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

[ericstev at vermontel.net]

Wrenches, 

I am normally a lurker on the List, but I would like to add a fact
observation and a personal preference to the topics raised by this
discussion. 

First, THWN does have PVC as its primary insulation, but it is sheathed
in Nylon which is a polyamide plastic.  Therefore the compatibility with
MC4 connectors should be polyamide being squeezed by the restraining
bushing in the MC4, not PVC. 

I prefer Buchanan copper crimp connectors when splicing PV wire to
THWN-2 in a roof junction box.  The bared wires should be lightly doped
with NO-OX-ID A-Special grease
https://www.sanchem.com/electrical-contact-lubricant.html  before
sleeving and crimping with the crimp sleeve to repel entry of moisture
and corrosive gasses into the wire joint.  I consider the crimped joint
to be superior to any screw-clamped joint that would be made in a
Polaris style connector.  I also drill weepage holes in the bottom
corner of the junction box to mitigate any collection of water. 

Eric Stevens, Vermont Made Energy 

On 2021-04-28 18:16, re-wrenches-request at lists.re-wrenches.org wrote:

> I think the biggest issue with poor connections on the Polaris type blocks
> is not stripping enough insulation off the wire. They need much more
> stripped off than other types of connectors.  With too much insulation
> remaining, the screw tightens on the insulation, and the electrical
> connection is just some loose copper tickling the inside of the barrel.
> You wouldn't notice it at first with testing, but it would definitely start
> to over heat over time.  Might catch it with a FLIR though.
> 
> What other connectors are 1000 v rated?  This seems like more an issue of
> having the manufacturer's retest to 1000v.  I can't imagine those blocks
> not being able to handle 1000v, but.....
> 
> Ray Walters
> Remote Solar
> 303 505-8760
> 
> On 4/28/21 11:27 AM, Corey Shalanski wrote:
> 
> Chris's reminder is a good one?the 600V rating of most insulated
> "multi-tap" connectors pretty much limits their use to residential systems.
> I would also keep in mind that those connectors generally have a torque
> spec. I've definitely seen examples of meltdowns caused by poor
> terminations - either the compression screw isn't torqued properly or the
> conductor isn't fully inserted. To help eliminate the latter case, we used
> to favor the Burndy models (e.g., BIT4
> <https://www.hubbell.com/burndy/en/Products/Power-Utilities/Connectors/Lugs-Terminals/Bolted/Vinyl-Insulated/BIT4/p/2021315>)
> because they had a transparent case; I see that Polaris also now offers
> transparent models (e.g., IT-4C
> <http://www.nsiindustries.com/catalog/nsiproducts/polaris-mechanical-connectors/polaris-vision-tap/it-4c>
> ).
> 
> --
> Corey Shalanski
> Jah Light Solar
> Portland, Jamaica
> 
> On Wed, Apr 28, 2021 at 7:38 AM Chris Sparadeo <sparadeo.chris at gmail.com wrote: 
> Keep in mind that Wagos, Polaris lugs, Multi-tap Burndy lugs are rated
> for 600V. I can see this being a possible use for MC4 connectors in a
> higher voltage splice scenario, because of their 1000V/1500V ratings. 
> 
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> Today's Topics:
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> 1. Re: MC4s are listed for THWN, right? (Blake Gleason)
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Wed, 28 Apr 2021 15:13:51 -0700
> From: Blake Gleason <blake at sunlightandpower.com>
> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
> Subject: Re: [RE-wrenches] MC4s are listed for THWN, right?
> Message-ID:
> <CAJVVAurNwUhVTnE+QtqVMoC7kSa1DOB36L2UTDyyFeJ756Gz+w at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
> 
> Great discussion, all.  Thank you.
> 
> For 1000V (where we also tend to favor MC-style connectors), we are
> connecting PVWire to 1000V-rated XHHW-2 (which is not PVC), and always
> inside a 3R box.
> 
> Blake
> 
> On Wed, Apr 28, 2021 at 9:00 AM Ray <ray at solarray.com> wrote:
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