DC-GFP/2 protection [RE-wrenches]

[Bob-O Schultze, Electron Connection]

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Group,
Excellent thread, as grounding is the most misunderstood and 
controversial of all electrical topics.
I do not ground the DC side on 12 or 24V systems. I always plonk in a 
ground rod for lightning at the array (five at a wind tower) which I 
DO NOT tie into the electrical grounding system. I also use lightning 
arrestors on anything coming into the house or power shed. I've had 
nearby strikes turn inverters off a few times, but so far, never a 
fry and die.
Best, Bob-O

>Grounding the negative cable is not required on systems under 50 volts as
>most of us know.
>My conversations with Mick Sagrillo and his articles on lightning protection
>don't recommend grounding the negative. That way you don't give the
>lightning surge a path to ground through the batteries.
>I also put a lot of ground wire in a "net" around the base of the windmill
>towers that I install or rebuild after a strike (not my install) and connect
>it to the main ground system that way everything has the same ground
>potential.
>I too like to hook to the well casings if possible, it's hard to beat a 40'
>ground rod.
>
>Seems like the lightning "pulse" is more common damage than a direct strike.
>Shielded cable seems to help on windmills with exposed cable.
>I know of one 20 year old Bergey with the wire hanging in the tower that has
>never had a lightning problem.
>Come to think of it, there is no inverter, just a rectifier it is a 120 volt
>DC system. Can't hurt an inverter that is not there!
>Lightning control is almost a black art, and sometimes nothing helps.
>
>Just my .02 worth, your opinion will vary.
>Bob
>
>RE. Ellison
>Supplier of;
>Alternative Energy Systems & Supplies
>34642 Countryman Road
>Theresa, NY. USA
>                                13691-2076
>
>
>-----Original Message-----
>From: David Palumbo, Independent Power & Light [mailto:ipl at sover.net]
>Sent: Thursday, August 22, 2002 9:43 PM
>To: RE-wrenches at topica.com
>Subject: RE: DC-GFP/2 protection [RE-wrenches]
>
>
>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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