DC Runs in the Attic [RE-wrenches] DC arc fault

[Matt Lafferty]

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Wrenches:

Drake asks:
  
>  Does anyone know of any real world problems that have developed
>  with runs through attics?

Just problems with Inspectors & Plan Checkers!  LOL  

This particular system didn't have wiring in the attic, but there was a
large junction box mounted directly below the roof at the gable.  Most of
the systems of the type in question (Atlantis SunSlates) do utilize "attic &
in-wall" wiring.  The principle applies to PV DC in general.

Seriously, we had one case locally where a smart-alec homeowner "thought" he
could tie straight into the homeruns to hook up some device or other a
couple of years ago.  He kept complaining that his system wasn't producing
as much energy as he "was promised".  He pulled this and other stuff for a
year and a half after the system was installed and operating so he could
avoid paying for it.  Due to the way we did things back then, he was able to
get away with it while getting free power the whole time.  (He was a big
incentive for getting procedures changed so we could avoid these things in
the future.  Not everybody can be trusted!)  This guy was a real piece of
work in more ways than one... Half-ass realtor.  OK, Matt.  No name calling!

After this year and a half, I was assigned to the problem.  Being the
dutiful Solar Janitor Guy, I went out to evaluate.  Several blown combiner
fuses... That's not normal.  Hmmmm (Combiner was at ground-level.
Batteryless SW with onboard combiner.).  I noticed some carbon residue
around the Big Blue Capacitor, but saw nothing out of order.  Everything
checked out electrically, but I felt it was prudent to investigate further,
not just replace the fuses and walk away.  Since it was "Take Your Kid To
Work Day", I arranged to return the following day.  (This was the day my
daughter learned to test fuses, for what it's worth.)

Upon returning, I got into the gable J-box.  I noticed different types of
wire nuts on some of the conductors and it looked like somebody had "gotten
into it after the installation".... 

Then I saw it!  There was a 1/2" hole drilled into the back of the J-box
when there was absolutely no reason for it to be there at all.  It took
quite a bit of coaxing and arm-twisting to convince him to let me get into
the attic.  I didn't tell him what I had seen.  I've dealt with beady-eyed
bastards enough in my life to know better.  

Anyway, what I found was a hunk of extension cord running from right behind
that J-box, across the attic, and down into some room or closet inside the
house.  The wire had been pulled back from the J-box, but the ends were
still stripped back.  I could see some "soot" residue on the conductor
insulation.  I never went down to investigate what might have been on the
other end of the extension cord.  I caulked the hole from inside the J-box,
then went fishing.

Fishing for answers that is.  In good ol' Southern fashion, I did a little
"head-scratching" and "Gee, I dunno" act.  Baiting him along, but never
telling him I saw the extension cord... Letting him think I was ignerrant,
but also letting him know I knew my stuff when it came to the PV System.
"Well, the only thing I can figger out is that somebody must have hooked
something up to some of the wires in that box up there.  Everything checks
out now and I can't find anything wrong, so I'll replace the fuses and put
this here meter on the system and we'll keep track of it for awhile."  

He never admitted anything, but I made it real clear that the PV stuff
wasn't suitable for hooking anything else up to it.  I have always believed
that he already realized this by that point.

In going back through the file, I found out that the Big Blue Capacitor had
in fact been a Big Blew Capacitor about a year before.  The service tech had
replaced it, and went on his way without checking the fuses.  It is my
opinion to this day that the Cap popped when this guy hooked into the J-box
and it took the fuses with it.  I've always laughed to myself over the
thought of him crapping his drawers when it went!  In this guy's case, it
was even funnier to think that it happened while he was standing on top of a
ladder, 25' off the ground.

Yes, we did finally get paid.  They guy sold the house and we haven't had
any problems with it since, to my knowledge.

The moral of the story is this: (I agree with much of what's been said
onlist about the topic)

A.  You don't know "who" will follow you into an attic at some point in the
future, or what kind of hair-brained stuff they will be thinking.  (AKA - Be
smarter than the dumba_ _!)
B.  Clearly identifying all PV conduits, wiring, J-boxes, disconnects, etc.
is STRONGLY advised!  (This applies to stuff that's not in the attic, too!)
C.  I don't support a "broad-brush" policy of "if it's PV, it can be run
anywhere and any way we want to".  This is flat out irresponsible.

I believe that there is a "worlds apart" difference between "large systems"
and "small systems" in terms of safety.  Appropriate measures and practices
to ensure reasonable safety "down the road" should be recognized and
determined accordingly. 

There is also a big difference between "high voltage" and "low voltage"
systems of the same wattage when something goes wrong.  (Arc welders operate
at low-voltage, high-current...)  

If there is a combiner in the circuit, "where that combiner is" relative any
portion of the circuit in question, becomes a significant factor.  (On the
output side, there ain't no way for any overcurrent protection to trip in
the event of a problem.  "You're just gonna have to wait until dark, Joe.
Let me know if I can get you anything in the meantime...") 

Disconnects should be installed in responsible locations.  When you think
about the cost, you can buy half a dozen disconnects for the price of a
single module.  I'm not advocating "overuse" of them, but if you're
installing a J-box or other accessible termination point in an attic, please
consider installing a disconnect very nearby.  

One other thing related to this:  If you are installing J-boxes or other
termination points in attics, install them in serviceable locations and
provide a light source!  (Like, install a little platform to stand or kneel
on...) I've been in too many spots in the course of inspecting and/or
servicing systems where just getting into them was not only awkward, but
potentially dangerous.  During the installation the wires may not be
energized, but they sure are later!  This issue seems to be rising in
frequency, especially on New Construction projects where the boxes get put
in before the drywall & insulation.  Since the installer can just set up a
step ladder directly below where the box is going and clearly see what he's
doing because, surprise surprise, "the sun is shining", he doesn't think
about "getting back into it after the fact".  Nobody ever seems to think it
will be necessary to "get back into something they did" because they always
think "they're perfect"... Go figure!  This isn't just a PV thing, it's the
nature and mentality of today's workforce in general.  

OK.  Back to work now...

Ya'll have a Safe & Sunny Day!

Matt Lafferty
Universal Energies Institute
mlafferty at universalenergies.com
(916) 422-9772
(916) 914-2247 Fax
www.universalenergies.com

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