[RE-wrenches] Polaris gone bad?

Mon Apr 10 13:24:28 PDT 2017

Hi all,

We also like making these splices with MC connectors.  We already have the
tools and parts, installers are good at it, the connection is solid, and it
has the added bonus of improving maintenance/troubleshooting/commissioning
because the splice is easy to separate and check.  We used to use split
bolts, but cutting open all of the tape to megger the homeruns is a pain.

The only downside to the MC connector method for small numbers of strings
is that you need a larger j-box to accommodate them.  For a handful of
strings, use a short 4x4 gutter.

Blake

Blake Gleason, PE, LEED AP
Director of Engineering
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On Mon, Apr 10, 2017 at 12:48 PM, <eric at harvesthesun.com> wrote:

> Good discussion here. I will not rule out loose connections entirely but I
> will say that our installers know that can be an issue and really tighten
> their connections. I like William's suggestion of fabricating an MC-type
> connector at the PV Wire to THWN transition. At least I presume that's what
> he's suggesting. Indeed we've moved away from the screw-type Polaris and
> are not interested in the old-fashioned wire nut. We're 100% Sunpower and
> they recommend the Buchannon's so that's what we're installing today.
> However, I'm going to investigate the Miller method. William has never led
> me astray!
>
> Eric Stikes
> SunHarvest
>
>
>
> --------- Original Message ---------
> Subject: Re: [RE-wrenches] Polaris gone bad?
> From: "William Miller" <william at millersolar.com>
> Date: 4/8/17 2:48 pm
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
>
>
> Wrenches:
>
> I am wondering why the proliferation of splices in PV leads?  We all know
> splices are a weak link.
>
> We allow only one connection between a module and the feeder destination--
> be it a combiner, inverter or optimizer-- and it is an MC connector, one
> side of which is factory-made and provided by the module manufacturer.
>
> If one plans and pulls PV circuits with forethought, splices should not be
> necessary.
>
> If anyone wants to know more about how this can be accomplished, look at
> our web site or contact me off list.
>
> William
>
> On Apr 8, 2017, at 10:05 AM, Glenn Burt <glenn.burt at glbcc.com> wrote:
>
> It is also worth noting that many of the SMA installation manuals
> specifically say do not use wire nuts on DC wiring.
> Of course choosing to ignore the manufacturers installation instructions
> would be a NEC violation.
> ------------------------------
> From: Drake <drake.chamberlin at redwoodalliance.org>
> Sent: ‎4/‎8/‎2017 12:10
> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
> Subject: Re: [RE-wrenches] Polaris gone bad?
>
>
> At 01:35 PM 4/6/2017, you wrote:
>
> Recently we interfaced with another solar install firm that has gone back
> to wire nuts due to this same problem.
>
>
> Wire nuts have the advantage of holding the wires tight with a spring. The
> spring follows the cold flow of the copper over the years. A screw type
> connection does not.
>
> When I service an old breaker box, usually the wires are loose under the
> screw connections, especially on the neutral and grounding bars. Often they
> are very loose, and I bet that the screws were tight after the initial
> installation of the equipment.
>
> On old industrial control equipment, I've learned the hard way to tighten
> all screws before doing anything in the box, as wires are prone to fall out
> of the loose screw connections. Again, these connections have the weakness
> of being held by terminal screws, with no spring to follow the cold flow of
> the metal.
>
> With wire nuts, it can be a bit tricky to know if you have a good
> connection, as the connection is hidden under the plastic cap. It is good
> to pull hard on each wire separately to be sure it is securely under the
> spring. It is crucial never to mix copper and aluminum under a wire nut
> unless it is one specifically designed for the purpose. Unless specifically
> listed, all out door wire nuts should be in a weather proof box, and
> preferably taped.
>
> Drake Chamberlin
>
>
>
>
>
> *Athens Electric LLC OH License 44810 CO License 3773 NABCEP Certified
> Solar PV 740-448-7328 <(740)%20448-7328> *http://athens-electric.com/
>
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