Hi Allan,<br><br> Oversizing the unit seems to help a bit with durability in that when operating it's at less than full output (the con is usually increase fuel consumption). I'm guessing that at 7800' you have about 20% derate anyway, and I believe its a bit harder to find less than 20K. If those other units were running often at full tilt, it might be the answer to their premature failure. Make sure your gas is plumbed well and the pressure is checked to spec of the unit. Find a knowledgeable salesperson and be sure they understand the off grid application. Ask specifically about the cold weather/ altitude features you are looking for, and be certain that they aren't reliant on something like the transfer switch (a problem we just ran into this fall) or some other part we don't use for off grid.<br>
<br> It seems as though we always have to be a bit creative dealing with the phantom loads of either a battery charger, or carb/throat, heaters, etc. We have never opted for the battery heaters as we just pick an over sized gel starting battery and make certain we have a good trickle charge mechanism to keep it topped off. It seems to be quite effective. We have found that either using a separate trickle charge unit on its own system (a module on a small pole next to the unit), or just using a regular AC trickle charger on a timer seems to work well with the charger only energized during a few full sun hours 12:00-2:00 or so . The Throat heaters are a bit more tricky. It seems like some gen units need them more than others. I have clients that never need any kind of heat unit, and others that seem to have to have the boost. A good solution if you need it is the Atkinson gen start module with the pre heat option. It only energizes for a short time as if it were a glo plug after the relay is tripped by the gen start. I think the Xantrex XW AGS unit has the preheat relay already on board.<br>
<br>Other heads up is snow. Even with its own enclosure, if the client isn't there to maintain intake and exhaust clearance it can potentially choke out with snow around the unit. Simply raising the pad can help, maybe have a overhang roof for snowshed. It also makes it easy for oil changes/ maintenance. <br>
<br>Jay<br><br><br><br>Jay Pozner<br>Nunatak Alternative Energy Solutions<br>PO Box 2948<br>Crested Butte, CO 81224<br>(970) 349-3432<br>
<br><div class="gmail_quote">On Mon, Jan 9, 2012 at 8:59 PM, Allan Sindelar <span dir="ltr"><<a href="mailto:allan@positiveenergysolar.com" target="_blank">allan@positiveenergysolar.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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Wrenches:<br>
We have cautiously agreed to take on a substantial upgrade and
rehabilitation of a poorly designed 48V off-grid system. Our upgrade
will include a substantial array addition, battery replacement, and
charge controller/safety disconnect replacement. But the immediate
need is for a generator. The 6 year old system has worn out two Onan
residential standby generators; the second one just now (at winter
solstice) has failed completely.<br>
<br>
We expect to keep the two SW5548 inverters. The site is at 7,800'
elevation. The fuel must be LP. The customer is willing to pay for a
high-quality unit. We expect only to specify or recommend the unit,
but not resell it, so there's no profit motivation involved; we just
want the best solution..<br>
<br>
I am looking for recommendations of a low-speed, liquid-cooled,
commercial- or industrial-grade LP generator, of at least 12kW and
preferably around 15kW, with a good reputation for long-term
reliability, and that is not designed for home standby use (with
phantom-load heaters and controls). It will be located outdoors, so
must have a weather enclosure.<br>
<br>
I occasionally am asked to answer this same question by Home Power
readers, who assume I know the answer because I wrote a primer on
generators for HP awhile back. Truth is, I don't have any good
recommendations in this size range, and I'm really hoping that some
of you experienced off-grid Wrenches who have done larger systems
can help here.<br>
<br>
Thank you,<br>
Allan<span><font color="#888888"><br>
<div>-- <br>
<font face="Times New Roman, Times, serif"><b>Allan Sindelar</b></font><br>
<small><a href="mailto:Allan@positiveenergysolar.com" target="_blank"><font face="Times New Roman, Times, serif" color="#000099"><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><a href="tel:505%20424-1112" value="+15054241112" target="_blank">505 424-1112</a></b><br>
<a href="http://www.positiveenergysolar.com/" target="_blank"><u>www.positiveenergysolar.com</u></a><u></u><u></u></span></font>
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