[RE-wrenches] Buchanan Crimp in 1000v Applications and the NEC

Tue Nov 11 15:59:53 PST 2025

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 <
re-wrenches at lists.re-wrenches.org> 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 <
> re-wrenches at lists.re-wrenches.org> 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 <
>> re-wrenches at lists.re-wrenches.org> 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 <
>>> re-wrenches at lists.re-wrenches.org> 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 <
>>>> re-wrenches at lists.re-wrenches.org> 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 <
>>>>> re-wrenches at lists.re-wrenches.org> 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 <
>>>>>> re-wrenches at lists.re-wrenches.org> 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>
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