Ray,
Conductors can be mislabled regardless of the system used. The accident you
described had nothing to do with conductor color or labeling. It was caused by a
gross violation of sound electrical procedure and plain common sense. Your
electricians failed to check for correct polarity before making their
terminations.

I grant your system works for you and could for others. But until the NEC forces
us all onto the same page, an argument can be made that any coding system is as
confusing as another. Pardon the pun, it depends on the way a wrenches's head is
wired. 

Dick Ratico
Solarwind Electric


--- You wrote:
We have standardized on DC markings White negative and Red positive.

Chris Mason
Comet Systems
Anguilla (264) 235-5670
St. Kitts  (869) 662-5670
skype netconcepts

NABCEP Certified Solar PV InstallerTM
Renewable Energy Systems professional
Generac Generators Factory technician
On Jun 29, 2013 8:30 PM, "David Katz" <dkatz@aeesolar.com> wrote:

> Watch out for accountants who become installers.  They always thing red
> negative and black positive.
> David Katz
>
> Sent from my iPhone
>
> On Jun 28, 2013, at 5:40 PM, "Ray Walters" <ray@solarray.com> wrote:
>
> > Richard, when you use your Fluke 87  to measure Vdc, black is negative,
> > red is positive.  The black is labeled common because the meter can also
> > be used for current measurements. (I have a Fluke 89)
> > When you start using black wire for positive, it may be allowed by code,
> > but there just isn't a good reason for it.
> > Its just too easy to make a mistake, and its just too easy to adhere to
> > the multimeter convention and keep it safer.
> >
> > I have personally watched seasoned electricians argue color coding with
> > me, then minutes later get mixed up and wire two 10 module strings in
> > series, because they forgot for a moment that they were working on a
> > positive grounded system.  The result was an almost 1000 v arc that
> > jumped an opened fuse holder (only rated to 600 vdc) and started a small
> > fire in the inverter, before I disconnected it at the array.
> >
> > Please give one example where leaving positive unmarked with black wire
> > makes more sense than taping it.  Colored electrical tape, and label
> > tape are much cheaper than inverters and people.  THHN, USE, and PV wire
> > can all be purchased in red, white, and black. (which saves time with
> > multiple  home runs)
> > Its not code yet, but it's good sense, all the way back to the color
> > coded jumper cables you might have in your trunk.
> > I have discussed this with many electricians over the years, but
> > eventually every single one sees that's its really easy, no cost, and
> > still code compliant to make things safer.
> >
> > R.Ray Walters
> > CTO, Solarray, Inc
> > Nabcep Certified PV Installer,
> > Licensed Master Electrician
> > Solar Design Engineer
> > 303 505-8760
> >
> > On 6/28/2013 2:49 PM, Richard L Ratico wrote:
> >> Respectfully:
> >> My Fluke 87 does not use this convention. Black is labeled the COMMON
> terminal,
> >> the red terminal is labeled according to function, not polarity.
> Battery based
> >> inverter manus. using this convention typically provide BOS enclosures
> with OCP
> >> for only one inverter conductor. This requires the other conductor to be
> >> grounded and colored white or gray. Therefore IMHO the manus. should
> use only +
> >> or - to identify inverter terminals. Many, if not most, battery
> companies do
> >> this already. Mr. Wiles is, of course, welcome to his opinion.
> >>
> >> I would suggest we stay with the NEC required use of any color other
> than white,
> >> green or gray for ungrounded conductors. This gives installers some
> flexibility.
> >> It also encourages the guy on the hot roof or the gal in the stuffy
> mechanical
> >> room to check and double check, maybe triple check polarity, as they
> should be
> >> doing anyway. I do like the practice of enhanced identification of
> conductors in
> >> positive ground systems.
> >>
> >> Dick Ratico
> >> Solarwind Electric
> >>
> >>
> >> --- You wrote:
> >> The convention of red for positive and black for negative is not just
> >> automotive.  It is also used by all battery based inverter manus, all
> >> battery companies, and all multimeters.
> >> John Wiles also agrees;
> >> red = positive, black = negative  for ungrounded systems
> >> red = positive, white = negative for negative grounded systems
> >> white = positive, black = negative for pos grounded systems.
> >> I take it a step further, and use white label tape with red lettering
> >> that says "+ positive ground + ",
> >> because I've seen so many problems with positive grounded systems, and
> >> people not getting polarity correct.
> >> All of this is NEC compliant, and follows standard conventions.
> >> Make it easy on yourself and your journeymen on a hot roof, and have
> >> your color coding match their multimeter.
> >> You might save an inverter or even a life.
> >>
> >> R.Ray Walters
> >> CTO, Solarray, Inc
> >> Nabcep Certified PV Installer,
> >> Licensed Master Electrician
> >> Solar Design Engineer
> >> 303 505-8760
> >>
> >> On 6/28/2013 12:09 PM, Allan Sindelar wrote:
> >>> On 6/28/2013 11:47 AM, aram@aramsolar.com wrote:
> >>>> And of course Red for positive and black for negative.
> >>>> Most building departments have not pick up on this yet. But they will.
> >>>> Aram
> >>> Where does "of course Red for positive and black for negative" come
> >>> from, please? I only know it as an automotive standard that has often
> >>> caused confusion when used by DIY offgridders in years past, as black
> >>> thus could represent either positive or negative in a DC conductor
> pair.
> >>> Is there yet a convention for ungrounded arrays? While red and black
> >>> are technically correct as ungrounded current-carrying conductors, use
> >>> of this color convention could cause as much confusion as resolve it
> >>> in the future. How about "black and black" or for that matter "yellow
> >>> and orange" (if supplied by manufacturers) for ungrounded arrays?
> >>> Thanks, Allan
> >>>
> >>> *Allan Sindelar*
> >>> _Allan@positiveenergysolar.com_ <mailto:Allan@positiveenergysolar.com>
> >>> NABCEP Certified PV Installation Professional
> >>> NABCEP Certified Technical Sales Professional
> >>> New Mexico EE98J Journeyman Electrician
> >>> Founder and Chief Technology Officer
> >>> *Positive Energy, Inc.*, a Certified B Corporation^TM
> >>> 3209 Richards Lane
> >>> Santa Fe, New Mexico 87507
> >>> *505 424-1112 office 780-2738 cell*
> >>> _www.positiveenergysolar.com_ <http://www.positiveenergysolar.com/>
> >> --- end of quote ---
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