[RE-wrenches] PV System Design Compromises (was solid vs stranded AC vs DC)

Joel Davidson Wed, 05 Aug 2009 11:42:05 -0700

Dave, I agree. but are we talking about 2% voltage drop, resistance, orpower loss?

What I got from this discussion about solid vs. stranded wire (1) use solidcopper wire and (2) keep I2R losses low and (3) if you use stranded wire, bevery diligent when tightening connectors. Anything else?

Wrenches make design compromises every day. My 11 year old grid-tied systemis an example:

- Siemens SP70 modules because SP75s were unavailable.

- Trace SW4048 at 65% efficiency because higher efficiency non-batteryinverters were less reliable.- Low-rise, low-tilt angle array because Culver City did not allow PV arraysto be visible from the street.- And now, making improvements on a system that is working flawlessly foralmost 100,000 hours does not make cost vs. benefits sense.


Joel Davidson

----- Original Message -----From: "Dave Click" <davecl...@fsec.ucf.edu>

To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Sent: Wednesday, August 05, 2009 5:58 AM
Subject: Re: [RE-wrenches] solid vs stranded AC vs DC

2% loss is significant, but I think that Darryl was saying that theresistance for stranded wire was 2% higher than solid. So if you had a 3%voltage drop in your system with stranded wire, you could rewire thesystem with solid wire and have a voltage drop of (3% x 0.98) 2.94% atpeak production; that's less than 1 kWh/yr per kW installed.


DKC

-------- Original Message --------
Subject: Re: [RE-wrenches] solid vs stranded  AC vs DC
From: Joel  Davidson <joel.david...@sbcglobal.net>
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
Date: 2009/8/3 20:31

2% loss from any resistance source over 25 years is significant.

----- Original Message ----- From: "Darryl Thayer"<daryl_so...@yahoo.com>

To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Sent: Monday, August 03, 2009 2:04 PM
Subject: Re: [RE-wrenches] solid vs stranded AC vs DC

Yes, that is what the code book and my electricians handbook says, but 2%is very little. I would think that passing through a conduit hole islarger than that.

Darryl

--- On Mon, 8/3/09, Matt Tritt <solar...@charter.net> wrote:

From: Matt Tritt <solar...@charter.net>
Subject: Re: [RE-wrenches] solid vs stranded  AC vs DC
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Date: Monday, August 3, 2009, 3:49 PM






Darryl,



Say what?! This would seem to indicate that solid core is
actually
better for DC than stranded wire. Can this possibly be
true??



Matt



Darryl Thayer wrote:

  I looked in the code book and found stranded wire
has about 2% higher DC resistance than solid, Chapter 9
table 8, and that for AC resistance the same value as DC
resistance to within the table accuracy Chapter 9 Table 9

This table points out that for AC resistance it is
important to know the conduit system, as the reactance will
have an effect.  With AC it is important to never allow a
single wire to pass through a metal surface as this will
induce eddy currents and magnetic effects into the metal
causing voltage drop and heating.

--- On Fri, 7/31/09, jay peltz <j...@asis.com>
wrote:



    From: jay peltz <j...@asis.com>
Subject: Re: [RE-wrenches] solid vs stranded  AC vs DC
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Date: Friday, July 31, 2009, 10:01 PM
Hi Darryl,

But what are the differences and when do they come into
play?




On Jul 31, 2009, at 7:25 PM, Darryl Thayer wrote:



      Well there is very slight differences between AC
and


    Dc But this


      difference
is so slight that it has no effect on anything we will


    do.


      Darryl
--- On Fri, 7/31/09, jay peltz <j...@asis.com>


    wrote:



        From: jay peltz <j...@asis.com>
Subject: [RE-wrenches] solid vs stranded AC



    vs DC



        To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>
Date: Friday, July 31, 2009, 7:00 PM
HI All,

I'm trying to understand this wire issue.

Whether or not there is a difference between



    stranded or



        solid wire for DC or AC.

Any takers on this one?

thanks,

jay

peltz power
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