Peter,
Inspectors in Southern California and elsewhere see, on all kinds of
buildings, properly installed roof-mounted conduit crushed, broken, and with
fittings pulled apart after the installation is completed by clumsy,
ignorant unskilled people on the roof. I'm not defending inspectors who make
arbitrary judgments. I'm just pointing out that unknowing people and jerks
will step on your conduit and screw it up. Add a written up-charge to your
proposals and contracts when rigid is required.
I think most wrenches will agree that fastening anything (wire, conduit,
antennas, etc.) to chimneys and vent pipes is convenient but unwise.
Joel Davidson
----- Original Message -----
From: "Peter Parrish" <peter.parr...@calsolareng.com>
To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org>
Sent: Friday, March 06, 2009 10:55 AM
Subject: [RE-wrenches] Chimneys Rigid vs EMT
We have an interesting situation in the enclave of Pasadena, CA.
(1) The Pasadena Building and Safety Department is requiring the use of
rigid conduit (only) on any DC and AC runs for grid-tied PV systems. They
specifically prohibit EMT, LFNC and LFMC. This requirement applies to any
DC
or AC runs on the roof, and it applies to any DC or AC runs on exterior
walls.
They do not require the use of rigid conduit on A/C equipment, lighting or
any other piece of equipment requiring exterior-mounted conduit conveying
electrical power.
(2) They also disallow a rigid conduit run anywhere on the exterior
surface
of a chimney. Where a conduit run on an exterior wall encounters a
chimney,
they require that the conduit run follow the line where the chimney meets
the wall/roof. This means up the wall, along the roof and back down the
wall.
Although I think (1) is overkill, I will comply this once and engage the
AHJ
before the next job we have in this town; I have graver reservations about
(2). I have lived over 50 years in California and I have seen the results
severe earthquakes can have on residential chimneys. If the chimney goes,
the first place it happens is on the unsupported portion above the roof.
The
next place the chimney fails is the higher portion, attached to the
building
frame. I think I can remember just one case where a chimney failed within
3
feet of the foundation, and in that case most of the rest of the structure
failed. Consequently if a chimney fails, there will be hundreds of pounds
of
brick raining down on the rigid conduit where it runs along the chimney
roof
interface.
I would argue that the safest place for a rigid conduit run would be
around
the chimney in the crawl space (if any) underneath the house, attached to
floor joists. If that option is not available I would argue for a run
around
(and anchored to) the exterior chimney at about 2-3 feet above grade.
Is item (2) essentially a B&S issue not addressed by the Fire Department?
Has anyone encountered these sorts of requirements elsewhere?
Comments?
- Peter
Peter T. Parrish, President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parr...@calsolareng.com
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