PV and New Residential Construction [RE-wrenches]

Jeff Clearwater clrwater at earthlink.net
Mon Sep 26 20:11:07 PDT 2005


<x-flowed>
Hi Peter, Barbara and all,

Whether Barbara's description is enforced code in your area or not, I 
would ABSOLUTLEY follow it.  I think one of the biggest risks the PV 
industry bears is some homeowner getting electrocued someday by high 
voltage DC.  Most homeowners and even most electricians - when they 
see romex are going to assume they can tap into the line to install a 
plug or light or some such.  It's a formula for disaster.

Even before we were aware of the code on high voltage DC wiring in 
residences, we always put our high voltage DC wire in EMT and always 
labeled it.  It's the only sane way to go - code applicability, 
enforcement or not.  I strongly suggest all do the same.  If you use 
pull boxes - make sure they are labeled too!

Best,

Jeff Clearwater
Village Power Design



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>Peter -
>
>Not knowing what jurisdiction you are working under, please know that we are
>aware of the following:
>
>All DC wiring within walls and/or in attic must be in some type of metallic
>conduit (EMT, Rigid, IMC, BX, Flex) and must be identified (use a sharpe)as
>HV DC SOLAR.  The DC wiring cannot enter the interior of the house/attic
>more than 10' before it lands on the DC disconnect.  Continuing the DC run
>through the walls must be in metallic conduit (same as above).  The reason
>given for this:  The building department does not want a remodeler,
>electrician, etc... to start modifying/demoing a wall using the typical
>means of a sawzall, or other such device and sustain an injury cutting thru
>the hot DC wiring.  It is their belief that hitting the metallic conduit
>will immediately alert them that something unusual is present in the wall,
>and hopefully cause them to cease and investigate before they get to the
>actual DC wires.  Once the Senior Building official explained this to us, we
>supported it 100% as a life safety issue.
>
>Typically, if the attic access allows for a person to "easily" reach the DC
>disconnect (meaning that it is within an arms length of the opening) from a
>ladder it is okay. 
>
>Best o' Luck
>
>Barbra Kerr
>
>
>
>-----Original Message-----
>From: Peter Parrish [mailto:peter.parrish at calsolareng.com]
>Sent: Monday, September 26, 2005 6:23 PM
>To: RE-wrenches at topica.com
>Subject: PV and New Residential Construction [RE-wrenches]
>
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>
>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]
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-- 
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design Associates
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com
gosolar at villagepower.com

530-470-9166
877-SOLARVillage
877-765-2784
425 Nimrod St.
Nevada City, CA 95959
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`~

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