An update on this long-running saga:
Enecsys' promised written report has not materialised yet, as I write, but in fairness the person writing it is based on the East Coast of USA where it is still Thursday, so (arguably) their report is not (yet) late!
However, I have just today received some interesting information from Sanyo, from which I will copy the most interesting parts.
Sanyo's stated position is that they "just make the panels, what happens to them after that is someone else's responsibility entirely".
The first interesting thing is the sub-division of the HIT-H250E01 panel by its bypass diodes - into 3 but not into "thirds" after all:
The slightly more detailed specification, provided in the Installation Manual, describes the panel as having 240 "cells", with 60 "cells" in series, so that each "cell" is only a quarter of a "hexagon". This then explains how they can show straight boundary lines between the diode sub-divisions of this panel. Clearly, this has the potential to trigger an avalanche (sorry for the pun!) of comment about how the shading of individual installations will affect output, but at least we now have (some of) the facts ....
And for comparison, the equivalent picture for Sanyo's "conventional" HIT-N235SE10 panel - which divides into thirds exactly as assumed:
Sanyo also sent me the Installation Manuals for both the above panels.
These are PDF files, and the filesize is bigger that 128 kB, so too big to attach to this post.
PM me if you need it urgently, or else contact your installer, or Daniel Roca at Sanyo directly: <
daniel.roca@sanyo-solar.eu>
The aspects most relevant to previous discussions (on thread: http://www.navitron.org.uk/forum/index.php/topic,15992.0.html) are the following, which I shall be taking up with Enecsys, depending on what their report actually says, when it actually arrives.
Under "NOTES ON SPECIFICATIONS" in the Installation Manual for the Sanyo HIT-H250E01 panels, Sanyo stipulate that, because of the potential for upwards tolerances on panel outputs:
"the values of Isc and Voc marked on this module should be multiplied by a factor of 1.25 when determining component voltage ratings, conductor current ratings, fuse sizes, and size of controls connected to the module output". Thus (according to this Sanyo specification anyway) neither of the Enecsys SMI-240-G83 60-cell or 72-cell micro-inverter units is 100% appropriately matched to the Sanyo HIT-H250E01 panel in respect of BOTH voltage AND current rating:
Sanyo HIT-H250E01 Enecsys Enecsys
60-cell 72-cell
max Voc = 43.1 x 1.25 = 53.9 V 43 V 54 V
max Isc = 7.74 x 1.25 = 9.68 A 12.0 A 8.9 A
However, Sanyo's NOTES ON SPECIFICATIONS does go on to say, in the immediately following paragraph:
"The current output for the modules shown in the Specifications is measured at Standard Test Conditions. These conditions may not be frequently observed in actual practice". Possibly therefore, Enecsys may have considered this infrequency of maximum current event to be their "get-out clause" when deciding that the Imax = 8.9 A of their 72-cell unit is "probably OK" (with just 15% over-current capacity rather than the 25% that Sanyo stipulate), while at the same time considering that the Vmax = 43 V of the 60-cell unit is "definitely not OK" (with zero over-voltage capacity).
Nevertheless, according to PVGIS, most of us will be expecting just over the 1000 W/m2 of STC (Standard Test Conditions) at midday on any clear day in April, and pretty close to 1000 W/m2 at midday throughout the summer months. No-one will deliberately want to take any significant risk of running their micro-inverters "too hot" for even a few hours a day, for several months of the year, for the next 25 years, notwithstanding the 20 year guarantee from Enecsys, if there is an alternative.
But then I looked at the equivalent over-current and over-voltage calculations for the "conventional" 72-cell Sanyo HIT-N235SE10 panel, which had been my original choice:
Sanyo HIT-N235SE10 Enecsys
72-cell
max Voc = 52.4 x 1.25 = 65.5 V 54 V
max Isc = 5.85 x 1.25 = 7.31 A 8.9 A
Which doesn't match either, and (given that we are now looking at a 72-cell panel with a 72-cell micro-inverter) this leaves me more confused than before. Although in fairness, when this was discussed in the above-mentioned long thread, I did not know of the 25% margin stipulated by Sanyo.
I can only wait and see how, in their report, Enecsys choose to describe their published Vmax and Imax ratings, whether they consider any uplifted value, stipulated to allow for tolerance on panel output, should lie below their published ratings for the micro-inverters, or whether their nominal published ratings have already taken into account the full potential effect of such uplift beyond the nominal published panel output values?
Of course, none of the above addresses the other big issue, which was the MPPT operational voltage range of the Enecsys microinverters when compared with the Vmp for the Sanyo panels:
Enecsys SMI-240-G83 60-cell: MPPT = 21 - 35 V
Enecsys SMI-240-G83 72-cell: MPPT = 29 - 42 V
Sanyo HIT-H250E01 (60-cell): Vmp = 33 - 35 V
Sanyo HIT-N235SE10 (72-cell): Vmp = 40 - 44 V
But any further discussion of that aspect really must wait until I have seen what their report says.
Watch this space ..... hopefully for not very much longer, but I wouldn't hold your breath!
[Edited several times after posting ..... sorry Gavin]
