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<font face="Verdana">This should not be troubling at all. It is very
straight forward.<br>
<br>
Because there is only one module per inverter, and the conductors are
sized for all possible overcurrent conditions, no further consideration
is necessary for the DC side of the circuit.<br>
<br>
For the ac side, section 690.8(A)(3) applies. "Inverter Output Circuit
Current. The maximum current shall be the inverter continuous output
current rating."<br>
<br>
So, for an M190-240 this is 0.8A. A fully loaded branch of 15
inverters is 12A, times 1.25 yields a 15A breaker.<br>
<br>
Do you think we should provide more documentation on this subject? All
suggestions for improved documentation, whitepapers, app notes, etc.
are very welcome.<br>
<br>
</font>
<pre class="moz-signature" cols="72">See ya!
Marv
707 763-4784 x7016
</pre>
<br>
<br>
Mark Westbrock wrote:
<blockquote cite="mid:4BE4B92E.7070805@positiveenergysolar.com"
type="cite">
<meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type">
The "Maximum Output Power" listed on the M190 spec sheet is 190 watts.
Upon observing output exceeding 190 watts, we questioned Enphase tech
support and were told that the "actual" max output is 199 watts.
Similarly, the actual max output for the M210 is reported to be 219
watts, although the spec sheet specifies 210 watts. This contradiction
between "specified" and "actual" is troubling, both for proper overall
system design and proper sizing of overcurrent protection, per
690.8(B)(1).<br>
<br>
<pre class="moz-signature" cols="72">Mark Westbrock
NABCEP Certified Solar PV Installer
NM ER-1J Journeyman Electrician
Positive Energy, Inc.
office: 575-524-2030
cell: 575-640-2432
<a moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="mailto:westbrock@positiveenergysolar.com">westbrock@positiveenergysolar.com</a>
<a moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="http://www.positiveenergysolar.com">www.positiveenergysolar.com</a></pre>
<br>
<br>
Chris Worcester wrote:
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<div class="Section1">
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Do
the Enphase inverters clip the output power to their rating
like other manufacturer’s? So a M190 can only put out 190 watts max? I
have had this question for a bit now on system performances using
Enphase in
designs during our cold spring and fall days.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Calibri","sans-serif"; color: navy;">Sincerely,<br>
<br>
Chris Worcester<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Calibri","sans-serif"; color: navy;">Solar
Wind Works<br>
NABCEP Certified PV Installer<br>
Phone: 530-582-4503<br>
Fax: 530-582-4603<br>
<a moz-do-not-send="true" href="http://www.solarwindworks.com/">www.solarwindworks.com</a><br>
<a moz-do-not-send="true" href="mailto:chris@solarwindworks.com">chris@solarwindworks.com</a><br>
"Proven Energy Solutions"</span><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p></o:p></span></p>
</div>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<div>
<div
style="border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p class="MsoNormal"><b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">From:</span></b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">
<a moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>]
<b>On Behalf Of </b>Mark
Westbrock<br>
<b>Sent:</b> Friday, May 07, 2010 10:33 AM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] Enphase performance<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The over-reporting of energy that Randy refers
to below was
much higher than any discrepancy based on monitoring resolution. We
have
a pyranometer at the site, and Enphase reported energy production as
high as
38% higher that predicted from irradiance data, as well as 38% higher
than the
string inverter portion of the same system. Individual microinverters
showed instantaneous power output as high as 285 W from a nominal 190 W
unit.<br>
<br>
Enphase explained that there was a software glitch that was resulting
in
"double counting". It took them over two months to correct this
issue, time which is lost from our experimental comparison of string
vs.
microinverter. They indicated that this seemed to be an isolated
situation,
but I wonder how many Enphase customers are reporting miraculous
performance
from their system without verifying via another meter.<br>
<br>
Screen shot of a day's power production of 22 M190 microinverters
(nominal 4180
watts AC):<br>
<img id="_x0000_i1025"
src="cid:part1.05010409.01050805@enphaseenergy.com" border="0"
height="286" width="469"><br>
<br>
Mark<br>
<br>
<o:p></o:p></p>
<pre>Mark Westbrock<o:p></o:p></pre>
<pre>NABCEP Certified Solar PV Installer<o:p></o:p></pre>
<pre>NM ER-1J Journeyman Electrician<o:p></o:p></pre>
<pre>Positive Energy, Inc.<o:p></o:p></pre>
<pre>office: 575-524-2030<o:p></o:p></pre>
<pre>cell: 575-640-2432<o:p></o:p></pre>
<pre><a moz-do-not-send="true"
href="mailto:westbrock@positiveenergysolar.com">westbrock@positiveenergysolar.com</a><o:p></o:p></pre>
<pre><a moz-do-not-send="true"
href="http://www.positiveenergysolar.com">www.positiveenergysolar.com</a><o:p></o:p></pre>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style=""><span style="color: rgb(31, 73, 125);">We
definitely experienced an overstatement. </span><o:p></o:p></p>
<p class="MsoNormal" style=""><span style="color: rgb(31, 73, 125);"> </span><o:p></o:p></p>
<p class="MsoNormal" style=""><span style="color: rgb(31, 73, 125);">We
have a client who installed 5kW on a string inverter
and 5kW on enphase and it is that side-by-side comparison that enabled
us to
positively identify a problem. There was a significant overstatement of
output.
We finally got a Enphase person who told us it was a software glitch.
The
problem appears to be fixed. They explained to us that our problem was
isolated without giving us a detailed explanation of what happened.
Since
that problem was fixed, we have seen no difference in output between a
string
inverter and enphase.</span><o:p></o:p></p>
<p class="MsoNormal" style=""><span style="color: rgb(31, 73, 125);"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">Randy<br>
<br>
</span>Kirpal Khalsa wrote: <o:p></o:p></p>
<p class="MsoNormal">This same issue has come up over the years for
us......first
with PV Powered inverters and then noticed in Fronius as well......We
have
noticed in most of our grid tied systems that are connected thru a
"revenue grade meter" for Oregon Energy Trust production reporting,
that the inverter always has a higher performance than indicated on the
"utility grade meter". We have seen the discrepency as
high as 10%. Over time this adds up to significant kWh
differences. In our experience the inverter always has the higher kWh
reporting, we have attributed this to the inverter wanting to report a
good
production number, to boost their efficiency claims......maybe even
more than
is accurate.....I have asked PV Powered and Fronius about this and
their line
is that to put a "revenue grade meter" into the inverter would be
cost prohibitive......interesting as the readily available revenue
grade meters
are only $30-$60. I would gladly pay that much extra if I didn't
have to wire in an additional meter. <br>
I don't think this problem is unique to the Enphase units (i haven't
installed
any of these), I think all inverters should be required to install the
revenue
grade meters to give accurate reporting of actual production.
Similar to how states have a "weights and scales" accuracy
certification, energy consumption and production meters should be
similarly
calibratable. <br>
<br>
-- <br>
Sunny Regards,<br>
Kirpal Khalsa<br>
NABCEP Certified Solar PV Installer<br>
Renewable Energy Systems<br>
<a moz-do-not-send="true" href="http://www.oregonsolarworks.com">www.oregonsolarworks.com</a><br>
541-218-0201 m<br>
541-592-3958 o<br>
<br>
<o:p></o:p></p>
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