Connections and Understanding [RE-wrenches]

[Matt Lafferty]

Wrenches:

Sorry for the last one....accidentally hit Send before typing... (Bad PvPro!
Bad PvPro!)

While I prefer beer to wine (He lives closer to the Napa Valley than I
do...), I share Bill's concerns.

It is not specifically directed toward the MC-Paralell Branch connector, but
the very real possibility for misapplications in it's use.  This is not the
fault of Multi-Contact.  The same situation (leaving the string unprotected
by fuses) can and does occur with other methods of paralelling source
circuits.  It arises due to misunderstanding of series and paralell
circuits, overcurrent protection and its purpose, our glass as well as PV in
general.

When training installers, I demonstrate over and over the "on-paper"
relationships of series and paralell circuits as well as "hands-on".  It is
interesting watching them confuse one for the other on paper and thinking
"Oh, well.  No big deal. It was just a math error", then going out to the
array and actually doing it.  That is when it sinks in, especially on a
sunny day.  I make them "accidentally" mis-connect between strings to see
it.  Yes, it is math.  But it is math that is so very important.

I have found that it is one thing to measure the volts and amps on your
Fluke but, quite another to "light 'em up" after you have taken the
measurements.  The size of the arcs in relationship to the meter readings
starts to sink in.  The key is that this is all Watts, not just Volts and
Amps.  It doesn't matter whether it's a 48 or 600 Volt array, it is the same
amount of Watts and it will make fire if you don't do it right.  Where are
you in the overall circuit?  Where is the Power coming from?  Where is it
going?  Are you properly protected?  Are these two wires hot right now?
Ouch!  Dammit!

The real "sinker-in" is when putting two 480 VDC strings in series,
measuring it, hearing them say, "Ooooh.  That's cool", then having a
competition to see who can draw the longest / best arc.  It is after this
portion of my classes that they take this stuff seriously.  There's
something about realizing for the first time that the Sun is really making
electricity and the only thing there is to shut it off is the rotation of
the Earth.

Respect, my friends.  Respect Mother Nature.  Respect Her Power (Watts, in
this case).  Respect what it is that you are doing.

You may understand these principles, but do the guys that work for you?
What kind of quality control safety procedures do you have in place?  Do you
measure your voltages and currents before energizing your equipment?  Every
single time?  Do you use a pyranometer and thermometer?  Do you do the math
to see if the array is doing what it is supposed to?  If you aren't doing
these things, you aren't being responsible.  The math is simple and it takes
just a minute.  It is interesting to me when I "bust" somebody on this.
There is no excuse (if you are working for me, THERE ARE NO EXCUSES!)  The
numbers tell all.  I can tell from the numbers and where the sun is, what
they did wrong.

We all make mistakes.  The most dangerous mistake is thinking we "know all
that" then becoming complacent about checking ourselves.  We as humans are
often quick to criticize others but not apply that same outlook to
ourselves.  "I've done this a thousand times" is one of the most dangerous
mentalities I can think of.

Moving forward....As our industry grows (growth means change, by definition)
there will be new products & methods, new installers, new Codes & Standards,
etc.  Some will be good.  Some will be bad.  Some will be Very Bad!

It is our responsibility as individuals to ensure that we monitor and report
the good and the bad.  That we continue to learn.  Continue to grow.  Ask
questions when you aren't sure.  I do, every time.  (Regardless of what Bill
B says, not even he knows it all.)  :-)  That we share our experiences on
both sides.  That is why this list exists and what, I believe, we all expect
from it.  Ask.

I am glad, for instance, that the MC Paralell Connector thread got
started....and the various Lightning threads....and the Paralell Brain
Teaser....and....and.....

It was because somebody cared enough to ask.  We have a long way to go
before we can say "We've won!".  We've come a long way, though, and in
general are headed in the right directions on many fronts.  Don't quit now!

Pray for Sun!

-Matt Lafferty
pvpro at attbi.com


> From: "Bill Brooks"

> I find that a smooth glass of wine works well when trying to ponder the
> stranger things in PV. Just a little clarification for those who might
have
> misinterpreted my statements as having come on strong with the MC issue.
The
> problem is not the MC connector, nor is it the idea of developing a
> paralleling cable to assist in wiring an array. The problem as I see it is
> the possibility of some misapplying the connector in the field and trying
to
> parallel multiple strings of crystalline modules into a battery-based or
> some inverter that could be a source of backfed current. Currently no
> crystalline module on the market can handle that situation.
>
> I can think of the one case in my Brain Teaser message where a harness
that
> could combine two or three strings together would be a good idea. However,
I
> know that I would spend the next three years of my life training
installers
> to only use this connector when connecting SP75 modules to a SunnyBoy
system
> and don't do it when connecting them to a Xantrex Sun-Tie, or whatever.
>
> It complicates life for the installer/designer which is why I'm so stuck
on
> fully engineered system packages. We are starting to hear stories about
> installers connecting 1000 Volts to SunnyBoys by accident, finding all
kinds
> of new ways to connect 600 volts improperly, and it scares the heck out of
> me. I think there is far too little manufacturer's training on this
> equipment and far too few engineered system packages.
>
> I know most of the wrenches design their own systems, but how do people
feel
> about the newbees designing systems? How about wrenches with 600 Volts--we
> talked about this over a year ago on the list and there was a lot of
> well-deserved apprehension--I'm still worried.
>
> Bill.

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