an AC coupled arrangement, I believe it was implied. Since the listing issue, as I understand it, was due to failure to drop out of sell mode in a certain set of circumstances and never had anything to do with the behavior of the inverter in any of its "incoming AC only" settings as far as disconnecting there should not be any question as to its suitability for AC coupling there. The only question would be how they would react and manage backfed AC from a GTI in event of a grid failure. That question is unknown to me and has not been specifically answered yet. Any one have an answer to that?
Nathan Jones
Power Source Solar
Springfield, Mo
R
417-827-0738</pre>
</blockquote>
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