Pond Boss Forums INTRO Questions & Observations electrical guru's take notice

If running just single phase 120VAC, the neutral ("white") has to be the same size as the hot ("black"), because the load will be running over both of these wires.

I have seen a size smaller neutral used when running 240VAC three-wire edison (2-phase), on the theory that enough of the load will be either 220VAC or balanced 110VAC of opposite phases that the neutral will be carrying a smaller load than either hot wire. I have not put this theory into practice myself, but have bitten the bullet to buy just as heavy a wire for the neutral as the hots when running 240VAC. (Downsizing 1 wire out of 3 saves perhaps 10%-20% on total wire cost. If not using 240VAC exclusively, why bet your loads will always be balanced for that small amount?)

I suggest a local ground rod to supply the ground in either case; this of course eliminates the need for a long ground wire and (properly done) is more effective as well. One shouldn't have trouble getting a good ground near a pond (unless it's lined).

IF I understand the wire you plan on using correctly, 8-10-12 gauge black and 10 gauge white, I think the limiting factor would be the stretch of 12 gauge black, not a whole length of 10 gauge white. I believe the exact answer would depend on the length of the 8, 10, and 12 gauge segments, but unless the 12 gauge is very, very short, it's going to be the overall load limiter (not the 10 gauge white).