Grounded for two weeks...hopefully longer [RE-wrenches]

[Geoff Greenfield]

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I agree that this is an area of big potential improvement...

We currently use stranded bare #10 with crimp lugs and "green" screws to
bond all panel frames, rack and poles, with #6 solid and tinned mechanical
lugs where we are "subject to abuse"...  My personal array has 7 years with
the crimp lugs starting to rust but still good mechanical and electrical
connection.  Probably not going to last 30 years!

I like the zig zag through SS screws approach that was posted- especially
for flush mount roof jobs - will be trying it!

Here is my question? - On the concept of using racking AS grounding (with
star washer for positive connection) I have heard of large arrays doing this
and passing inspection.  Specifically - BP supplied and installed a 25KW
ground mounted affair that used galvanized steel racks made out of tube
steel posts and a primary E-W strong back, then with unistruts attached to
that and panels attached to that.  No grounding other than the "steel"
racking.

Now, congregation, please open the good book and turn with me to the
grounding 250:verse 136...

And the NEC said ye shall ground the panels... and it was good....


Ok... seriously:

Looking at NEC 250.136 we see exception A for "non-current carrying metal
parts" - "...secured to or in electrical contact with a metal rack or
structure provided for its support and grounded by one of the means in
250.134.  (metal frame of a building doesn't count for AC equipment)"

250.134 then discusses conductors or methods, referencing 250.118.

250.118 is types of grounding conductors - listing wire, but also includes
cable trays and gutters listed for grounding (referencing 392.3C and 397.7)

I am assuming that unistrut and other struts are listed as grounding
conductors and this is how this system passed.  Perhaps in addition to
asking the PV manufacturers to broaden their grounding methods, we should
approach UniRac and the rest and get their products listed as grounding
conductors.  I would rather string a #6 along a large array bolting to every
second unirac rail, or even the steel substructure!  Am I correct that our
answer is already in the Code and we just need to come up with a way to
comply? (like switch to unistruts until the racking companies get with the
program?

Perhaps some comments from Pastor Wiles...?

Sincerely,

Geoff Greenfield
NABCEP Certified Solar PV Installer TM
GLREA Certified Photovoltaic Systems Integrator/Installer License Number
0211-01

THIRD SUN SOLAR AND WIND POWER Ltd.
340 West State Street, Unit 25
Athens, OH 45701

Phone (740) 597-3111
Fax   (740) 597-1548

www.third-sun.com



------------------------------

Date: Wed, 31 Mar 2004 22:23:23 GMT
From: Jeff Oldham <starpower4u at juno.com>
Subject: RE: Grounded for two weeks...hopefully longer [RE-wrenches]




We just finished a 20 kW ground mount and my installer called me to say he
found a "better way to attach the modules, faster and cheaper, come take a
look". Fearing the worse I hustled on over and found that they used #10 SS
drill point screws w/SS washers up through the slotted channel and into the
frame wherever they could hit (no, not the manufacturers intended holes, but
within an inch or so). The first thing I noticed is that we now have a good
electrical connection between the module frame and the strut, bonding all
module frames to the entire structure. It looks like a reasonable direction
to consider as we explore ways to ground zillions of module frames together
on an array. I know we all want to see this get to the point of one ground
point per array. We still bonded all frames with lugs and #10 CU. We all
agree - there just has to be better way than this silliness.

I just got back today from doing a tour for a group of 20 IBEW electricians
and when this issue of frame grounding came up they just could not believe
that our industry has not sorted this out and we have to "do it the hard
way".

Come on manufacturers, help us out here, this cannot be rocket science! It
is pretty bad when it takes longer to ground a module than to mount it.

-jeff o


>From the Solar, Wind and Hydro powered office of Jeff Oldham

End of RE-wrenches at topica.com digest, issue 1413


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