DC Runs in the Attic [RE-wrenches] DC arc fault

Sun Sep 19 09:51:37 PDT 2004

Your free subscription is supported by today's sponsor:
-------------------------------------------------------------------
Sponsor a child today through Children International.  
Give a desperately poor child hope for a brighter future.
For only $18 a month you can make a difference!
http://click.topica.com/caacBBFbz8Qcsbz9JC9a/ChildrenInternational
-------------------------------------------------------------------

The last thing we need is a requirement for a DC ARC FAULT DETECTOR on the
lines from panels to the box.
Your kidding, RIGHT?
I am not convinced that the AC arc fault breakers work correctly at this
point.

Bob

RE. Ellison
Supplier of;
Alternative Energy Systems & Supplies
34642 Countryman Road
Theresa, NY. USA
                               13691-2076

-----Original Message-----
From: Gary Higbee [mailto:gary at windstreamsolar.com]
Sent: Sunday, September 19, 2004 3:20 AM
To: RE-wrenches at topica.com
Subject: Re: DC Runs in the Attic [RE-wrenches]

Your free subscription is supported by today's sponsor:
-------------------------------------------------------------------
Sponsor a child today through Children International.
Give a desperately poor child hope for a brighter future.
For only $18 a month you can make a difference!
http://click.topica.com/caacBBFbz8QcsbfmDywa/ChildrenInternational
-------------------------------------------------------------------

Mark and Wrenches,

Oh, yes PV through the attic. As an inspector I'm supposed to back up code,
but most importantly make sure contractors meet the Energy Trust of Oregon
requirements. The issue of runs through the attic is not new to Oregon, and
I've seen several examples of local jurisdictions allowing it, not allowing
it, or allowing it with a disconnect on the roof. I've heard of a fused
pass-through box, too. My opinion is that PV is growing beyond a simple
"add-on," that we need to address building integration, and that this is
important.

At this point there are jurisdictions in Oregon I am aware of who allow PV
runs through attic space so long as they are in metallic conduit--citing a
'05 code change as justification.

Some thoughts (and please check me on this!):

1) The idea of a PV disconnect on the roof escapes my logic. Aren't
disconnects supposed to be accessible? If this is as I read things then if
there is a disconnect on the roof I expect to see a code-compliant staircase
leading up there. Let's make sure the treads are right, folks, and those
handrails had better be just right. Oh, watch the reach to the disconnect,
too! Unless I see a good and/or code-requiring argument otherwise I would
flag a DC disconnect (if that's what it is called) on the roof as a safety
violation--unless the above stairs and rails were carefully attended to--an
absurd proposition, of course.

2) Using a fused pass-through box is equally absurd, right? After all, by
NEC the fuses must be sized beyond the maximum short-circuit current of the
array. A fault will sit there and fry every day without blowing a fuse,
won't it? What's the point here, other than to satisfy a naive electrical
inspector?

3) Other wiring ideas? Well, I think many of us do see the potential risks
of stapled cable of a limited current source (that might happen to be
pierced) sizzling away against the rafter. What happens when things dry out
enough to say goodbye to the attic, and maybe house and residents. Doesn't
seem wise to me, and this would be a major violation in my book.

4) Using metallic conduit sounds like a step in the right direction. Let's
say there's a nick in a wire or two, though, and a nice little arc plays
around every day--until the EMT gets really hot or eventually burns through.
Is this realistic, possible?

5) Is there any such thing as a DC arc-fault breaker that could go on the
roof? Would the safest solution be an arc-fault breaker on the roof, and
then any reasonable wiring method beyond that? In this case would not the
stapled and/or nicked wires, or whatever might generate an arc, turn off the
source? Is metallic conduit really a reasonable solution, or is it a
temporary work-around until we get DC arc-fault breakers on the roof? And if
we do that then is this considered a disconnect (and thus subject to
accessibility)?

It seems to me that the best solution would be an arc-fault detector on the
roof and a DC disconnect prior to the charge control (battery-based) or
inverter, along with reasonable wiring practices through the attic or other
enclosed space (in metallic conduit or not). This way we have a DC
disconnect prior to the first electronics the modules meet, and importantly,
we also have catastrophic fault protection prior to an enclosed space.

Thoughts?

Gary

*****
----- Original Message -----
From: "Mark Byington" <markbyington at sbcglobal.net>
To: <RE-wrenches at topica.com>
Sent: Saturday, September 18, 2004 9:15 PM
Subject: DC Runs in the Attic [RE-wrenches]

A local inspector in CA is interpreting 230.70 to mean we cannot run the DC
line from a roof mounted PV array through the attic of a residence to the DC
disco mounted on an exterior wall.  His justification is that the DC run is
a service entrance conductor.  He is worried about fire hazard.  The code
does say it is up to the local jurisdiction...
*****

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                     ~ Windstream Solar ~
     Gary Higbee  (gary at windstreamsolar.com)
                     (541 ) 607-1818 (Eugene)
                        (541) 954-3881 (Cell)
Solar, wind, and hydro site analysis and system design
    Components dealer and installation assistance
 Energy Trust of Oregon contracted system inspector
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Your free subscription is supported by today's sponsor:
-------------------------------------------------------------------
Are Americans getting fat? Give us your opinion and win.
http://click.topica.com/caacDvYbz8QcsbfmDywf/PermissionData
-------------------------------------------------------------------

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read

List rules & etiquette: www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

Your free subscription is supported by today's sponsor:
-------------------------------------------------------------------
Click here and walk away with your free Chevy collectible.
http://click.topica.com/caacDvMbz8Qcsbz9JC9f/PermissionData
-------------------------------------------------------------------

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read

List rules & etiquette: www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com
--^----------------------------------------------------------------
This email was sent to: michael.welch at homepower.com

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

For Topica's complete suite of email marketing solutions visit:
http://www.topica.com/?p=TEXFOOTER
--^----------------------------------------------------------------