[RE-wrenches] Rooftop wiring methods between multiple subarrays

[Bill Brooks]

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? <http://minerallac.thomasnet.com/viewitems/pipe-fasteners/ll-categories-cully-pipe-fasteners-conduit-hangers?&bc=100%7C1006%7C1281&forward=1> &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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