Hi Blake - Greetings from across the Bay! We've been using the Buchanan/Ideal splice caps for approximately the last 5 years - they are awesome. As you mention, there is a lot of grey area in exactly what is appropriate in an outdoor box and rated for the various combos of wires we use in solar. That said, the splice cap crimp is solid, easy to visually inspect, and generally the most foolproof connection mechanism I've seen, especially compared to wire nuts and MC4 connectors. We still use MC4 connectors in our J-boxes if we have a system rated over 600 volts, but in that case we're not using THWN-2 anyway because we need wire with a higher voltage rating. For larger wires or applications where we're combining more wires, we're using the insulated multitap connectors such as those made by Polaris.
August Luminalt On Mon, Apr 26, 2021 at 5:40 PM Blake Gleason <bl...@sunlightandpower.com> wrote: > Corey, > > Thank you! Agreed, the message from Staubli's Eng dept is much less > confusing (with the exception of the statement about THHN tending to be > solid vs stranded). > > All - > What are you folks using to transition from PV Wire to THHN/THWN-2 inside > a junction box? We used to use split bolts, which make an awesome > electrical connection, but are time-consuming and not easily serviceable. > Wire nuts (the right ones) are Listed, but never felt reliable for that > purpose. Same for WAGO levers. I hear about people using Buchanan splice > caps, but I wonder about trading one set of crimping problems for another. > And of course, the only problem with using THHN in an MC4 is that the > compression gland may not be as watertight as it is with PVWire, and the > Buchanans certainly are not watertight. Terminal blocks generally aren't > listed, definitely aren't watertight, and raise inspectors' eyebrows. Why > is this so hard for me?? > > Best, > Blake > Thanks > > On Mon, Apr 26, 2021 at 5:19 PM Corey Shalanski <coreso...@gmail.com> > wrote: > >> Blake, >> >> In addition to Bryan's notes, here is some unconfusing information >> directly from Stäubli's engineering dept: >> >> The answer is categorically no: *you cannot use THHN wires with MC4 >>> connectors.* There are several reasons for this: >>> 1. *Certification*: our MC4 connectors are certified to UL6703, >>> which only covers UL4703 PV wire or USE2 cable. Any other wire type is not >>> covered by our certification >>> 2. *Internal validation*: we have no internal testing or validation >>> of how MC4 or Evo2 connectors perform with THHN cables. We therefore >>> cannot warranty / accept the use of THHN cables with our PV connectors. >>> The allowable cables and applications for our PV connectors is clearly >>> stated in the assembly instructions. >>> 3. *Construction*: THHN cables use very rigid PVC insulators, which >>> behave very differently than XPLE or TPE insulators that are the most >>> widely used on PV wires. PVC has a very low elastic range and easily >>> deforms permanently under load/thermal cycling. It is not a well-suited >>> cable for higher temperature or high temperature fluctuating applications >>> where compression-type cable seals (i.e. cable glands) are used. Also, >>> THHN cables tend to be single-conductor solid core cables, which are >>> absolutely not allowed with crimp terminations like the MC4 (or any other >>> PV connector on the market for that matter). They also are not allowed by >>> UL6703. >> >> >> These comments were forwarded to me by Jeff Wang, who works for Stäubli >> North America. >> >> -- >> Corey Shalanski >> Jah Light Solar >> Portland, Jamaica >> >> >> On Mon, Apr 26, 2021 at 9:23 AM <bl...@sunlightandpower.com> wrote: >> >>> >>> Bryan, >>> >>> Thank you for the link. I am confused by the "PVC" section you >>> referenced. Here's the complete text: >>> >>> For safety reasons Stäubli prohibits the use of PVC cables. Cables >>>> made from PVC can be connected to MC4-Evo 2 since the insulation material >>>> of the connector (Polyamide) is suitable to be connected to PVC. PVC cables >>>> usually have an upper limiting temperature of 70 °C, in fixed installations >>>> sometimes 80 °C. >>> >>> >>> THHN/THWN-2 is made with PVC insulation, so I assume that it falls under >>> the category of a "PVC cable." >>> >>> So, the first sentence seems to say that it's not allowed by Staubli. >>> But then the second sentence seems to say that is IS allowed. And then the >>> third sentence doesn't seem to be contemplating the most common PVC wire >>> type of all (in the US), which is THHN/THWN-2, which has a 90 degree >>> rating?! >>> >>> Can you help un-confuse me? >>> >>> Thank you! >>> Blake >>> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> Pay optional member dues here: http://re-wrenches.org >> >> 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 >> >> There are two list archives for searching. When one doesn't work, try the >> other: >> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ >> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >> >> List rules & etiquette: >> http://www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> http://www.members.re-wrenches.org >> >> > > -- > > Blake Gleason, PE | Employee Owner > Director of Innovation and Technical Excellence > O: 510-845-2997 x128 > C: 510-867-5878 > > 1035 Folger Ave. > Berkeley, CA 94710 > www.sunlightandpower.com > License #326203 > > <https://bcorporation.net/> <https://www.amicussolar.com/> > <https://calssa.org/> > > _______________________________________________ > List sponsored by Redwood Alliance > > Pay optional member dues here: http://re-wrenches.org > > 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 > > There are two list archives for searching. 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