240 Volt Wiring Help Requested

My project entails a 500 foot, 240 volt underground circuit from the meter pole to a pump well pit five feet deep. The 1 h.p. jet pump will have 15 feet head pressure applied and will run on demand to water cattle. Estimated continuous pump time would rarely exceed one hour. There is a ground at the meter pole and I plan to have one at the pump end also. We have not purchased wire nor supply end circuit breakers yet (pump motor has thermal protection). This amateur would appreciate your help and comments on any plus to using 4 conductor wire for the run and letting the center tap float. The rural power comes down the meter pole, inside conduit and through the meter and out the bottom to the main switch box (I don"t think this that is a overload circuit breaker), then back up the pole inside another conduit and spans to the house and a 100 amp circuit breaker box inside. I would like to put the circuit breakers for the pump inside the switch box with the main breaker and then out the bottom of it and go underground. Motor specifications call for GFCI. Have done this with 120v but not with with 240v. Thanks for your help in selecting wire size and other specs. I will follow up on any on-line links to other information or charts

500 ft ya need to calculate voltage drop
so what is the amp rating off of the pump motor nameplate

We really need nameplate rating of pump. However, a 1 HP motor at 230 V should pull 8 amps. For safety sake lets say 15 amps and #6 copper should be fine. A GFI breaker is pretty similar to hook up whether it is 120 or 240 volt. If it was me I would put the panel in the well pit so I could put an outlet and maybe a light in it. If so I would trench in a 2/2/4/6 URD which can be gotten at almost any electrical wholesaler. Since it is 500 feet away from power it would stand to reason on somed cold dark night the darn thing will have problems. Run a cable with 2 hots, a neutral(grounded), and a grounding wire, and drive a ground rod at the pit(they are cheap, rod and clamp maybe $15).

I have been retired for a while so take this information at what you paid for it. According to the code book I have (not the latest) the amp load on a 1hp motor is 8 amps at 230 volts. Then you mult by 1.25 to get 10 amps for you full load current. 500 feet of 12/2 uf w grd. has a vd of 7 volts. This is the cheap way of doing it.

You dont say if you want to run in pvc or direct burial, either will work. In the future if you ever want to add anything out by your pump you may want to go with the bigger wire and a neutral. Greg may has the better system. My motto was always "Do it once and do it right and be done with it."

We learned the hard way. 15hp irrigation pump would go out about every 4 years with the owner. I took over and last year the pump went out again. They had #6 Aluminum. They never checked the amps. I put a new pump in and checked the amps. Should pull 72 amps. It was pulling 168 amps. Changed the wire to a O copper and the amps came down. Could have use a smaller wire, but that was all I could find local. Was about 70'

Sorry, I had intended to include in my original post that copper wire is called out in motor specs and the amperes requirement with 240 v is 6.5.

I think you would really kick yourself if you did not run 4 wire and provide yourself a 120v outlet out there. I think you would be kicking yourself dozens of times over the next years.....

Paul