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

Dave Click Wed, 05 Aug 2009 12:42:02 -0700

> are we talking about 2% voltage drop, resistance, or power loss?

No- I was talking about the 2% difference in resistance between twowires, which is not the same thing as 2% voltage drop. What I got fromthis discussion was that solid copper wire will help your voltage dropby about 0.05%, a marginal benefit outweighed by the frustration ofexclusively using solid wire for wiring.

And sure, keeping losses low and not breaking wire strands at connectorsare important too. I did an inspection a few weeks ago where we openedup the panelboard and the original contractor for the building hadbroken off 3 strands from a #2/0 cable to fit it in the main lugs. Yikes!


DKC

-------- Original Message --------

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

From: Joel  Davidson <[email protected]>
To: RE-wrenches <[email protected]>
Date: 2009/8/5 14:30

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) usesolid copper wire and (2) keep I2R losses low and (3) if you usestranded wire, be very diligent when tightening connectors. Anything else?

Wrenches make design compromises every day. My 11 year old grid-tiedsystem is 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 PVarrays to be visible from the street.- And now, making improvements on a system that is working flawlesslyfor almost 100,000 hours does not make cost vs. benefits sense.


Joel Davidson


----- Original Message ----- From: "Dave Click" <[email protected]>
To: "RE-wrenches" <[email protected]>
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 a3% voltage drop in your system with stranded wire, you could rewirethe 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 <[email protected]>
To: RE-wrenches <[email protected]>
Date: 2009/8/3 20:31

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

----- Original Message ----- From: "Darryl Thayer"<[email protected]>

To: "RE-wrenches" <[email protected]>
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 conduithole is larger than that.

Darryl

--- On Mon, 8/3/09, Matt Tritt <[email protected]> wrote:

From: Matt Tritt <[email protected]>
Subject: Re: [RE-wrenches] solid vs stranded  AC vs DC
To: "RE-wrenches" <[email protected]>
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 <[email protected]>
wrote:

    From: jay peltz <[email protected]>
Subject: Re: [RE-wrenches] solid vs stranded  AC vs DC
To: "RE-wrenches" <[email protected]>
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 <[email protected]>

    wrote:

        From: jay peltz <[email protected]>
Subject: [RE-wrenches] solid vs stranded AC

    vs DC

        To: "RE-wrenches" <[email protected]>
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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