Asian & European Installers [RE-wrenches]

Tue May 28 09:46:19 PDT 2002

To get an answer to these questions, check out the latest issue of
Photon magazine.  In this issue you'll find that across Europe (there's
no mention of the Japan market) integrators are running into the same
kind of problems that we have only it's often even worse over there.  In
places like France, Germany, Spain, Italy and Portugal, utilities are
making the PV industry go through the same kind of hoops as we go
through here.

marco
proVision technologies, inc.
hilo, hawai'i
www.provisiontechnologies.com

Do you have clear and concise regulations to intertie with the utility?

Do you have to deal with lack of clarity & communication between the
utility
and the RE installing businesses?

Do your governments encourage or discourage grid intertie?

Do you have nation wide incentives designed to encourage renewable
technologies?

Do you have clear and non-contradictory equipment testing methods
designed
to work the glitches out before the equipment goes to market?

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From: Bill Brooks <billb at endecon.com>
Subject: RE: Parallel Danger? [RE-wrenches]
Date: Tue, 28 May 2002 10:04:29 -0700
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Ray,

I really don't want to get into comparitive danger discussions (or parallel
universe discussions) because I'm not sure what they accomplish and they
rarely hold water with the powers that be.

Bottom line is that UL tests a PV module with a given amount of current
flowing through it--nothing more. Whether that module can handle twice the
current or spontaneously combusts at 135% of that rating is totally
irrelevant. The UL listing is what is at stake. The point is that if you
provide for more than 15-amps to a 15-amp module (two SP-75s in parallel
plus a 15-amp fuse), you have violated the UL listing and cannot install it
in a code-approved manner. If the system does cause a fire, UL could be
obsolved of all liability because you installed a listed product
improperly--even if the modules had nothing to do with it.

As to whether systems in developing countries should meet our code--my
response is that it should meet the spirit of our code, if not the letter. I
have designed and built many systems overseas and I try to stay very close
to our code and use listed equipment because it gives predictable results
and will last a whole lot longer than other stuff. A huge percentage of
systems in developing countries are sitting off-line doing nothing, or have
been rigged to run in an unsafe way because products failed and were not
designed properly. What is the difference in cost between a system that
lasts one-year and one that lasts 10 or 20 years. Is it worth an extra 20%
in cost to last 10 times longer (last I checked the economic answer was
yes). Overcurrent protection, disconnects, proper wire, proper mounting, are
all part of performance, reliability, and maintainability. It is very
difficult to divide the issues and truly cut costs. (but people do it all
the time with bismal results)

Bill.

-----Original Message-----
From: Ray Walters [mailto:remotech at taosnm.com]
Sent: Sunday, May 26, 2002 4:33 AM
To: RE-wrenches at topica.com
Subject: Parallel Danger? [RE-wrenches]

Hi Bill and all;

Here is another potentially dangerous situation to ponder: a 5amp UL listed
device (a computer) is powered through 16 awg SJO cord to a 15 amp rated
receptacle. This receptacle is PARALLELED with several other 15 amp rated
receptacles (35cents made in China). This whole circuit is fed through a 20
amp breaker. Coffee spills on the computer creating a short. Because of the
time/ current performance of the breaker, over a hundred amps could pour
into our soaked device for a few seconds and  20 amps could flow
continuously into a device UL listed for only 5.
Compare this scenario, with my maligned array wiring method: two array
strings each having a short circuit output of 4.75 amps and a series fuse
rating of 15 amps feed thru 12 awg wire  in parallel for a total of 9.5
amps to a 15 amp breaker. A moose chews through the wire creating a short.
Up to 15 amps continuous are allowed to backfeed into the circuit ( the
charge controller also failed) and are boosted another 4.75 amps by the
paralleled string. This time almost 20 amps could possibly (but not
probably because of the high resistance) flow into a device UL listed for
only 15.
Why is the first condition allowed, but the second is not? Is 120 vac safer
than 48 vdc?

Sincerely again,

Ray

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