[RE-wrenches] calculating DC voltage drop

[R Ray Walters]

I try to keep it in copper for DC, as I had always heard of trouble with Aluminum on DC. (True or Old Wrenches Tale?)
We definitely go to Al on long AC runs, as its whats available, and the cost difference becomes remarkable.
I've seen small cuts in Al, later corrode completely through the conductor.(AC run) I'm not sure what would happen it were DC.
Probably depend on whether it was positive or negative, and which was bonded to ground? (either accelerate the corrosion, or act as cathodic protection?)

R. Walters
ray at solarray.com
Solar Engineer




On Jul 23, 2010, at 6:14 AM, Richard L Ratico wrote:

> All,
> 
> For longer, underground, array to inverter/charge controller runs, are folks
> using aluminum or copper?
> Last time I compared prices, for the same ampacity, Al was 1/3 the cost of Cu.
> 
> Dick Ratico
> Solarwind Electric
> 
> --- You wrote:
> Hi Dana;
> 
> I'd say that's a bit overkill for today's market. That money could be making
> more power, not just preventing losses. 
> Definitely a law of diminishing returns on wire sizing. 
> If you allocated 50% of the budget to wire, and 50% to PV, your losses would be
> very low, (immeasurable but unfortunately still there) but your total system
> production vs. the money spent would be terrible.
> I'm only using this ridiculous example to show, that at some point, we all spend
> money on more PV, not bigger wire. 
> I pick that point based on sound economic analysis, not some over applied rule
> of thumb. As copper costs rise, and PV gets cheaper, that point moves up. 
> If copper was still at 20th century prices, and PV were $10/ watt, your 1% might
> very well be the right answer.
> 
> ( this is also the point where Bob-O starts hammering me, so I'd better run.
> $E2opi$E2o$BA)
> 
> R. Walters
> ray at solarray.com
> Solar Engineer
> --- end of quote ---
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