[RE-wrenches] AFCI disturbances.

[Bill Hoffer]

William

I agree with Bob-O, wire nuts are not the best choice for DC connections,
for all the reasons he mentioned,  but SMA claiming that wire nuts are
causing arc faults seems like a long shot at covering up an arc fault
detection nuisance tripping problem.  IMHO AFCI protection circuits are far
from perfected at this time and Inverters and optimizers have enough
inherent switching noise to cause nuisance tripping ( and there is ample
evidence supporting numerous inverter manufacturers having issues).  I
believe we are going to have similar growing pains as we did in the
beginning of requiring ARC Fault panel mounted breakers for bedrooms.  I
have since replaced all my Square D Arc Fault breakers due to failure, ie
nuisance tripping.  I understand the intent of adding arc fault to the 2014
code, but I am concerned that as installers we will again become the guinea
pigs in this crazy experiment!  Don't gt me started on the fact that they
are required to only detect series faults and that opening the circuit on a
 parallel fault will likely make the arc increase rather than extinguish!

Bill


On Wed, Jun 25, 2014 at 8:40 AM, William Miller <william at millersolar.com>
wrote:

> 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_wiring/_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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-- 
William Hoffer
161 SE Fourth Ave
P.O. Box 1823
White Salmon, WA 98672-1823
sunengser at gmail.com <bhoffer at sunergyengineeringservices.com>
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