You're right on the string sizing. My mistake. I was thinking IQ6+ vs IQ7+.
Mac makes a great point about the AC output rating and utilities. While the de facto (arbitrary) AC to DC ratio is 0.85x for the interconnection tier determination in Florida, I have one Co-Op that has agreed on a case by case basis to use the actual inverter output rating if it drops them down a tier, saving costs, insurance requirements, and the requirement for a disconnect switch. A 1.3x ratio means a 0.77x factor from the utility's perspective rather than 0.85x. FWIW, we have a lot of 1.3x ratios on M190s monitored out there. I have found no correlation between failure rates based on module watts. Admittedly, there were lots of M190 failures in general, but I don't see the ratio as a determining factor. Jason On Wed, Oct 7, 2020 at 10:09 AM Mac Lewis <maclew...@gmail.com> wrote: > Hi Jay, > > This is where a modeling program can really help. We use Helioscope to > model these (they let you try it for free) and extract the true benefit of > the more expensive inverter. Like Jason says, it's really all about the > environment, tilt & orientation etc. I have found there is also a > psychological component to a customer to see them clipping even if your > annual production estimates are right on. I haven't seen evidence that > Enphase life is compromised by overpowering them for many hours per day, > but we will see over time if that's true. Most of the time for non-ideal > roof mounts, we have found that an IQ7 will really lose very little energy > annually compared to the IQ7+. Like Jason, we have found no real reason to > use the IQ7A. > > There are other things to consider. For example, we have a utility > that puts fixed limits on the size of a solar system based on AC output of > the inverter. Oftentimes, dropping to an IQ7 allows a larger DC system and > thus more kWh to be produced. Stringing can change as well. > > Also, Jason according to the spec sheet you can put 16 of the IQ7 as > opposed to 13 of the IQ7+ on each string but maybe I misunderstood you. > > On Mon, Oct 5, 2020 at 5:42 PM Jason Szumlanski < > ja...@floridasolardesigngroup.com> wrote: > >> It depends on climate, orientation, and other factors. Here it is really >> hot almost all the time. We rarely experience anything close to the max >> power rating of a module here. If the orientation isn't ideal, that's >> another argument for oversizing. Around here we use 385 and 390W 72-cell >> modules on the 290W IQ7+ and rarely see clipping that would outweigh the >> advantages and cost-efficiency. Incidentally, early indications from some >> low temp coefficient 360W modules show that they do quite well compared to >> 385W modules with more standard coefficients this time of year. I need more >> data on that to make a real assessment. And modules with low temp >> coefficients tend to be pricey. >> >> I am very comfortable with 1.3x - 1.4x here in Southwest Florida using >> standard modules. Elsewhere I would expect the ratio to be somewhat lower. >> I have no justification for the IQ7A here at this time. >> >> P.S. My CED Greentech rep shared some Helioscope data using the IQ7 (not >> plus) and 360W 120-half-cell REC Alphas. There is only a marginal advantage >> to using the IQ7+ over the IQ7 in that scenario here. I still opt for the >> IQ7+ since it is marginally better when considering cost and performance >> and it is more compatible/flexible. Since it's the same max quantity per >> string, I don't see the point in dropping to the IQ7 for the price >> difference. >> >> Jason Szumlanski >> Florida Solar Design Group >> >> >> On Sat, Oct 3, 2020 at 8:08 PM Jay <jay.pe...@gmail.com> wrote: >> >>> Hi all >>> >>> For those working with Enphase. >>> How hard are people recommending pushing the DC/AC ratio? >>> >>> Enphase has some pretty convincing data that even a 400 watt module on a >>> 240watt inverter has very small clipping vs annual production >>> >>> Given that why would i recommend to a customer the IQ7A at 360va and >>> quite a bit more expensive vs the 240va IQ7? >>> Location would have something to do of course, tilt, yes. >>> But it seems that unless you’re installing a really large module or >>> their data is wrong, I’m not sure I see the advantage of the larger >>> inverter? >>> >>> I’m hoping there will be some counter views. >>> >>> Thanks >>> Jay >>> Peltz power. >>> >>> >>> _______________________________________________ >>> List sponsored by Redwood Alliance >>> >>> List Address: RE-wrenches@lists.re-wrenches.org >>> >>> Change listserver email address & settings: >>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >>> <https://mailtrack.io/trace/link/e83a1e73d57b258ff2b1d44f81d4a5a4220207f5?url=http%3A%2F%2Flists.re-wrenches.org%2Foptions.cgi%2Fre-wrenches-re-wrenches.org&userId=1613865&signature=bb1f4a383ae6936d> >>> >>> There are two list archives for searching. 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