[RE-wrenches] 690.32(E) + MC?

[Dave Click]

I believe that in a Code Corner back in the '05 era, John Wiles had said 
that MC cable was OK to use, then in a later Code Corner he says that it 
isn't; I thought it was because part of the reason for a metal raceway 
is physical protection, and EMT/FMC would be sturdier than MC. But then 
I looked at the 2011 Code, which (as it currently stands) will allow MC:

(E) Direct-Current Photovoltaic Source and Output Circuits Inside a 
Building. Where dc photovoltaic source or output circuits from a 
building-integrated or other photovoltaic system are run inside a 
building or structure, they shall be contained in metal raceways, Type 
MC metal clad cable that complies with 250.118(10), or metal enclosures, 
from the point of penetration of the surface of the building or 
structure to the first readily accessible disconnecting means. The 
disconnecting means shall comply with 690.14(A), (B), and (D). [ROP 4-228]

The new 690.31(E) is about ten times longer than the '08 edition, now 
requiring the conduit to be >10" below the surface of the roof (to avoid 
firefighting equipment venting the roof) and labeling along that conduit 
too:
http://www.solarabcs.com/index.php?option=com_docman&task=doc_download&gid=248&&Itemid=72

And to save you a lookup:
250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor run with or enclosing the circuit 
conductors shall be one or more or a combination of the following:
...
(10) 	Type MC cable where listed and identified for grounding in 
accordance with the following:
a. 	The combined metallic sheath and grounding conductor of interlocked 
metal tape–type MC cable
b. 	The metallic sheath or the combined metallic sheath and grounding 
conductors of the smooth or corrugated tube-type MC cable

-------- Original Message --------
Subject: Re: [RE-wrenches] 690.32(E) + MC?
From: R Ray Walters <ray at solarray.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Date: 2009/12/5 03:28

> I think the issue here is 690.32 deals just with 'fittings and
> connectors', not the actual wire or cable. I believe you meant to
> reference 690.31 which says 'all raceway and cable wiring methods
> included in this code....shall be permitted'. But you still have to
> comply with 690.31E which says it needs to be in 'metal raceways or
> metal enclosures' once it enters the building up to the first readily
> accessible disconnect. Looking at article 100, the definition of
> raceway does include flexible metal conduit, so it seems you could
> use metal flex conduit and pull wire, but I know many inspectors
> still won't allow it. Reading up in articles 320 and 330 for AC and
> MC cables, MC doesn't say it's conduit, so it would be out, but AC
> says its enclosed in a 'flexible metallic enclosure'. So now the
> question is: Is metallic the same as metal? (Oh Boy are we splitting
> semantic hairs now.......). Bill or William are the ones to clarify
> better than I on all of this, though. They've been involved in the
> actual writing of the code. IMHO, it seems yet another point to be
> clarified in future additions of the code. Meanwhile to be safe, most
> of us are just running EMT once we penetrate the building. (which
> opens yet another question: when have you penetrated the building?
> above or below the roof flashing?)
> 
> I think I've caused enough trouble for now,
> 
> R. Walters ray at solarray.com Solar Engineer
> 
> 
> 
> 
> On Dec 4, 2009, at 7:47 PM, Darryl Thayer wrote:
> 
>> I have always read metal conduit, The reason being the solar is
>> unfused source circuits, and there is no way for overcurrent
>> protective devices to open.  Therefore, the conductors must be
>> protected from starting a fire under conditions of continuous
>> overcurrent. darryl
>> 
>> 
>> --- On Fri, 12/4/09, dan at foxfire-energy.com
>> <dan at foxfire-energy.com> wrote:
>> 
>>> From: dan at foxfire-energy.com <dan at foxfire-energy.com> Subject:
>>> [RE-wrenches] 690.32(E) + MC? To: "RE-wrenches"
>>> <re-wrenches at lists.re-wrenches.org> Date: Friday, December 4,
>>> 2009, 5:18 PM I did a project a while ago for a supplier /
>>> Installing out fit (who has their in house engineering types),
>>> who told me that either MC or maybe AC cable did comply with
>>> 690.32E. today I'm being told that's not the case, and I can't
>>> seem to put my finger on it ... any pointers? thanks db
>>> 
>>> 
>>> Dan Brown President Foxfire Energy Corp. Renewable Energy Systems
>>>  (802)-483-2564 www.Foxfire-Energy.com NABCEP #092907-44
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
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