[RE-wrenches] Wire Management--was RE: Rooftop wiring

[Max Balchowsky]

You're right Bill, It's not and the best method is to have a uninterrupted bare copper in layin lugs at each rail then into the j-box. We always check the ground to see what we have as far as resistance. We built a lot of high rise electrical projects during the 80's and early 90's. Every now and then I walk some of those jobs - lots of power strut and strut clamps or Mini's, but I never see much corrosion, even after all these years exposed on the roof.




________________________________
From: Bill Brooks <billbrooks7 at yahoo.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Wednesday, October 14, 2009 4:07:18 PM
Subject: [RE-wrenches] Wire Management--was RE:  Rooftop wiring

  
Max,
 
Is the Minerallac clamp really rated as a bonding device? I don’t
think so. It may make an electrical connection, but I don’t think it is nearly
as good as a ground bushing. It is also made of cad-plated steel and I don’t think
it is as durable as EMT or a ground bushing with a cad plated fastener. It
probably doesn’t matter too much if it is just protecting conductors and a
bonding conductor between two rails, but I would not want to rely on this for
any circuits containing the final equipment grounding conductor or main circuit
conductors. Not something I would lose a whole lot of sleep over—there are far
bigger issues to solve. Of far more significance is the overall wire management
of USE-2 conductors in the array. Structure suppliers still do a terrible job
of providing an effective means of controlling and protecting conductors—this is
nearly a decade after the first commercially available system was developed. Is
anyone else ticked off about this???
 
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: Wednesday, October 14, 2009 2:59 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Rooftop wiring methods between multiple
subarrays
 
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.
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