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<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009>Hi Keith,</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009>Both hands up here. From day 1 in
PV.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009>Every single field-installed current carrying conductor
to the point of termination. AC & DC. BEFORE energizing them!
</SPAN></FONT><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009>One megger lead on the conductor, the other on the
raceway or ground-wire. </SPAN></FONT><FONT face=Arial color=#0000ff
size=2><SPAN class=937552300-28042009>Megger @ 1kV. Must be greater than 250
Megohms to pass. Record the values on your commissioning
sheet.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009>I only meggered the actual arrays on projects where it
was a requirement and I only did that following specific procedures
provided by the module manufacturer. No procedure from the mfr = No array
megger.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009>I believe it's a critical thing to do as part
of the commissioning. But then again, I don't like ground faults or
fires.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009>I'll never forget a couple of head scratchers that the
megger found.... One was a perfectly fine, 6' long piece of Orange #12
XHHW-2 that would only pull 40 Megohms installed in EMT. Pulled it out and
replaced it. Inspected it for any visible flaws. None found. Not a scratch or
scuff. Used it as a training tool for my guys. Hung it on the wall over my desk
as a handy reminder. If anybody wants a picture...</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009></SPAN></FONT><FONT face=Arial color=#0000ff
size=2><SPAN class=937552300-28042009></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009></SPAN></FONT><FONT face=Arial color=#0000ff
size=2><SPAN class=937552300-28042009>The other was interesting, too. The very
first PV system I ever installed. </SPAN></FONT><FONT face=Arial color=#0000ff
size=2><SPAN class=937552300-28042009>Was shooting the DC circuits from the
inverter all the way to the connector on the output jumper cables at the
modules. Megger showed dead short on one wire. Fluke 79 on ohms showed
clear. Hit it with the megger again. Dead short. </SPAN></FONT><FONT face=Arial
color=#0000ff size=2><SPAN class=937552300-28042009>I'm known
for being anal about conduit and wire installation, so this was quite
unexpected, not to mention a little embarrassing. <FONT face=Arial color=#0000ff
size=2><SPAN class=937552300-28042009>This happened to be a Solarex Millennia
Integra system with an Omnion inverter and the array happened to be scattered
all over this roof. For those of you who who have dealt with that situation,
you'll understand what a cluster-*$#! that is... Especially being my very first
PV system and all... I wasn't anywhere near confident that I had a clue by
that point. All ready to see my first install fire up and this
happens.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009></SPAN></FONT> </DIV></SPAN></FONT>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009>It was my first install and I had 3 people getting paid
prevailing wages to learn... I was learning too, but I wasn't making anywhere
near prevailing wages, let me tell ya. </SPAN></FONT><FONT face=Arial
color=#0000ff size=2><SPAN class=937552300-28042009>Well, it was early January,
late in the day and foggy as foggy gets, but we went back onto the roof anyway.
Yeah... Overtime for everybody but me. We o</SPAN></FONT><FONT face=Arial
color=#0000ff size=2><SPAN class=937552300-28042009>pened up the condulets and
J-boxes for inspection. Pulled all the wires up out of the J-boxes. Pulled the
endcaps and ground clips off <EM>(unique components of the Integra
product)</EM>. Couldn't find anything suspicious. Shot it with the megger again,
and it was all clear. But no sign of anything that could have been shorted. We
put everything back together and shot it again. Dead short!
Aiyeeeee!</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009>Call it a day. <SPAN class=937552300-28042009>Go home.
I couldn't get back to that site until about the same time the next day. Foggy
again. Only took 1 helper with me this time. We completely repeated the entire
exercise, with exactly the same results. By now, I was pretty sure this
solar stuff wasn't my calling. I've always been regarded as a
gifted trouble-shooter and all I could say at this point was that I didn't
know _____! All signs pointed to it being associated with one of the J-boxes or
the endcaps or the ground clips, but there was NOT a thing we could see.
</SPAN></SPAN></FONT><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>Oh, well. I would have
to come back another day. When I went back, I took the same helper and made sure
I had all day if necessary to fix the problem. No matter what it turned out to
be. We planned to take it apart 1 piece at a time and re-shoot it
with the megger after each step. I left my helper on the ground with the megger
while I took it apart on the roof, 1 screw at a time.
