It’s been my understanding that installing a cable to cable MC4 connection inside a junction box is against Stabuli manufacturer guidelines and that heat and moisture dissipation are important factors with MC4 connectors, even though they are IP68 rated. I remember hearing this reiterated at the NABCEP conference earlier this year as well.
On Tue, Nov 11, 2025 at 6:03 PM Jason Szumlanski via RE-wrenches < [email protected]> wrote: > We have had terrific success using Wagos in rooftop junction boxes for > splicing #12 Enphase cable to #10 home run THWN. We have no issues > whatsoever with these. > > Unfortunately, the #10 PV wire insulation is too large for the Wago > 221-6XX series. We have been buying #14-#4 Polaris taps and it's getting > very expensive. I would like an alternative. > > For a while we were using the King Innovation AlumiConn purple "suitcase" > connectors for Enphase, but they are only 300V rated and I don't think the > PV Wire insulation fits in those, either, for <300V applications. > > I have seen people using MC4 connectors in rooftop junction boxes like > Blake suggested, but I wasn't sure if that is acceptable practice to use > them this way (in an enclosure), and it does require a pretty large > junction box. We prefer to use the EZ Solar JB-# series of boxes. The rail > mount ones (JB-3) are pretty small, but the tile roof JB-2 is huge, and the > shingle JB-1 is sizable as well. I guess if there is no prohibition against > using them in an enclosure, then it should be allowed. I do like the > watertight nature of this solution. > > I have seen some clowns using MC4 connectors with #10 THHN wire to make > these splices. That's obviously no bueno. Crazy stuff... > > > Jason Szumlanski > Principal Solar Designer | Florida Solar Design Group > NABCEP Certified Solar Professional (PVIP) > Florida State Certified Solar Contractor CVC56956 > Florida Certified Electrical Contractor EC13013208 > > > On Tue, Nov 11, 2025 at 4:44 PM Dave Tedeyan via RE-wrenches < > [email protected]> wrote: > >> Hi Adam, >> This response is just to you. Is NYSERDA the inspection agency you are >> talking about? Cause they have given me issues about using Wago Nuts inside >> a 3R box, even after I got a statement from Wago saying that it is okay to >> put it inside a 3R box. But squirting a bit of No-Ox in there seems to make >> them happy about it. The one time we put one inside a 3R panel board to >> extend a short wire and forgot to put No-Ox on that one, they gave us a 2 >> out of 5 on the inspection, even though that was the only thing noted in >> the entire inspection report! But I would be curious if the point you make >> above will work with NYSERDA? >> >> Cheers, >> Dave >> >> On Tue, Nov 11, 2025 at 4:16 PM AE Solar via RE-wrenches < >> [email protected]> wrote: >> >>> We had an inspection agency that was giving us a hard time about using >>> buchanan crimps in junction boxes because they aren't rated for >>> outdoor/damp locations. The point was made (on this listserve) that "*if >>> the inside of a 3R enclosure isn't considered dry enough for a buchanan >>> crimp/cap, then there's millions of 3R panels with breakers and busbars in >>> them that would have the same problem*". The inspection agency finally >>> relented. We put a little No-Alox in the cap. I know that's not what your >>> initial post was about, but tossing that in for consideration just in >>> case... >>> >>> Adam Katzman (he/him) >>> Autonomous Energies | Owner/Operator >>> www.AutonomousEnergies.com <http://www.autonomousenergies.com> >>> (518) 567-1468 >>> >>> >>> >>> >>> On Tue, Nov 11, 2025 at 3:51 PM Jay via RE-wrenches < >>> [email protected]> wrote: >>> >>>> Hi Sam >>>> >>>> I can’t imagine being just copper it would matter, the AHJ might have a >>>> different opinion however >>>> >>>> Question. >>>> How are you insulating them? >>>> >>>> Jay >>>> >>>> >>>> On Nov 11, 2025, at 11:15 AM, Sam Haraldson via RE-wrenches < >>>> [email protected]> wrote: >>>> >>>> >>>> Wrenches, >>>> >>>> On the attached product spec sheet for Ideal Copper Crimps (aka >>>> Buchanan crimps) you'll see that max voltage for the crimp is rated at 600V >>>> but an asterisk indicates up to 1000V when "in fixtures and signs". In our >>>> application this is a 1000v system and we are joining pairs of #10 PV >>>> wires. The junctions are made in a rail-mounted, plastic j-box. We could >>>> not find the definition of "fixture" as it might pertain to this situation >>>> in the NEC and as such are interested to learn more about using Buchanan >>>> crimps for 1000V applications. >>>> >>>> <image.png> >>>> >>>> >>>> Cheers, >>>> Sam >>>> >>>> [image: OnSite Energy] <https://onsiteenergyinc.com/> >>>> >>>> Sam Haraldson >>>> Operations Specialist >>>> (406) 551-6135 >>>> 1515 N. Rouse Ave Bozeman, MT 59715 >>>> <https://www.google.com/maps/search/1515+N.+Rouse+Ave+Bozeman,+MT+59715?entry=gmail&source=g> >>>> Locally owned and operated since 2012 >>>> [image: B Corporation] <https://onsiteenergyinc.com/bcorp> >>>> <IDEALIndustries-Crimp Connectors.pdf> >>>> _______________________________________________ >>>> List sponsored by Redwood Alliance >>>> >>>> Pay optional member dues here: http://re-wrenches.org >>>> >>>> List Address: [email protected] >>>> >>>> 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/[email protected]/ >>>> 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 >>>> >>>> _______________________________________________ >>>> List sponsored by Redwood Alliance >>>> >>>> Pay optional member dues here: http://re-wrenches.org >>>> >>>> List Address: [email protected] >>>> >>>> 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/[email protected]/ >>>> 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 >>>> >>>> _______________________________________________ >>> List sponsored by Redwood Alliance >>> >>> Pay optional member dues here: http://re-wrenches.org >>> >>> List Address: [email protected] >>> >>> 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/[email protected]/ >>> 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 >>> >>> _______________________________________________ >> List sponsored by Redwood Alliance >> >> Pay optional member dues here: http://re-wrenches.org >> >> List Address: [email protected] >> >> 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/[email protected]/ >> 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 >> >> _______________________________________________ > List sponsored by Redwood Alliance > > Pay optional member dues here: http://re-wrenches.org > > List Address: [email protected] > > 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/[email protected]/ > 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 > >
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