Ok here is the thing, pipe is existing 1&1/2 pvc 425 feet long 60 a overcurrent at the main panel,, the load at the barn is about 48 amps as a guess. Whats the largest size copper conductors and or alr. conductors that can be pulled?? So far I came up with 3 3/0 alr. with no ground, drive a ground rod at the barn and call it a day, or three number 1/0 and one # 6 copper. What do you guys think?? The huge issue is the 1&1/2 pvc thats undersized.
It looks like 2005 NEC 250.32(B)(2) allows you to run your feeder without an EGC, as long as there are no parallel paths for normal neutral current. So, that could be an option
if there is no metal water pipe, etc. I don't particularly like going that route, but it appears it would be Code compliant, given that you're still on '05.
Now that we have that out of the way, you can't run 3#1/0 & 1#6 EGC (copper) for a 60A circuit. NEC 250.122(B) requires your EGC to be "increased in size proportionately according to the circular mil area of the ungrounded conductors." So let's do the math.
#1/0 circular mils / #6 circular mils = 105600 / 26240 = 4.024
The normal size for a copper EGC on a 6A circuit is #10 (see Table 250.122), so we need to increase it by multiplying its circular mils by 4.024:
10380 x 4.024 = 41773 circular mils
This is just barely larger than #4 AWG, so you need to go up to the next larger size -- hence, your EGC needs to be at least #3 AWG.
Assuming THWN conductors, 3#1/0 & 1#3 EGC will take up 0.6538 in
2 (Chapter 9, Table 5). This will work in your 1-1/2" PVC (whether it's Schedule 40 or 80 -- see Chapter 9, Table 4).
You'll still need to check your pulling tensions in a run that long, though.
Oh, and by my calculations, for a 425' run of #1/0 copper conductors at 120/240V, single phase, drawing 48A, the voltage drop will be about 2.21%. At 60A it would increase to about 2.76%.
Hope all this helps.