Electrolysis Damage Story [RE-wrenches]

[Darryl Thayer]

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Hello
I reject the basic premise. I have seen similar
events, many times, both on electrical posts and non
electrical posts.  I have seen many mailbox support
posts rust off at the bottom.  If water can enter the
post the rusting is faster.  If the soil is acidic the
corrosion is much faster.  Further I am puzzled as to
how voltage was determined at the pole. (what was it
measured from?) I think if you drive a copper ground
rod and a Galvanized pole you have a electrolysis
potential.  If it rains, the water splashes against
the pole and stays moist at the bottom longer than
anywhere else.  The moisture splashed water and soil
are the sources of the corrosion.  Some inspectors in
my area would require the concrete extend above the
ground and taper away from the pole.  

I always ground the array frame, and the pole, and
include a ground conductor back to the ground at the
house.  A GFDI is not required in this case, and I
would have 'if the inverter allowed' grounded one of
the PV conductors at the house (at a single point). By
using a ground on one of the PV conductors the loss of
performance should have been easily detectable.

If you had a high voltage inverter it would have had a
GFDI installed.   
Thanks Darryl
Others please respond if you have rusting at the
bottom of the pole and how to control.

--- Allan Sindelar <allan at positiveenergysolar.com>
wrote:
> Wrenches,
> A simple mistake can have major consequences.
> 
> In 1997, in my first year of business, I designed
> and sold a SW4024-based
> grid-tied system for a new home. As I wasn't
> licensed at the time, another
> local electrical contractor with a history of doing
> solar installations was
> separately contracted to pull the permit and do the
> installation. Upon
> completion, I corrected a few things I didn't like
> (battery cables connected
> at one end of the bank, rather than diagonally, for
> example) and have
> supported the system and the customer in the years
> since. This is a good
> customer.
> 
> The system has worked well, with only the Wattsun
> tracker and the E-Meter
> requiring repair or replacement. The client called
> recently about tracker
> malfunction, and today Mark (partner) went to the
> site to service it. What
> he found was battery voltage at the tracker ground,
> which he determined was
> from a ground fault at the array. The galvanic
> action caused by the fault
> had rusted the 8-year-old 6" Sch 40 steel pole to
> the point that he could
> poke a screwdriver through the pole at the base, and
> was concerned about the
> whole thing toppling over any minute.
> 
> The cause of the ground fault was the use of two
> 1/2" Romex clamps for
> strain relief where the USE-2 array input conductors
> entered a steel 3R
> combiner box on the pole. Each of the two clamps
> held four #10 USE-2
> conductors and one bare #8 or #10 grounding
> electrode conductor. One of the
> clamps had shorted one of the PV+ conductors to
> ground. I am guessing that
> it had been like this for a long time, maybe since
> installation, and I had
> never detected the fault during routine service
> calls. An array GFDI wasn't
> installed or required (and I'm not sure anyone even
> made one at that time).
> 
> The customer is looking at repair options for the
> pole, including outriggers
> with driven steel posts and welded braces, and a
> poured concrete cap over
> the base of the pole. We will head out soon to
> disassemble the array, to
> reduce wind sail and the chance that it will come
> down, and to buy some time
>  for a good repair to be devised. We are also
> looking at setting a 5" steel
> pole inside the 6", with cement slurry between the
> two.
> 
> We haven't worked out a course of action yet. A
> couple of questions:
> 
> We use SO connectors for USE wire, and use Romex
> clamps for jacketed wire in
> indoor locations. Is the use of Romex clamps on USE
> wire in this application
> legal per NEC? What Code section addresses this?
> If issues of liability and responsibility come up
> (and they probably will
> not) who's liable? The contractor who installed the
> system and pulled the
> permit? The inspector who signed off on the job? Us?
> How would you serve the
> customer in this case? I supplied a one-year
> warranty on system design and
> component failures, and the installer gave the same
> against failures due to
> incorrect installation.
> 
> Has anyone ever repaired a rusted pole? Howdja doit,
> and did it work?
> 
> Thanks for any good advice. I'll share your
> responses with the client.
> 
> Allan at Positive Energy
> 



		
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