[RE-wrenches] MC4s are listed for THWN, right?

Tue Apr 27 14:55:25 EDT 2021

Hi Jason - I noticed that Tesla is using the Wago connectors in their
Powerwalls. They only go up to #10, but they certainly appear to have some
advantages such as easy QC inspection, compactness, and price. We are in
the process of trying a batch of these out, but I hadn't considered using
them in exterior J-boxes.

https://www.wago.com/global/electrical-interconnections/discover-installation-terminal-blocks-and-connectors/221

August

On Tue, Apr 27, 2021 at 10:42 AM Jason Szumlanski <
jason at floridasolardesigngroup.com> wrote:

> I'd be interested to hear thoughts on Wago 221-6XX series connectors,
> specifically for THWN to Enphase IQ/DG/TC conductor transitions or just
> THWN splices.
>
> On Mon, Apr 26, 2021, 8:40 PM Blake Gleason <blake at 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 <coresolar at 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 <blake at 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
>>>>
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>>
>> --
>>
>> 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
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>>
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