[RE-wrenches] AFCI disturbances. wire nuts

[August Goers]

Hi All -

We have been using outdoor Ideal brand wire nuts (the blue ones packed
with waterproof gel/grease) for all of our residential DC side splices
(typically #10 wire) for 10 years now and have never had a single problem.
If the installers properly strip the conductors and follow the
instructions I feel that these wire nuts make very robust connections. We
always do a good pull test after twisting the wire nut on. I would never
recommend standard wire nuts without the grease and have seen these fail
numerous times during inspections of systems installed by others.
Insulated terminal blocks also work well but don't have that nice
waterproof grease in them to help avoid moisture issues. You can wrap them
with a good splicing tape to help keep moisture out but the cost for these
connections is significantly higher than wire nuts:

http://solutions.3m.com/wps/portal/3M/en_US/EMDCI/Home/Products/Catalog/~?
N=5433135&rt=c3

Normally I error on the robust conservative side of the installation
spectrum but in this case it sounds like I may not.

Just my $0.02

Best, August


-----Original Message-----
From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
Behalf Of William Miller
Sent: Wednesday, June 25, 2014 8:40 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] AFCI disturbances.

Richard:

Possibly. I think I prefer din mount connector blocks. However, if a wire
nut can arc internally a connector block might also. I am still wondering
about this concept.

William

Miller Solar

> On Jun 25, 2014, at 6:09 AM, Richard.L.Ratico at valley.net (Richard L
Ratico) wrote:
>
> William,
> Would UL listed crimp sleeves be an acceptable substitute where you
> would otherwise use wirenuts?
>
> Dick Ratico
> Solarwind Electric
>
>
> --- You wrote:
> Bob-O:
>
>
>
> When you say verboten, what does that mean?  Not kosher?  Frowned upon?
> Disallowed by law???
>
>
>
> I am quite curious about this subject.  Here is what I have learned so
far:
>
>
>
> This is a unique case where we are replacing 3 dead SMA U series
> inverters with 2 US series inverters.  The U series seem to all be
> dying at about 12 to 14 years of age.  We have about a dozen of these
> to swap on our calendar and expect more.  It may be that to do this
> right requires that we pull new wire from the arrays.  This makes the
job a lot more expensive.
>
>
>
> We have never used a wire nut on a PV lead until this project.  It's
> not that we disapprove of wire nuts in general, it is because we know
> that if we were to use them regularly we would eventually have failures
and call backs.
> We allow only one splice in a PV lead: between the cable provided by
> the manufacturer of the module and a bulkhead mounted MC4 connector
> direct to THWN in conduit
> (http://millersolar.com/MillerSolar/practices/PV_wiring/PV_Cable_wirin
> g/_PV_
> Cable_Wiring.html).
>
>
>
> We checked the manufacturer's listing and the wire nuts are rated for
> 600 volts.  We do use wire nuts on AC circuits, such as switch and
> receptacle circuits in a power room.
>
>
>
> A tech at SMA told me that wire nuts "arc internally to the spring"
> causing the AFCI faults.  I am not aware of any process of "internal
> arcing."  To me, arcing means, as per the dictionary definition: "a
> luminous bridge formed in a gap between two electrodes."  The same
> tech told me to solder the leads and apply shrink tubing.  I don't
> believe this is an approved method.  By the way, we have spliced leads
> on both US series inverters and only one is exhibiting AFCI
disturbances.
>
>
>
> I do favor mounted terminal blocks, either screw or tubular type. I
> need to check if the Amp model we stock are 600 volt rated.
>
>
>
> I was told by another representative from SMA that on a ground-mount
> system it is legal to disable the AFCI protection.
>
>
>
> I will be troubleshooting this job tomorrow and I will let you all
> know what I learn.
>
>
>
> William Miller
> --- end of quote ---
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