Module grounding [RE-wrenches]

Ray Walters remotech at taosnm.com
Fri Jun 7 10:47:43 PDT 2002 

Hi, 

I look at the frame rail material. If it is aluminum and the module frame
is aluminum, I use some star washers between the module and frame and
figure its bonded to the rail. If the rail is painted or otherwise a
different material than the module frame, we bond to each module
seperately. Also, I started using braided plated grounding strap to tie the
rails to a grounding lug Tek screwed into the pole below the head assembly.
I noticed corrosion from apparent galvanic reactions when I used regular
copper to bond to aluminum. SS washers helped, but not much. The plating on
the braid corrodes slightly too, but it appears to hold up the best.
Regular bare stranded or solid copper ground wire #6 then goes from the lug
on the pole to the ground rod. 

Ray

At 10:38 PM 6/6/02 -0700, you wrote:
>Graham:
>
>We prefer the DPW low profile or two tier rack.  We order these in the
>configuration where the modules do not overhang the bottom rail so the
>racks can be tilted up, regardless of whether they will remain tilted up or
>will lay flat.  The racks are left in an elevated position until we
>complete module mounting, grounding, wiring and testing.
>
>We have a crew of three.  One unboxes modules in the trailer and brings
>them to the roof edge.  If the roof is more than 1.0 story tall, we erect a
>short scaffolding.  The ground person hands the module to the roof handler.
> He carries it to the rack.  The third person is under the rack with pre
>assembled bolt packages, the bolt, washer and nut loosely assembled.  The
>carrier holds the module on the rack until two screws are finger tight.
>This proceeds rapidly until all modules are installed.  All bolts are
>tightened with a Makita driver set to the proper torque.  This is very
>quick and efficient and avoids any shop time for pre-assembly.  If you want
>to volunteer a day, I'll call you a few days before our next stack.  This
>will not be for a few weeks, most of us in the crew are going camping!
>
>We use 12 solid green to make a continuous bonding  jumper across the backs
>of the panels.  We toss the factory included grounding screws and use
>instead standard 10/32 green, self tapping grounding screws into the
>pre-drilled holes in the Siemens (Shell) module frames.  The fit is
>perfect. We strip the insulation at each screw with a T stripper and razor
>knife and bend a little omega shape to go under the screw.
>
>We penetrate the roof with 3/4" or 1" PVC.  We LB to a 442PVC J box beam
>clamped to the nearest foot bracket.  We punch the top side for 1/2" and
>feed up to the nearest J box with 1/2" MNLT.  We feed module J box to J box
>with NMLT.  This way we protect all wiring and we can run multiple
>conductors for series and parallel strings.  All parallel connections are
>done in a combiner, either custom fabricated or stock, such as the Connect
>Energy.  We mount one PVC 442 J box per each rack and inter connect with
>3/4 PVC.
>
>We run a 10 or 12 stranded ground conductor from the inverter area to the
>first J box in each rack, and then exit the J box through one of the
>individual wire holes using the neoprene gasket.  We crimp on a ring and
>put the ring under the nearest ground screw, thus tieing the continuous
>sold jumper to the stranded ground "feeder".  We feel this is very direct
>and reliable and is quick to install.
>
>Three of us can set three racks, stack, wire and test 2400 plus watts in
>one day.
>
>For tile roofs, we prefer the DPW standoffs. We have used the Solar Jacks,
>but with only one lag, they do not offer the security we require.  We drop
>two flashings on each standoff before setting racks.  For barrel tile, the
>top flashing is a wide aluminum type.   We leave the racks elevated for one
>night only and work closely with the roofer to ensure they will arrive
>first thing the next morning to tile under the racks.  We come that
>afternoon and lay the racks down.
>
>I threw a few pictures up on my web site just now.  Click on Roof Mounting
>under Downloads.  Hope this information helps.
>
>William Miller
>
>
>
>
>At 04:20 AM 6/7/02 +0000, you wrote:
>>Wrenches,
>>
>>I am trying to figure out the best way to ground each module frame 
>>easily when MC’s are used and the modules are secured with module 
>>clamps?  I am used to panelizing modules into groups of 4 with wiring 
>>and grounding done in shop.  Next we would secure the panels of 4 side 
>>by side on gold galv strut.  Installing modules one by one eliminates a 
>>day in the shop and sounds very quick and easy, but I am still trying to 
>>figure out the easy grounding method.  I know that drilling a hole or 
>>putting a tek screw into a module frame voids warranties but is it 
>>acceptable to take out a module frame screw and replace it with the 
>>grounding-cup-washer that comes with Siemens modules and a slightly 
>>longer stainless steel screw?
>>
>>LADWP had required grounding of each individual module, but I have heard 
>>that just grounding the frame is passable in other municipalities.  I 
>>would rather ground each module.
>>
>>Graham Owen
>>GO Solar Company
>>
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>
>__________________________________________________________________
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>Miller Power and Communications
>PO Box 50, Santa Margarita, CA 93453
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