<div dir="auto">Hi Scott, </div><div dir="auto"><br></div><div dir="auto">About a year ago I backed up two separate 200A panels on a 320A service with two separate Sol-Ark 15K units and two separate battery banks. Although the separate systems functioned just fine, I was getting really crazy power flow data in the app. Sol-Ark tech support suggested that I combine the two systems (combine the battery bank and AC input/output). Apparently, upstream PV production can adversely affect the downstream system’s monitoring. Luckily, the electrical layout of the existing infrastructure allowed for me to combine the two systems fairly easily. After I combined everything, the monitoring issues cleared up. The PV in this case was DC connected and evenly split between the two inverters. But I could definitely see an AC connected PV system causing headaches with the other system when it goes to frequency shift it’s connected PV production. </div><div dir="auto"><br></div><div dir="auto">The other thing to keep in mind with separate systems is that if a generator is connected, controlling it from both inverters is clunky and using only one system to control the generator leaves the possibility that the other might turn off from low SOC before the generator turns on. But it sounds like you are talking about a grid tied system with AC PV input, so I’m thinking a generator probably isn’t at play. </div><div dir="auto"><br></div><div dir="auto">I’d be curious to hear what Sol-Ark tech support has to say about your configuration and if they would also suggest combining them. </div><div dir="auto"><br></div><div dir="auto">Best,</div><div dir="auto"><br></div><div dir="auto">Chris </div><div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Wed, Oct 22, 2025 at 1:52 PM scot.arey--- via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">
<div style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
Background: New customer wants both 200-amp panels backed up and neither can be "slimmed down" to allow just one backup panel so looking at dual, but not paralleled, SA15 (or 18).<br>
<br>
The design / cost-reduction opportunity: There is one 100-amp set of inground conductors already going out to where ground mount would be. My immediate thought is to use this wire already in ground to transport output of solar ground mount. I'd put a large
grid-tied inverter at the ground mount and "de-aggregate" the AC via a load center by the Sol-Arks, and AC couple half to each Sol-Ark. No trenching...both Sol-Arks have AC-coupled input</div>
<div style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
The question I need help/ideas on: What happens to frequency shift if just one Sol-Ark /battery combo is near-full SoC during backup ops and shifts to 62hz to shutdown the AC-coupled GTI. Seems it would shift the ac-couple POI to 62hz but the other inverter
would still be at 60hz still and this conflict might not "mix well" getting back to the grid-tied inverter at the ground mount.</div>
<div style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
I may well come back to the option of new trenching and pulling separate DC conductors to each Sol-Ark and get the simplest, least complex design but I'm exploring all design options to use existing wire and not have to trench.<br>
<br>
Best analogy I can come up with, is that like an Outback system having "float charging coordination," I could have "freq shift coordination" between the Sol-Arks and of course that is not a feature in non-paralleled inverters.<br>
<br>
I suppose combining the separate 200-amp services and then paralleling the Sol-Ark inverters to this might be the necessary actions if I want to avoid trenching and still back up all.</div>
<div id="m_2755130789067718604Signature">
<div style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
<br>
</div>
<div style="direction:ltr;text-align:left;text-indent:0px;background-color:rgb(255,255,255);margin:0px;font-family:"Segoe UI","Segoe UI Web (West European)",-apple-system,BlinkMacSystemFont,Roboto,"Helvetica Neue",sans-serif;font-size:15px;color:rgb(36,36,36)">
<b>Howard "Scot" Arey</b></div>
<div style="direction:ltr;text-align:left;text-indent:0px;background-color:rgb(255,255,255);margin:0px;font-family:"Segoe UI","Segoe UI Web (West European)",-apple-system,BlinkMacSystemFont,Roboto,"Helvetica Neue",sans-serif;font-size:15px;color:rgb(36,36,36)">
<b>Owner, Solar CenTex</b></div>
<div style="direction:ltr;text-align:left;text-indent:0px;background-color:rgb(255,255,255);margin:0px;font-family:"Segoe UI","Segoe UI Web (West European)",-apple-system,BlinkMacSystemFont,Roboto,"Helvetica Neue",sans-serif;font-size:15px;color:rgb(36,36,36)">
<br>
</div>
<div style="direction:ltr;text-align:left;text-indent:0px;background-color:rgb(255,255,255);margin:0px;font-family:"Segoe UI","Segoe UI Web (West European)",-apple-system,BlinkMacSystemFont,Roboto,"Helvetica Neue",sans-serif;font-size:15px;color:rgb(36,36,36)">
NABCEP PV Installation Professional</div>
<div style="direction:ltr;text-align:left;text-indent:0px;background-color:rgb(255,255,255);margin:0px;font-family:"Segoe UI","Segoe UI Web (West European)",-apple-system,BlinkMacSystemFont,Roboto,"Helvetica Neue",sans-serif;font-size:15px;color:rgb(36,36,36)">
TECL 29755</div>
<div style="direction:ltr;text-align:left;text-indent:0px;background-color:rgb(255,255,255);margin:0px;font-family:"Segoe UI","Segoe UI Web (West European)",-apple-system,BlinkMacSystemFont,Roboto,"Helvetica Neue",sans-serif;font-size:15px;color:rgb(36,36,36)">
254-300-1228 </div>
<div style="text-align:left;text-indent:0px;background-color:rgb(255,255,255);margin:0px;font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
<img src="cid:ii_19a0d34c7974bb066c91" style="width:852px;max-width:100%"></div>
<div style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
<br>
</div>
</div>
</div>
_______________________________________________<br>
List sponsored by Redwood Alliance<br>
<br>
Pay optional member dues here: <a href="http://re-wrenches.org" rel="noreferrer" target="_blank">http://re-wrenches.org</a><br>
<br>
List Address: <a href="mailto:RE-wrenches@lists.re-wrenches.org" target="_blank">RE-wrenches@lists.re-wrenches.org</a><br>
<br>
Change listserver email address & settings:<br>
<a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org" rel="noreferrer" target="_blank">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br>
<br>
There are two list archives for searching. When one doesn't work, try the other:<br>
<a href="https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/" rel="noreferrer" target="_blank">https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/</a><br>
<a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org" rel="noreferrer" target="_blank">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><br>
<br>
List rules & etiquette:<br>
<a href="http://www.re-wrenches.org/etiquette.htm" rel="noreferrer" target="_blank">http://www.re-wrenches.org/etiquette.htm</a><br>
<br>
Check out or update participant bios:<br>
<a href="http://www.members.re-wrenches.org" rel="noreferrer" target="_blank">http://www.members.re-wrenches.org</a><br>
<br>
</blockquote></div></div>