What's the cell count on the module that you're planning on using? Most 200W modules I've seen recently use 60 6" cells in series, which is lower than 24V "nominal" (72 cells) and much higher than 12V (36 cells). The attachment didn't come through, but IF the pump uses a permanent magnet DC motor, you should be able to run a 24V motor at 3/4 speed without problem -- if it's something else, I'd talk with Gast about the implications. The LCB, however, might take a little more consideration. I'd talk with the folks at Solar Converters about your plan, and provide them the specs on the module. If their standard unit doesn't have that wide an input voltage range (and I have no idea, honestly), then they might be able to cook you up something specific to your application.<div>
<div><br clear="all">Phil Undercuffler<br><br><br><br><br>
<br><br><div class="gmail_quote">On Tue, May 25, 2010 at 11:18 PM, Howie Michaelson <span dir="ltr"><<a href="mailto:howie@suncatchervt.com">howie@suncatchervt.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Phil,<br>
<br>
Thanks for the info. The pump being considered is a Gast 22D 1180 series,<br>
either the 1002 (12v) or the 1005 (24v) - see attached spec sheet (I think<br>
I can attach now?). I was assuming that using a linear current booster<br>
with a voltage limit such as:<br>
<br>
<a href="http://solarconverters.com/ppt7.htm" target="_blank">http://solarconverters.com/ppt7.htm</a><br>
model PPT 12/24-7V M24<br>
<br>
will protect against over voltage. I was assuming undervoltage wouldn't<br>
hurt the pump much (like using PV direct with an "El Sid" for SHW<br>
pumping), and the LCB will provide the higher current potentially<br>
necessary to start the pump. Am I wrong about these assumptions? I am<br>
leaning toward the 24v pump, since it gives me more overhead with a<br>
smaller LCB.<br>
<br>
Always appreciate the wealth of experience and knowledge this list avails me.<br>
<div class="im"><br>
Howie<br>
--<br>
Howie Michaelson<br>
NABCEP Certified Solar PV Installer<br>
<br>
Sun Catcher, LLC<br>
Renewable Energy Systems Sales and Service<br>
VT Solar & Wind Incentive Program Partner<br>
<a href="http://www.SunCatcherVT.com" target="_blank">http://www.SunCatcherVT.com</a><br>
(cell) 802-272-0004<br>
(home) 802-439-6096<br>
<br>
<br>
</div><div><div></div><div class="h5">On Wed, May 26, 2010 12:51 am, Phil Undercuffler wrote:<br>
> In my experience, there's few problems in the world that can't be solved<br>
> with more PV -- including running pumps with permanent magnet/brush motors<br>
> array direct. However, there's a couple things to be aware of -- first,<br>
> sizing the array. Although the pump may be rated to draw 90 watts when<br>
> running, you need to oversize the array to ensure 90 watts will be<br>
> available<br>
> under normal daily conditions. The exact amount of oversizing depends<br>
> upon<br>
> many factors, but without further testing I'd ballpark an additional 30%<br>
> over rated running watts. Also, the array needs to be larger if the pump<br>
> starts under load, which is highly likely with an aerator (probably<br>
> doesn't<br>
> have an unloader valve, if those work with aerators at all). So far,<br>
> everything leads one to say, rock on with the 180-200 watt modules.<br>
><br>
> But, it's sometimes not so easy. Most 190-200 Watt modules available<br>
> today<br>
> have 60 cells, and don't nicely align with 12 or 24V "nominal" voltages.<br>
> Does your aerator come in two flavors, 12V or 24V, please specify your<br>
> preferred voltage upon order? Or does it have electronics built in, and<br>
> will take anything in a range between 12V and 24V (unlikely, but<br>
> possible)?<br>
> If the former, then you really need to find some module combination that<br>
> provides 36 or 72 cells in series -- otherwise, you'll either run the pump<br>
> under or overspeed, which will impact longevity and performance. If the<br>
> latter, make sure it will be happy with the voltage the module puts out --<br>
> over the full range of conditions.<br>
><br>
> Empirical testing can sometimes be the best approach with a project like<br>
> this, but it's a good idea to do a little homework beforehand, to best<br>
> know<br>
> what the expected behavior should be. Good luck with it, it sounds like a<br>
> fun project!<br>
><br>
> Phil Undercuffler<br>
><br>
><br>
><br>
><br>
><br>
><br>
> On Tue, May 25, 2010 at 9:30 PM, Howie Michaelson<br>
> <<a href="mailto:howie@suncatchervt.com">howie@suncatchervt.com</a>>wrote:<br>
><br>
>> Hi all,<br>
>><br>
>> I have a project to provide PV power for a small diaphragm air pump (1/8<br>
>> hp, 12 or 24 vDC, 6.2 or 3.5 running amps, 90 watts). As it turns out,<br>
>> pricing from my distributor is cheaper for 180-200 watt modules than for<br>
>> anything smaller. I don't spec PV driven pumps except for SHW, so I'm<br>
>> just checking for any reason to not use the larger modules. The pump is<br>
>> being used to aerate a pond, so no problem with excess pumping. I will<br>
>> most likely use a linear current booster to improve output, but mostly<br>
>> to<br>
>> limit voltage. Any advice would be welcomed.<br>
>><br>
>> Thanks,<br>
>> Howie<br>
>> --<br>
>> Howie Michaelson<br>
>> NABCEP Certified Solar PV Installer<br>
>><br>
>> Sun Catcher, LLC<br>
>> Renewable Energy Systems Sales and Service<br>
>> VT Solar & Wind Incentive Program Partner<br>
>> <a href="http://www.SunCatcherVT.com" target="_blank">http://www.SunCatcherVT.com</a><br>
>> (cell) 802-272-0004<br>
>> (home) 802-439-6096<br>
>><br>
>><br>
>><br>
>><br>
>><br>
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