DC-GFP/2 protection [RE-wrenches]

Joel Davidson joeldavidson at earthlink.net
Thu Aug 22 20:53:46 PDT 2002


Jacobs use to float the DC negative on his wind machines to prevent lightning
damage. He grounded the tower with a ring of copper wire 10 feet out from the
tower base buried about 18 inches to form a cone of protection. I resisted
(pun?) grounding the DC negative for years, but finally gave up. However, my
systems are almost all in regions with low lightning danger. What say you guys
in lightning territory?

"David Palumbo, Independent Power & Light" wrote:

> Jeff,
>
> Wow! What a timely message for me to see. I have always gone by the book and
> bonded DC negative to ground at one point in the system and have experienced
> no more than the occasional lightning issues.
>
> However I have been recently considering a change to a floating DC system. A
> tech at one of my distributors had my ear on this issue and he was convinced
> that floating the DC negative would help with lightning protection. He also
> said that there was some sort of movement to do away with the language in
> the code that mandates the DC negative bond to ground.
>
> Dave Palumbo
> IP&L
>
> -----Original Message-----
> From: Jeff Yago [mailto:jryago at earthlink.net]
> Sent: Thursday, August 22, 2002 9:12 PM
> To: RE-wrenches at topica.com
> Subject: RE: DC-GFP/2 protection [RE-wrenches]
>
> We just returned from inspecting a brand new 4 month old system (that we did
> not install!!) that had BOTH SW5548 Trace inverters "fried" by lightning.
> This was a 4800 watt totally off grid system.  The AC side of the inverters
> supply a standard 120/240 volt house panel that was grounded properly.  The
> ground mounted array frame was grounded properly also.  However, the
> negative of the DC side of the inverter, batteries, and charge controllers
> were not grounded.
>
> The lightning was "nearby" but was not a direct strike.  Since there was no
> grid connection, the surge could not have entered the AC side.  I for one
> like grounding the DC side and wish this installer had done so also.
>
> Jeff Yago
>
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