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<div class="moz-cite-prefix">Hear, Hear, Carl.<br>
<br>
That has also always been my experience as well. In my off grid
work, reliability trumps budget, and I almost always over size
charge controllers, relays, inverters, fuse holders, etc. Most
failures seem to be related to pushing the design limits of the
equipment.<br>
I spent the past year working on multi MW systems, where they
saved every penny possible. The inverters were undersized by 20
to 25% but sitting in unairconditioned enclosures. Even better
that the projected 30 year life of the system did not even include
inverter replacements. <br>
I'm sure I shall be stoned to death for saying this, but basically
the grid tie solar community just doesn't have enough experience
under its belt yet to have seen what we learned a decade ago in
the off grid world.<br>
When they start putting call backs, down time, inverter
replacements, and the related loss of respect and business into
their spread sheets; they'll start oversizing the inverters more,
like you, Marco, and many of us already know.<br>
<br>
<pre class="moz-signature" cols="72">R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760</pre>
On 3/23/2013 7:19 PM, Carl Emerson wrote:<br>
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<p class="MsoNormal"><font face="Arial" size="4" color="blue"><span
style="font-size:
14.0pt;font-family:Arial;color:blue">Friends,<o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="4" color="blue"><span
style="font-size:
14.0pt;font-family:Arial;color:blue"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="4" color="blue"><span
style="font-size:
14.0pt;font-family:Arial;color:blue">I am a little puzzled
by this topic.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="4" color="blue"><span
style="font-size:
14.0pt;font-family:Arial;color:blue"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="4" color="blue"><span
style="font-size:
14.0pt;font-family:Arial;color:blue">What has happened to
the good engineering
practice of sizing electronic equipment so that it is not
driven to the maximum.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="4" color="blue"><span
style="font-size:
14.0pt;font-family:Arial;color:blue"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="4" color="blue"><span
style="font-size:
14.0pt;font-family:Arial;color:blue">My understanding is
that the MTBF
increases significantly the harder you drive the unit.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="4" color="blue"><span
style="font-size:
14.0pt;font-family:Arial;color:blue"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="4" color="blue"><span
style="font-size:
14.0pt;font-family:Arial;color:blue">This seems to be a
case of overdriving the
units for short term gain. <o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Arial" size="4" color="blue"><span
style="font-size:
14.0pt;font-family:Arial;color:blue"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><b><font face="Arial" size="3" color="blue"><span
style="font-size:12.0pt;font-family:Arial;color:blue;font-weight:bold">Carl
Emerson<o:p></o:p></span></font></b></p>
<p class="MsoNormal"><b><font face="Arial" size="3" color="blue"><span
style="font-size:12.0pt;font-family:Arial;color:blue;font-weight:bold">Free
Power
Co. <o:p></o:p></span></font></b></p>
<p class="MsoNormal"><b><font face="Arial" size="3" color="blue"><span
style="font-size:12.0pt;font-family:Arial;color:blue;font-weight:bold">Auckland
N.Z.</span></font></b><b><font face="Arial" size="4"
color="blue"><span
style="font-size:14.0pt;font-family:Arial;color:blue;font-weight:bold"><o:p></o:p></span></font></b></p>
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<p class="MsoNormal"><font face="Times New Roman"
size="3"><span style="font-size:12.0pt"> <br>
What I *can't* answer is the long-term effect this
may have on the overall<br>
life of the inverter. THAT depends on various
intricate design considerations<br>
that went into creating the inverter in the first
place.<br>
<br>
Dan Lepinski, Senior Engineer<br>
Exeltech / Exeltech Solar Products<br>
<br>
With 41 years experience as a design engineer in
solar energy.<br>
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