PV combiner box protection [RE-wrenches]

Ray Walters ray at solarray.com
Thu Jun 24 10:53:56 PDT 2004


<x-flowed>
Your free subscription is supported by today's sponsor:
------------------------------------------------------------------
Get a FREE Mortgage Quote from Mortgage War. Simple application 
for mortgage information. If you're ready to get a quote click 
now!
http://click.topica.com/caacneLbz8Qcsbz9JC9a/411Web
------------------------------------------------------------------

Hi Phil;

All I can tell you is that many people are not going to be able to afford 
your way, and they're going to keep daisy chaining to infinity. I'm trying 
to offer a compromise that is safe and reasonable even if its not to code. 
12 volt systems usually aren't to code anyway because so much of the 
equipment( controllers, pumps, etc. are not
UL listed) What I propose for these compromise systems is a  15 amp QO 
breaker and box at the pole, array wiring with 12 -2 TC, and less than 10 
amps total array current per 15 amp breaker. We then bring the combined 
current from the pole into the system with larger wire, again I size for 
ampacity and energy savings, not blindly to the 2% rule.(see my previous 
posts on wire sizing for watts lost, not voltage)
  In poor communities, third world etc. this is light years beyond what 
they are normally doing. I see salvage NMB wire twisted straight around 
battery posts, etc.(no fuses, no controller) I'm not saying all you 
California Grid tie guys should abandon the NEC, I'm just trying to bring a 
few of these really dangerous  out there systems under control. If some 
retired person dies in a solar electric related fire, its going to look bad 
for all of us regardless of how poorly it was wired .
Oh as an aside, the non-installer dealers are really contributing to these 
unsafe systems, by selling panels and batteries without any design help or 
fusing.

Bottom line: some fusing is better than nothing

Ray

PS If we really wanted to take care of the problem, we should push for some 
grant funding to go out and bring all these marginal systems into the fold 
before something happens. A little TLC now would be cheaper than a damage 
control PR campaign.

> >Come on, you're really going to bring
> > each 50 watt module in a 12 volt system in on a separate wire and breaker?
> >
> > Ray
>
>Yes, but not necessarily like you may think.  A 50 watt module = 3 amps at
>12v.  That means #10 wire is good for about 50-60'.  In a system with less
>than 2-300 watts of array, I'd consider running separate feeds back to a
>Square D 6-12 box located at the power system (which could also serve as
>array disconnect), or 1/4" ABC fuses at the array.  More array than that, or
>the array run is further than 60'?  Consider adding MPPT.  And if you add
>MPPT it's only a small jump to a higher voltage array.
>
>When you consider the cost of the raintight J-box at the array, the cost of
>the splitbolts and splicing tape, and the labor getting a half-dozen wires
>into that splitbolt and protected, and the labor it takes to undo that
>splitbolt and splicing tape the first time you want to check module output,
>I just don't see that much $$$ saved by eliminating the  series fusing.
>
>Phil

Your free subscription is supported by today's sponsor:
-------------------------------------------------------------------
Save up to 67% on Omaha Steaks + Get 6 FREE Burgers and a 
FREE Cutlery Set + Cutting Board!
http://click.topica.com/caaclxSbz8Qcsbz9JC9f/OmahaSteaks
-------------------------------------------------------------------

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



</x-flowed>



More information about the RE-wrenches mailing list