[RE-wrenches] PV System Design Compromises (was solid vs stranded AC vs DC)
Joel Davidson
joel.davidson at sbcglobal.net
Wed Aug 5 14:37:27 PDT 2009
Matt, Right-on. I meant solid smaller gauge wire and multi-stranded larger gauge wire as compared to finely-stranded wire.
Dave, Almost every electrician has nipped off a strand or more to get a conductor to fit into undersized connectors. Older model charge controllers and inverters were notorious for undersized connectors. Some electricians are very skilled at fitting lugs and/or putting tape over "down-sized" wire ends. I'm not justifying this practice. Just reminding manufacturers to provide big enough connectors that are securely fastened to their equipment (not tacked onto a circuit board) and to provide practical strain-reliefs.
Joel Davidson
----- Original Message -----
From: Matt Tritt
To: RE-wrenches
Sent: Wednesday, August 05, 2009 1:29 PM
Subject: Re: [RE-wrenches] PV System Design Compromises (was solid vs stranded AC vs DC)
Joel,
Changing any wires connected to a SW to solid core would be virtually impossible because of the almost impossible to connect with stranded wire connection blocks. Remember how ^$*! tight the spaces are in those babies? Living with a marginally relevant inefficiency from stranded seems a low price to pay for being able to connect the bits and pieces to each other. Non?
Matt T
Joel Davidson wrote:
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
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