[RE-wrenches] DC Discos for Enphase

[SOLARPRO at aol.com]

Matt:
 
Well, thankyou for showing me the dance steps.... but don't  think I'll 
stop worrying about this one.  I doubt I'll ever bring a  skillsaw into 
Planning and Building, which is where the dance begins  and usually ends.  Besides, 
I went cordless a looong time ago and all I  ever carry into the inner 
sanctum, the place where the meat hits the  grinder, is a ten pound roll of plan 
sets, my i-phone and a box of donuts.  But I am so glad to know, per 
690.17, that a connector which is listed as a  connector can also be considered to 
be listed as a  dis-connector.
This just seems too logical.
 
Pat Redgate
(Yawn)
 
 
In a message dated 9/14/2010 11:48:12 A.M. Pacific Daylight  Time, 
gilligan06 at gmail.com writes:

Stir  away....
 
Modern locking module  connectors serve as DC disconnects for 
micro-inverters. This  point was alluded to in the Code Corner sidebar, but not addressed 
in  detail. It takes a little  dance along Route 690 to drive the point 
home to OCD-afflicted AHJs...  But it's right there...
 
The simplest dance  steps generally start with 690.14(A). This clause 
specifically says  disconnects don't have to be suitable as service equipment and 
must  comply with 690.17. 690.17 requires disconnects to be manually  
operable switches or breakers that meet a host of requirements. And then  there's 
the exception, which throws all that out the window... Or off the  roof, as 
the case might be. (Exception: A connector shall be permitted to be  used 
as an ac or a dc disonnecting means, provided that it complies with the  
requirements of 690.33 and is listed and identified for the use.) Listed  and 
identified as a PV connector meets this requirement. 
 
As your AHJ is  quivering with OCD discomfort... Quickly flip to 690.33 to 
send him/her into  full-on convulsions... 
 
690.33 requires connectors to be  polarized, noninterchangeable with other 
stuff on the premises, guarded live  parts, latching or locking, require a 
tool to open, 1st make/last break  grounding member and... Either be rated 
for interrupting current without  hazard to the operator OR require a tool to 
open and marked "Don't open under  load". 
 
Demonstrate your compliance to the AHJ this way: Flip  your module over, 
grab both connectors, plug them into each other, yank on the  wires to 
demonstrate that a tool is required to open the connector, and flick  the 
sticker-tape labels that say "Do Not Disconnect Under Load". Hand the  connection to 
your AHJ. Make hm or her check it out closely. While he/she is  examining 
the connection, reconciling in their own head the irrational  concept that a 
disconnect doesn't have to be a switch here.... Turn the module  to face the 
sun and point out to them that they are now holding an energized  dead 
short. Just for fun :)
 
If they can't wrap their head around the  concept, take them over to your 
work truck. Pull out a skilsaw. Show them the  nameplate amps and discuss the 
power of the tool. Way more watts and  higher voltage than your module. 
Carry the thing over to a live  receptacle, plug it in, squeeze and hold the 
trigger, pull the plug out of the  receptacle. Happens every day with all 
kinds of tools and appliances.  There's no label on the cord or  receptacle to 
say you can't... 
 
Now compare this to your module connectors  to demonstrate how much safer 
and more effective the locking, labeled  connectors are. Buried up there 
behind the modules and all. Where only a  qualified person can get to them. 
Where, in the event of an emergency,  shutting down the ac circuit reduces the 
maximum potential current to one  module. No matter how bad the fault is or 
where it's located. Which is the  lowest possible unit of energy in a modern 
PV system. Can't get much safer  than that!
 
Hope it didn't take too long to fall  asleep...
 
Matt  Lafferty
 
_gilligan06 at gmail.com_ (mailto:gilligan06 at gmail.com) 
 

 
____________________________________
 From: re-wrenches-bounces at lists.re-wrenches.org  
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of  SOLARPRO at aol.com
Sent: Tuesday, September 14, 2010 10:19  AM
To: re-wrenches at lists.re-wrenches.org
Subject:  [RE-wrenches] DC Discos for Enphase



Howdy Wrench  
I don't try to stir things up, but I was just wondering last night as I  
fell asleep reading the latest issue of HomePower magazine (# 139), if anybody 
 else caught a chill when they read this in the Code Corner (highlighted in 
a  box):
 
"Both microinverters and microinverters attached to PV
modules in the  field or in the factory that have any exposed
DC single conductor cables  are required to meet all of the
NEC’s DC wiring requirements. These may  include Section
690.5 ground-fault detector requirements, DC and  AC
disconnect requirements (potentially handled by connectors
listed as  disconnects), and inverter DC grounding-electrode
requirements."
- John Wiles
 
 Which begs the question: Are <any> module connectors  currently listed as 
disconnects?
 As well as: If DC voltages for each disconnect are less than 48  V, would 
a simple  switch suffice, should the poor hapless installer  run into an AHJ 
with OCD?    
 
 
Patrick A.  Redgate
AMECO Solar, Inc.
Serving Solar  California
Since 1974
7623 Somerset, Blvd.
Paramount, CA  90723
562-633-4400



_www.solarexpert.com_ (http://www.solarexpert.com/) 
_www.amecosolar.com_ (http://www.amecosolar.com/) 



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