[RE-wrenches] Cable tray versus RMC

[Carl Adams]

Larry,

We do have the option of no roof penetrations and that is the course
being taken.  We will have 90 source circuits in the array and 5
Jboxes on the roof and these will then be routed to a vertical wall on
the west end of the array.  The strings will carry through the wall
horizontally and then on to the inverters.

My preference would have been to penetrate the roof with RMC and come
directly into the bottom of the NEMA 4X Jbox avoiding the long conduit
runs across the roof ( which will be visible from gorund level).  I
have used the DEKTite
(http://www.itwbuildex.com/gcs_flashings_dektite.shtml)  roof boot for
this type of penetration in the past with good success.  We use the
Eternabond double face adhesive on the bottom of the boot.  WIth the
boot fully under the JBox it will never see the light of day and
should last as long as the array.

The point of my original post was really to find out if the cable tray
approach has been used by other installers for managing the DC source
circuit wiring on rooftops.  Will it meet code?  My understanding is
that cable tray is not classified as a raceway.  It it good practice?
That sort of thing.  I personally would feel better if the source
circuits were in RMC.

Cheers
Carl



On Mon, Feb 14, 2011 at 4:37 PM,  <wirewiz at gmail.com> wrote:
> Carl,
>
> I also have a job on a brand new SS metal roof and I just did not want put any holes in it so I am going down the side of the building and not penetrating at all. But it's only 50kW. Do you have the option of no penetration? I am curious though as to what j-box/sealing/flashing set up you were planning on using.
>
> Larry Liesner
> Wirewiz
> Westport, CT
> Phone: 203-644-2404
> Fax: 203-557-0556
> wirewiz at gmail.com
> www.wire-wiz.com
>
>
>
> On Feb 14, 2011, at 2:56 PM, Carl Adams wrote:
>
>> I have a project for 250kW system.  4/12 pitch standing seem roof  in
>> the Great Lakes snow country.   My initial proposal was to get the
>> source strings through the roof and inside to serviceable combiner
>> locations.  This was shot down by the architect who did not want 5
>> holes punched in his new roof.  So we then shift to pass thru Jboxes
>> where we transition the PV wire to THWN-2 and into RMC back to the
>> desired point of entry.  The electrical sub on the project has now
>> proposed to reduce expense by replacing the RMC with cable trays and
>> running USE-2 in the cable tray from the JBOX back to the point of
>> entry.
>>
>> I'd appreciate your thoughts on the use of the cable tray and USE-2 on
>> the roof top.
>>
>> WIth REgards
>> Carl Adams
>> NABCEP cert 031508-1
>> _______________________________________________
>> List sponsored by Home Power magazine
>>
>> List Address: RE-wrenches at lists.re-wrenches.org
>>
>> Options & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>
>> List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>
>> List rules & etiquette:
>> www.re-wrenches.org/etiquette.htm
>>
>> Check out participant bios:
>> www.members.re-wrenches.org
>>
>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Options & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out participant bios:
> www.members.re-wrenches.org
>
>