Hey Kelly,<br><br>I think that's probably the best solution. I don't think it should be necessary with Sunny Boys in gridtied system, but it's certainly the safest bet. I'm not sure if all SB's come with the right firmware, or if it's a special option, but they can be programmed to allow for a wide grid frequency window. This is used in the AC coupled arrangement with the Sunny Island. When the Sunny Island's batteries are full it starts to raise the grid frequency slightly. The SB's read this as an instruction to reduce their output and pull their arrays off MPP. At a defined frequency, the SB's shut down entirely.<br>
<br>So, the stories of SB's frying generators in off grid, AC coupled systems makes me think that the tight frequency window required for grid-tied systems had been replaced by the wider window used for communication with the Sunny Island. It was one of the first prototypes of these systems so it might be a little different now, but I installed a system that allowed the SI supported grid to range from 50Hz all the way up to 54Hz before the SB's shut down. That could allow quite a bit of backfeeding of the generator and might explain the generators being fried in these SI/SB AC coupled systems. I would think that with regular gridtied SB's they'd shut down before damaging the generator.<br>
<br>Bottom line, though, I'd probably install the NC relay powered off the generator input to be safe.<br><br>Dana<br clear="all"><br>-- <br>Dana Brandt<br>Ecotech Energy Systems, LLC<br><a href="http://www.ecotechenergy.com">www.ecotechenergy.com</a><br>
<a href="mailto:dana@ecotechenergy.com">dana@ecotechenergy.com</a><br>360.510.0433<br><br><br><div class="gmail_quote">On Thu, Nov 20, 2008 at 9:57 AM, Kelly Keilwitz, Whidbey Sun & Wind <span dir="ltr"><<a href="mailto:kelly@whidbeysunwind.com">kelly@whidbeysunwind.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">All,<br>
I suppose a normally-closed relay on the inverter output, with coil<br>
energized from the generator (i.e. It opens when the genny is on) might be<br>
easier than a NO relay on the grid-side. Anyone do it this way?<br>
<font color="#888888"><br>
-Kelly<br>
</font><div class="Ih2E3d"><br>
<br>
On 11/20/08 9:30 AM, "Kelly Keilwitz" <<a href="mailto:kelly@whidbeysunwind.com">kelly@whidbeysunwind.com</a>> wrote:<br>
<br>
><br>
> The relay seems like a reasonable solution. However, if the main panel is<br>
> entirely backed up by the genny, to power the relay from the grid (only)<br>
> requires a line-side tap, yes? Is there a simple solution that Im missing?<br>
><br>
<br>
<br>
<br>
<br>
<br>
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