DC-GFP/2 protection [RE-wrenches]

[Joel Davidson]

Bob-O, Thanks. In case you all have not noticed a pattern in wrench practice,
I'll spell it out for you. All experienced wrenches in lightning territory prefer
to float the DC. Some wrenches only ground the DC when forced to do so. All wise
wrenches earth-ground equipment like their livelihood depends on it.

"Bob-O Schultze, Electron Connection" wrote:

> 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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