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

Wed Aug 5 11:30:53 PDT 2009

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

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

Wrenches make design compromises every day. My 11 year old grid-tied system 
is an example:
- Siemens SP70 modules because SP75s were unavailable.
- Trace SW4048 at 65% efficiency because higher efficiency non-battery 
inverters were less reliable.
- Low-rise, low-tilt angle array because Culver City did not allow PV arrays 
to be visible from the street.
- And now, making improvements on a system that is working flawlessly for 
almost 100,000 hours does not make cost vs. benefits sense.

Joel Davidson

----- Original Message ----- 
From: "Dave Click" <daveclick at fsec.ucf.edu>
To: "RE-wrenches" <re-wrenches at 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 the 
> resistance 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 the 
> system with solid wire and have a voltage drop of (3% x 0.98) 2.94% at 
> peak 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.davidson at sbcglobal.net>
> To: RE-wrenches <re-wrenches at 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_solar at yahoo.com>
>> To: "RE-wrenches" <re-wrenches at 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 is 
>> larger than that.
>> Darryl
>>
>> --- On Mon, 8/3/09, Matt Tritt <solarone at charter.net> wrote:
>>
>>> From: Matt Tritt <solarone at charter.net>
>>> Subject: Re: [RE-wrenches] solid vs stranded  AC vs DC
>>> To: "RE-wrenches" <re-wrenches at 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 <jay at asis.com>
>>> wrote:
>>>
>>>
>>>
>>>     From: jay peltz <jay at asis.com>
>>> Subject: Re: [RE-wrenches] solid vs stranded  AC vs DC
>>> To: "RE-wrenches" <re-wrenches at 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 <jay at asis.com>
>>>
>>>
>>>     wrote:
>>>
>>>
>>>
>>>         From: jay peltz <jay at asis.com>
>>> Subject: [RE-wrenches] solid vs stranded AC
>>>
>>>
>>>
>>>     vs DC
>>>
>>>
>>>
>>>         To: "RE-wrenches" <re-wrenches at 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
>>> _______________________________________________
>>> List sponsored by Home Power magazine
>>>
>>> List Address: RE-wrenches at lists.re-wrenches.org
>>>
>>> Options & settings:
>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>>
>>> List-Archive: 
>>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>>
>>> List rules & etiquette:
>>> www.re-wrenches.org/etiquette.htm
>>>
>>> Check out participant bios:
>>> www.members.re-wrenches.org
>>>
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> List sponsored by Home Power magazine
>>>
>>> List Address: RE-wrenches at lists.re-wrenches.org
>>>
>>> Options & settings:
>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>>
>>> List-Archive: 
>>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>>
>>> List rules & etiquette:
>>> www.re-wrenches.org/etiquette.htm
>>>
>>> Check out participant bios:
>>> www.members.re-wrenches.org
>>>
>>>
>>>
>>>     _______________________________________________
>>> List sponsored by Home Power magazine
>>>
>>> List Address: RE-wrenches at lists.re-wrenches.org
>>>
>>> Options & settings:
>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>>
>>> List-Archive: 
>>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>>
>>> List rules & etiquette:
>>> www.re-wrenches.org/etiquette.htm
>>>
>>> Check out participant bios:
>>> www.members.re-wrenches.org
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> List sponsored by Home Power magazine
>>>
>>> List Address: RE-wrenches at lists.re-wrenches.org
>>>
>>> Options & settings:
>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>>
>>> List-Archive: 
>>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>>
>>> List rules & etiquette:
>>> www.re-wrenches.org/etiquette.htm
>>>
>>> Check out participant bios:
>>> www.members.re-wrenches.org
>>>
>>>
>>>
>>>
>>> No virus found in this incoming message.
>>> Checked by AVG - www.avg.com
>>> Version: 8.5.392 / Virus Database: 270.13.42/2279 - Release
>>> Date: 08/03/09 05:57:00
>>>
>>>
>>>
>>>
>>>
>>>
>>> -----Inline Attachment Follows-----
>>>
>>> _______________________________________________
>>> List sponsored by Home Power magazine
>>>
>>> List Address: RE-wrenches at lists.re-wrenches.org
>>>
>>> Options & settings:
>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>>
>>> List-Archive: 
>>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>>
>>> List rules & etiquette:
>>> www.re-wrenches.org/etiquette.htm
>>>
>>> Check out participant bios:
>>> www.members.re-wrenches.org
>>>
>>>
>>
>>
>>
>> _______________________________________________
>> List sponsored by Home Power magazine
>>
>> List Address: RE-wrenches at lists.re-wrenches.org
>>
>> Options & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>
>> List-Archive: 
>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>
>> List rules & etiquette:
>> www.re-wrenches.org/etiquette.htm
>>
>> Check out participant bios:
>> www.members.re-wrenches.org
>>
>>
>> _______________________________________________
>> List sponsored by Home Power magazine
>>
>> List Address: RE-wrenches at lists.re-wrenches.org
>>
>> Options & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>
>> List-Archive: 
>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>
>> List rules & etiquette:
>> www.re-wrenches.org/etiquette.htm
>>
>> Check out participant bios:
>> www.members.re-wrenches.org
>>
>>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Options & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: 
> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out participant bios:
> www.members.re-wrenches.org
> 