I second Mike's suggestion for sunglasses on startup. Wait, ........better go
for welding helmets. Those DC arcs are bright. And I bet they didn't use listed
electrical tape either! :-)  Thanks for sharing this one.

Dick Ratico
Solarwind Electric 

--- You wrote:
Typically those types of modules are rated for 30V.  Most 12v amorphous modules
under 40 watts are rated for that.  I would recommend  sunglasses for startup.

 

 

Mike

mike@powerupco.com

 

From: re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] On Behalf Of Jeff Yago
Sent: Tuesday, April 27, 2010 9:04 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] low voltage modules in high voltage applications

 

First let me say that we almost never work on failed systems, especially when
its for somebody that picked our brains on pretense of buying a system, then
they went out and bought everything on the internet, and when nothing worked
they call us!

Also, let me say that the following project has nothing to do with us other than
a call from an electrician who is installing a grid-tie system for somebody I
don't know who had a few general install questions and was hoping I would
provide some guidance.  My advice was to run as fast as he can!   Here is the
story-

This commercial building owner went to Harbor Freight and purchased a trailer
truck load of 12 watt battery charging modules.  You know the ones you see
advertised to trickle charge a car or boat battery.  I have not actually seen
the modules this guy purchased, but based on others I have seen they typically
have a potted junction on the back with 3 feet of very limited insulation wire
pair out with bare wire ends.  A few more questions and answers indicated these
were made in China, had no label listing their ratings except indicating 12 watt
at 14 volts.  The very large physical dimensions he gave for such a small
wattage tells me they are those thin frame amorphous you see being sold to keep
your truck or tractor battery charged.

To make a long story short, this electrician said they had already mounted
"hundreds" of these modules on the roof of a warehouse, and were wiring them in
series for connection to a Fronius grid-tie inverter.  Also, he said the wires
from each module was routed through a separate hole in the roof and then tied
together.  I assume this was by the ol ball of electrical tape wiring method.

Not counting the obvious code related problems with what they are doing, and the
almost sure need to have a fire truck nearby when they start this thing up, does
anybody know what a typical high voltage rating would be for this type of module
and the small wire pair?    My guess is the small wire and/or the modules will
quickly break down and start arcing, then the entire array will melt down which
is what I told this electrician could happen.  However, since there is no label
on the module, I am only going on gut feeling as to the voltage rating of these
cheap modules which I am sure were clearly never designed for series wiring to
achieve high voltage.

Anybody know these ratings?  Should I sell tickets for the fireworks show?

Thanks,

Jeff Yago


 
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