I don't know of any explicit prohibition, but the assembly instructions state:
“Install the connector in such a way that sufficient heat dissipation is ensured.” That's open to interpretation and they don't indicate what is "sufficient." Something about it doesn't sit well with me, so I have refrained from using MC4s in enclosures of any type, but that doesn't mean it's not allowed, and it might be perfectly safe and functional. I would be interested in learning anything more on this topic. 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, 6:49 PM Blake Gleason via RE-wrenches < [email protected]> wrote: > Chris - interesting. Do you have any documentation from Staubli about > this restriction? I haven't seen anything like that myself. Thanks, Blake > > On Tue, Nov 11, 2025 at 3:43 PM Chris Sparadeo via RE-wrenches < > [email protected]> wrote: > >> 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. 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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 >> >> > > -- > > Blake Gleason, PE | Employee Owner > Director of Innovation and Technical Excellence > O: 510-845-2997 x128 > C: 510-867-5878 > [image: sunlightandpower.com] <http://sunlightandpower.com/> > > <https://linktr.ee/SLP_Socials> > > 1035 Folger Ave. > <https://www.google.com/maps/search/1035+Folger+Ave.+Berkeley,+CA+94710?entry=gmail&source=g> > Berkeley, CA 94710 > <https://www.google.com/maps/search/1035+Folger+Ave.+Berkeley,+CA+94710?entry=gmail&source=g> > www.sunlightandpower.com > License #326203 > > <https://benefitcorporationsforgood.com/> [image: > https://www.amicussolar.com/] <https://www.amicussolar.com/> [image: > https://calssa.org/] <https://calssa.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. 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