Again.</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>Well, lo and behold, he
hollers up that "It's clear" when I pulled the cover off one of the 2-gang bell
boxes. Hadn't moved a wire. Just took the cover off. Let me tell ya, I stuck my
nose and four eyes in that box real close, but didn't touch any wires. The box
was a tight fit with those big, sealant-filled blue wire nuts that came with the
Solarex Kit, but I still couldn't see anything wierd.</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>"Shoot it
again."</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>"All clear,
boss."</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>I put the cover back on
and installed all the screws. "Shoot it again."</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>"Dead short." We had a
talk later about shouting things like "Dead short" on the jobsite, but I won't
get into all that right now.</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>I took out one of the
cover screws. "Shoot it again." Same answer from the
ground.</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>I took out a second
screw. "Shoot it again." This time the reply was different. I took out the third
screw and we repeated the process. Still clear. And the fourth. Still clear.
WTF? I lifted the cover for what seemed like the hundredth time. I studied
the nested wires, all neatly and systematically put into what I had thought
would be their final resting place... Days before and time and time again at
this point. </SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>I began
g</SPAN></SPAN></FONT><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>ently lifting the
wires out so they all stood up like dandelions in a spring lawn. I inspected
them for the nth time. Looking for a stray strand outside its protective hat.
Nope. Overtightened wire nut with the spring or a conductor coming out the tip?
Nope. But what's this little, nearly imperceptible dent in the side of this wire
nut? As I looked closer, I could see that it was round, flat bottomed and about
the same diameter as a 6-32 screw. Hmmmm. I rolled the wires back into their
resting position. Uh, huh. This particular wire nut's natural home was directly
under the cover screw which had cleared the fault when removed and the dent
lined up perfectly. The screw could just barely be long enough to pierce the
plastic and contact the wire-spring. </SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>I replaced the wire nut,
repositioned the conductors to make sure we wouldn't have a repeat, and buttoned
up the J-box. I put the wirenut in my pocket for later reference. One more
megger shot proved the system to be all clear. We could now energize the DC and
do our Voc & Isc testing prior to startup. Thank goodness the sun was
shining. I wasn't happy about this whole ordeal, but it was a
g</SPAN></SPAN></FONT><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>ood
thing </SPAN></SPAN></FONT><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>we caught it with the
megger before we put the power to it.</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>That wire nut became the
first exhibit in what became my collection of training materials for the "what
can go wrong and why we do these procedures" trainings. Verification that
cover and mounting screws cannot come in contact with energized equipment
was officially put in the checklist. <STRONG><U>All</U> </STRONG>cover &
mounting screws in <STRONG><U>all</U></STRONG> types of enclosures. There
would be no exceptions. There would be no excuses. I actually had to write one
guy up for a violation of this at one point. Good thing we caught that one with
the megger before putting the power to it.</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>I would posit that
at least one of the recent PV fires would <STRONG><U>absolutely have been
prevented</U></STRONG> if the installer followed the procedure described above.
</SPAN></SPAN></FONT><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>Too bad most don't.
Kudos to those of you who do. It's only a matter of time until more and more of
these AVOIDABLE problems surface.</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>If you don't have a
megger, get one. If you have one, use it! </SPAN></SPAN></FONT><FONT face=Arial
color=#0000ff size=2><SPAN class=937552300-28042009><SPAN
class=937552300-28042009>The Fluke 1520 is a nice unit. I recommend it over
analog models. I cut my teeth with analog gear, but really like my 1520. A lot!
Rugged instrument that </SPAN></SPAN></FONT><FONT face=Arial color=#0000ff
size=2><SPAN class=937552300-28042009><SPAN class=937552300-28042009>gives you
an actual number to write on your commissioning sheet. In addition to Megohms,
it also does VAC, Lo Ohms, Continuity, has a display backlight, Lock and Zero
functions and my favorite.... Battery Check! Reads out an actual % value
for your battery condition. Nice! </SPAN></SPAN></FONT><FONT face=Arial
color=#0000ff size=2><SPAN class=937552300-28042009><SPAN
class=937552300-28042009>Uses 4 "C" cells.</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>I hope more hands go up
on this topic. Thanks for asking, Keith.</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>Peace and Palm Trees
everybody,</SPAN></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN
class=937552300-28042009></SPAN></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=937552300-28042009><SPAN class=937552300-28042009>Matt
Lafferty</SPAN></SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2></FONT> </DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <B>On Behalf Of </B>Keith
Cronin<BR><B>Sent:</B> Monday, April 27, 2009 2:37 PM<BR><B>To:</B>
RE-Wrenches<BR><B>Subject:</B> [RE-wrenches] To Megger or not to
Megger<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman,new york,times,serif">
<DIV>Hi<BR><BR>I was wondering, by a show of hands, how many of you megger every
project?<BR><BR>Do you have a cut off- like if it is "x" sized system, you will
or decide to opt out of performing this task?<BR></DIV></DIV><BR></BODY></HTML>