[HayZee518]

first of all the calculated voltage drop cannot be more than 3% per hundred feet. if you were to feed the shed I'd have to know what the anticipated load would be - what you intend to run from there. the feeder would need to be a four wire becaue a sub-panel has an isolated neutral, an equipment ground and two hots. as far as the well pump goes, the installation guys really don't follow a certain code they just run a triplex 12 and hope for the best. IMO for a well a 10/3 might do the trick but again you've got to consider voltage drop. sure the pump might work but you are lessening the life of the pump at a reduced voltage.