PV and New Residential Construction [RE-wrenches]

[Peter Parrish]

Well here we are two years later. We did what we thought was correct:
readily accessible DC disconnect before penetration, MC cable, protection
plates, labeling. The job is finished and now the inspector is insisting on
fusible DC disconnects. He claims that "no unfused conductors shall be
installed within buildings." What about the current-limited nature of the PV
string, and the series fuse rating? If we deployed interior cable for the DC
run with wires of sufficient ampacity (compared to series fuse rating of the
modules), is this not sufficient?

Can anyone cite NEC 2002 specifically allowing an un-fused disconnect? NEC
2005?

- Peter

Peter T. Parrish, Ph.D., 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 

-----Original Message-----
From: John Berdner [mailto:jberdner at sma-america.com] 
Sent: Tuesday, September 27, 2005 2:27 PM
To: RE-wrenches at topica.com
Subject: Re: PV and New Residential Construction [RE-wrenches]

Your free subscription is supported by today's sponsor:
-------------------------------------------------------------------
Need a new Cell Phone? A BlackBerry 7250 could be yours free! Find 
out how!
http://click.topica.com/caadV2bbz8QcsciXpi6a/Amazing phone
-------------------------------------------------------------------

Peter/ Wrenches:
 
John Wiles asked me to post this on his behalf.
 
Best Regards,
 
John Berdner
 
>>>

 
John Wiles wrote:
 
There are specific National Electrical Code requirements that apply to
these types of installations and some of the information presented by
others in previous posts does not follow those requirements.


In the 2002 NEC and prior editions of the NEC (adopted by California
and a few other states), all PV dc wiring must remain outside the
building or structure until reaching the first readily accessible
disconnect switch. Some local jurisdictions require the disconnect to be
mounted on the outside of the building, some allow it just through the
wall on the inside where the cables first penetrate the structure. 
These are generally the same requirements that apply to ac service
entrance disconnects in a given local.   Readily accessible (defined in
the NEC in Article 100) means that there can be no ladders required to
reach it, no building materials can be moved, and that no locks preclude
its operation.  So generally it cannot be in an attic unless there is a
permanent, fixed stairs leading to that attic.   The disconnect cannot
be located in bathrooms either.


The 2005 NEC (adopted by many states already)made an allowance (not a
requirement) for installing the PV dc conductors inside the building
before reaching that required, readily accessible disconnect.  Those
conductors must be in a metallic raceway.  Type NM cables have not been
evaluated for use in raceways.  Appropriate entrance weather heads for
USE-2 are available as are appropriate penetration devices if exterior
conduit is being used.


After that first readily accessible PV disconnect, the NEC allows any
wiring method suitable for the environment.  I endorse the suggestion
that circuit runs in the building be in EMT or one of the other metallic
raceways.


If you are installing PV systems, please get a copy of the NEC and
follow the requirements as well as those of your local jurisdiction. 
The life you save may be someone else's.


 
>>>

Wrenches



I am working with a home under construction and we plan to deploy
about
3,360W-STC of PV modules on three separate roof spaces. The client
wants the
PV DC runs to be routed in the same manner as the branch circuit
wiring:
drilling studs, routing Romex, etc. Inverter will be mounted on an
outside
wall.



It would seem that once indoors, I can assume dry conditions and an
ambient
of 40 deg C or less. 



The two questions I have are:



"Can I use NM cable with adequate protection (i.e. 1.25" of stud or
otherwise metal protection plates) as long as I observe the 1.56x
ampacity
correction?"



"Assuming that the j-box where I switch from say USE-2 to NM cable must
be
indoors, how accessible must it be? Attic space okay? And are attics
in
southern California rated at 40 deg or less?

Peter T. Parrish
California Solar Engineering, Inc.






--
[Non-text portions of this message have been removed]

Your free subscription is supported by today's sponsor:
-------------------------------------------------------------------
Ben & Jerrys. or Hdagen-Dazs.?
Take our Nationwide Ice Cream Survey today! Receive a FREE* $100 
Restaurant Gift Card of your choice or $100 worth of Ben & 
Jerrys. or Hdagen-Dazs. ice cream for participating!
http://click.topica.com/caadVYQbz8QcsciXpi6f/Ice Cream Research Survey
-------------------------------------------------------------------

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

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

List rules & how to change your email address:
www.mrsharkey.com/wrenches/etiquette.php

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

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com


- - - -
Hosted by Home Power magazine

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

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

List rules & how to change your email address: www.mrsharkey.com/wrenches/etiquette.php

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

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

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
--^----------------------------------------------------------------