[RE-wrenches] Chimneys Rigid vs EMT

[Joel Davidson]

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.parrish at calsolareng.com>
To: "'RE-wrenches'" <re-wrenches at 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.parrish at calsolareng.com
>
>
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