voltage drop calculations

[Smart $]

It's becoming clear to me that the spreadsheet needs more columns, e.g., wire resistance for the distance for AL, same for CU, $/ft for that gauge AL (which depends on the length purchased), same for CU, and a sum posted at the bottom of these last two columns.

The optimum for voltage drops is almost certainly not the same as the optimum for cost, since physics does not take supply & demand into account.
This larger spreadsheet will, though.

So when are you going to post this larger spreadsheet?

FWIW, I calculated voltage drop for a 120/240 3-wire circuit, putting 5 lamps on each leg. #8 for the whole run comes in at a tolerable 3.4% Vd, with 115.91V at last lamp. Smaller conductors but one more, so that would be another cost comparison.

 

[Electron_Sam78]

Here's what I got with my calculator. I can play around with different wire sizes and material to adjust each leg

 

[G._S._Ohm]

Posting spreadsheets for me has not worked, but I can post what formulas are in each cell and how they interact.

For some copper wire sizes in some lengths you pay about one cent per CM, according to Nextag. What are reasonable costs for the sizes we are discussing here?

The extreme cases seem to be
one wire size for all, or
10 different sizes (not practical),
with the 'best' case being somewhere in the middle and depending on the cost of breakers/fuses for the smaller wires.

 

[Smart $]

Posting spreadsheets for me has not worked...

Not unexpected, as valid forum attachments do not include spreadsheet formats... but what I have done in the past was to embed the (Excel) spreadsheet in a (Word) doc file, then attach it.

For some copper wire sizes in some lengths you pay about one cent per CM, according to Nextag. What are reasonable costs for the sizes we are discussing here?

Costs are not my area. I looked up some online prices for #8 copper THHN/THWN and it seemed to run about $225 to $250 for 500'.

 

[G._S._Ohm]

Somewhat in line with one of my posts, if you use the same size wire throughout, 0.19375 ohms per 1000' should do it. Depending on what table you use, this comes out to the DC resistance of #2 uncoated copper at 75C.

I'll go one click thicker in wire size for the 400' and one click thinner for the rest and see what that gets me.

 

[G._S._Ohm]

#1 and #3 gives 120.05v. Close enough.
If the price for this 1 & 3 combo is less than that for #2 used for the whole length then this is heading in the right direction.