William, My team and I are constantly strategizing about the issue you have described, pretty much on a project-by-project basis nowadays since our module supplier's stock changes frequently. Each new module's lead cable positioning and lengths must be examined for compatibility with the specified MLPE device. Our process typically involves creating a CAD sketch of the wire management details, aiming to follow the 2020 NEC securement rules (within 12" of each junction box, spans not to exceed 24" elsewhere) as closely as possible. We have come to the determination that certain module lead cable configurations are simply not 'MLPE-friendly'; in particular, modules with split junction boxes and short lead cable lengths (≤ 250 mm) appear to be tailor made for non-roof-mounted arrays where rapid shutdown devices are unnecessary. I wish I could say that we avoid using those modules for rooftop arrays, but the truth is that we sometimes don't have the option to pick-and-choose a certain project's spec module. There are definitely times when the cables on the module and the cables on the MLPE aren't quite long enough to connect to each other—for those times, as Jay suggested, we will specify jumper cables to make up the difference.
We have found the design of the APsmart RSD-S-PLC <https://apsmartglobal.com/wp-content/uploads/2021/11/4301615202_RSD-S-PLC-Datasheet_Rev2.3_2021-11-11-1.pdf> to be one of the more flexible (and less visually obtrusive) options. With the input/output cables extending to either side of the device (*along* the module frame as opposed to *away from* it), they seem to be better suited to the 'long-edge leaded modules' you describe on your web page. -- Corey Shalanski Jah Light Solar Portland, Jamaica On Fri, Mar 25, 2022 at 3:22 PM William Miller <[email protected] > wrote: > > Friends: > > > > I have been designing a large-ish off-grid system over the last few > weeks. This will be our first off-grid system to require MLRSS. We chose > the Tigo TS4-A-F system. > > > > In order to make certain the Tigo will work with modules that we can get > our hands on, we brought in a few samples to try and connect with the > Tigos. What we found is that with many of the new PV panels, the leads > connect to the two long sides of the panels and are often too short to > practically route to the frame-mounted Tigos. > > > > This got me to thinking: Many panels are now configured with leads > connected to the two long sides. Many new panels are coming out with > shorter leads. Virtually all new roof-mounted installation will need some > form of MLPE. These new panels will be ill-suited to connect to those MLPE > devices. > > > > This has to do with the fact that instead of in the old days, when each > panel connected to a neighbor on either side, each panel now connects to a > single device, the MLPE. The leads must able to reach that MLPE without > being pulled, banjo-string-tight across a void. If PV leads cannot be > supported, they will end of laying on the roof. Can we agree that is a bad > thing? > > > > Have any of you consider this situation? It is kind of complicated and > hard to explain. I attempted to do so by writing a web page dedicated to > the subject. I finished the site today but I am not sure it communicates > the dilemma adequately. You can find it here > <https://millersolar.com/MillerSolar/case_studies/31-Module_leads/Module_leads.html> > . > > > > I would be most grateful if some of you more experienced installers could > look this over and let me know if this problem has come across your radar > and what you are doing about this issue. > > > > Thanks in advance. > > > > William Miller > > > > Miller Solar > > 17395 Oak Road, Atascadero, CA 93422 > > 805-438-5600 > > www.millersolar.com > > CA Lic. 773985 >
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