Module grounding [RE-wrenches]

[William Miller]

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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William Miller
Miller Power and Communications
PO Box 50, Santa Margarita, CA 93453
Voice :805-438-5600		Fax: 805-438-4607	VMail: 805-546-4875
email: wrmiller at slonet.org
http://millerpowerandcomm.com
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