Your load could be (maginally) handled by a #10 wire in terms of not
overheating the wire and insulation. So that means you need to size the
wire for voltage drop. A quick calc (assuming 2 wire circuit) says that
#10 copper will give you slightly over 10% voltage drop out at the well
head, #8 gives 6% drop, #6 would give you 4% drop. If this is an extreme
service unit (running for weeks on end during the summer when the grid
supply voltage is sagging), go with the heavier wire.

Karl Townsend wrote:
You may remember I asked about the pressure switch wire for my pump last
week...

The group convinced me to replace all the wires and put in conduit. More
investigation shows I should move the pump control box to near the pressure
switch at the same time, in the basement.

Anyway, I now will have a 380 foot run from the basement to the well with 2"
conduit installed. The pump uses three wires with loads as follows: red
wire - 27.5 amps, black wire - 19.1 amps, yellow wire 10.8 amps. I learned I
need THWN wire last week. What wire sizes should I order?

Karl