[RE-wrenches] Rooftop wiring methods between multiple subarrays

Wed Oct 14 14:59:27 PDT 2009

Bill, as you know, if the array is on a tilted roof (tile track bkts or fast jacks) and the array is monolithic, all the wires go directly from under the panels to the junction box ( I mis-spoke when I said Combiner box, I too don't see the need for combiner boxes on residential systems ).We go directly from the weeb ground lug into the junction box then down. The panels are bonded to the rails with the  Weeb Bonding Clips.  If the array consists of tilted rows, we've used either a bare copper wire tie wrapped to the EMT between rows or run in the EMT (most rows are 18-24" apart depending on angle). What I've done on the last couple of tilted row residential jobs is used the mineralac clamps and EMT between rows (inspector has bought it as a "bond" between rows then used the ground lug on the last row to take the ground into the junction box and down..........

Max

________________________________
From: Bill Brooks <billbrooks7 at yahoo.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Tuesday, October 13, 2009 7:59:13 AM
Subject: Re: [RE-wrenches] Rooftop wiring methods between multiple subarrays

Max,

I’m not sure I understand your scenario completely. The
WEEB-Lug, superior to the ILSCO product, is intended for grounding the rack to
the equipment grounding conductor. Each rail gets a WEEB-Lug and an EGC ties all
those rails together and takes the ground to the j-box to enter the conduit
system (don’t like combiner boxes on residential rooftops). The key is how to
effectively bond metal conduit. Bonding bushings or box fittings are the only
means I know of to do this. As others have pointed out, the bushings currently
on the market are often not designed for outdoor use. This is particularly of
concern in high corrosion areas (where EMT is not recommended). 

My experience is that it is better to bond with indoor lugs than
not to bond at all. When I check old lugs in the field with cad-plated set
screws, they often still have a good bond even though the screw is fully
rusted. The key is the bond between the conductor and the lug, and the between
the lug and the metal it is attached to. If both surfaces are tight and no
oxygen is getting to the interfaces, the bond will stay for a very long time—possibly
the life of the system in a lower corrosion environment. The set screw is
mechanical pressure, not the bonding point—rust  locks it..  It is best to use
outdoor-rated equipment, but in some cases, it may be impossible because the
equipment may not be manufactured, since the market is too small. Oh the joys
of exterior wiring.

Bill.

From:re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Max
Balchowsky
Sent: Monday, October 12, 2009 6:05 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Rooftop wiring methods between multiple
subarrays

Bill, what about using the weeb
bonding method for the panels, conduit between sub arrays with mineralac clamps
and then the weeb grounding lug for 
the ground wire to the combiner box and then home to the panel. The only time
this has been an issue is where the jurisdiction doesn't accept the Wiley
product.....
(I never liked what the sun does to PVC conduit)

Max
Balchowsky
SEE Systems
760-403-6810 

________________________________

From:Bill Brooks
<billbrooks7 at yahoo.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Friday, October 9, 2009 10:20:19 AM
Subject: Re: [RE-wrenches] Rooftop wiring methods between multiple
subarrays

August and Max,

If all you are doing in supporting the conductors, PVC conduit
is sufficient with protective bushings on each end. Once you go to EMT, then grounding
bushings must be installed at both ends and the EGC needs to pick up those
bushings. More expensive and time consuming, but it looks better and you can
span a greater distance. 

Bill.

From:re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Max Balchowsky
Sent: Thursday, October 08, 2009 8:29 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Rooftop wiring methods between multiple
subarrays

August - we've been using 1/2"
emt between arrays with plastic bushings to protect wires and a dual
"minerallac" clamps ( http://minerallac.thomasnet.com/viewitems/pipe-fasteners/ll-categories-cully-pipe-fasteners-conduit-hangers?&bc=100%7C1006%7C1281&forward=1)
to tie the conduits to the riser on the array support. Has worked well over the
years and the inspectors like the "bond" between the arrays.....

________________________________

From:August Goers <august at luminalt.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Thursday, October 8, 2009 11:07:08 AM
Subject: [RE-wrenches] Rooftop wiring methods between multiple subarrays

Hi Wrenches,

I’m looking for fresh ideas on how to run USE-2 wires between
subarrays on rooftops. Let’s say we have a flat roof commercial system with
dozens of separate rows of modules. How would you folks run the USE-2 wiring
between these arrays? We’ve been using J-boxes and EMT which is robust but time
consuming. I’ve also used strut with a cap strip on the top which effectively
makes a wire raceway but it is difficult to properly ground both ends of the
raceway and is also time consuming. 

Looking forward to hearing your ideas. Best, August 

August Goers

Luminalt Energy Corporation
O: 415.564.7652
M: 415.559.1525
F: 650.244.9167
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