rooftop wiring/grounding [RE-wrenches]

[Jeffrey Wolfe, Global Resources]

Nothing against conduit William, we sometimes use it, and it does result in 
a nice project. BUT, we're trying to reduce the cost of our installations 
(while maintaining quality and longevity) and a lot of the modules are now 
coming with a potted box and two multi-contact leads coming out - no place 
to attach conduit to.

In moving toward the wire tray, I think we'll provide the protection of 
conduit (wire wil be USE-2), we'll avoid the higher temps in the conduits, 
and we'll be faster using the plug and play approach.

Jeff

On Saturday, April 13, 2002 12:22 PM, William Miller 
[SMTP:wrmiller at slonet.org] wrote:
> Colleagues:
>
> Why are so many installers against the use of conduit?  I really like 
using
> 1/2" non metal liquid tight to interconnect modules.  At each rack, I
> connect to a PVC J-box and transition to schedule 40 PVC.  Here are my
> reasons for using conduit:
>
> -I know there is a hair splitting compliance question regarding 
temperature
> when using non-metal flex, but I've never seen the flex fail or degrade.
> -In just about any other commercial/industrial wiring situation, wire is
> protected by conduit.
> -Conduit has many provisions for attaching to supporting structures.  I 
use
> a 1/4" beam clamp attached to a mineralic conduit hanger to attache to 
rack
> rails.  I use a beam clamp to attach PVC J boxes to rack feet and
> transition to PVC.
> -PVC is listed as sunlight resistant.There are many UV resistant coatings
> to protect PVC from discoloration.
> -Non metal liquid tight conduit is water tight.
> -Conduit protects wire from abrasion.
> -Conduit allows one to wire in series, parallel or any combination.
> -Conduit allows one to put more than one wire into a knockout.
> -Conduit can be used to route a ground lead along with the current 
carrying
> conductors.
> -Non-metal flex and schedule 40 PVC is readily available and inexpensive,
> as is THHN stranded.
> -When using conduit, one can change out wiring if there is a failure or
> change in design.
>
>
> William Miller
>
> At 10:45 PM 4/12/02 -0400, you wrote:
> >For wiring both between modules, as well as longer runs to a central
> >combiner box, we are working with the multi-contact cables, made for 
each
> >project for us by Kensington. To keep them in some sort of order, or at
> >least away from abraision, we had been simply tie-wrapping to supports,
> >etc., but I've not really been pleased with it.
> >
> >We are now going to try out some plastic cable tray which we can fasten
> >directly to the horizontal rack supports. This will give us a nice place 
to
> >tuck all wires, let us get at them if we need to, and should proceed
> >faster. At any rate, it keeps the wires out of harms way.
> >
> >At the end of the rack, we'll transition to a piece of flex (through a
> >multi-wire gland connector) unless the combiner box is within inches of 
the
> >end, in which case we would simply let the wires come out the end of the  
> >tray.
> >
> >The idea is to make the roof work fast and easy, and as fool proof as
> >possible. (I can be a pretty good test for that some days....)
> >
> >We'll let you know how it works after we do a few.
> >
> >Jeff
> >Jeffery D. Wolfe, P.E.
> >Global Resource Options, LLP
> >A Woman-Owned Limited Liability Partnership
> >4 Kibling Hill Road
> >P.O. Box 161
> >Strafford, Vermont 05072
> >800-374-4494 Toll Free
> >802-765-4632 Phone
> >802-765-9983 Fax
> >global at sover.net
> >http://www.GlobalResourceOptions.com
> >
> >Nextek Certified Distributor
> >SolarWall Certified Distributor
> >Trace Certified Dealer - Charter Member
> >Bergey Windpower Certified Dealer
> >
> >
> >On Friday, April 12, 2002 12:31 AM, Brad Bassett
> >[SMTP:bsbassett at earthlink.net] wrote:
> >> First, I would like to say that I had no intention of denigrating all
> >> California solar installers. Now that I've seen the responses, I 
assume
> >> that unprotected home run wiring is not the norm anywhere. That there
> >> are installers that do better work than others will always be true.
> >>
> >> My comment about Washington inspectors has mainly to do with the fact
> >> that outside of the cities, the inspection is done by a state agency,
> >> and they tend to be consistant sticklers. That's OK if you do it right
> >> (and can quote chapter), and have UL listed equipment (no UL = no
> >> acceptance).
> >>
> >> I agree that the wiring between modules is still a concern. I've seen
> >> wires sitting on the roof in many installations, and in the back of my
> >> mind am thinking that an entirely different wiring method needs to be
> >> designed for wiring between modules. The gears are whirring in my 
mind,
> >> maybe someday I'll be able to do something about it. I understand why
> >> some agencies are tending toward conduit used everywhere, but this can
> >> be quite a bit of overhead if done with conduit said to be rated for
> >> that use. And as pointed out, conduit can be poorly installed also. 
This
> >> leads to another question, what are some good methods for supporting
> >> conduit on a roof? (I will ask this within our company and get some 
more
> >> answers too, I'm sure)
> >>
> >> On the grounding of modules, I'm surprised to hear that grounding of
> >> individual modules is actually done! I figured this was skipped by 
most,
> >> I guess not. I'm used to working with ASE-300's which make it easier,
> >> both because they have a threaded insert in the frame with grounding
> >> hardware, and because there are fewer modules for a given size system.
> >> (Yes, star washers are made to break the anodized or painted surface 
for
> >> electrical continuity)
> >>
> >> Brad Bassett
> >> Schott Applied Power
> >> Tumwater, WA office
> >> bsbassett at earthlink.net
> >>
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> __________________________________________________________________
> William Miller
> Miller Power and Communications
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