run water pump 3/4 hp 115/230 13/6.5 amps 60 cycle ac only, what size generator(watts), have to run 230volts,

This is a reasonable question and I'm glad to help you.

First, the generator rating: One hp is equivalent to 746 watts, so at full load you'll be pulling 560 watts. Your generator capacity should be at least double that for a long-term, reliable installation. You might get away with 1 kW for a short time, but I would go for a 2.5 or 3 kW generator because you also have a major current surge to deal with a motor startup.

Re 230 VAC, I agree this is the better choice for a run of 500 feet.

Re your wire size, good practice -- and maybe your local code as well -- requires that the line drop between source and load not exceed 3% of the operating voltage, or 6.9 volts. At 6.5 amps the total resistance that would generate a drop of 6.9 volts is R = E/I = 1.06 ohms. You want less than 1.06 ohms in 1000 ft (down and back). According to CRC tables AWG #10 solid copper is rated at 0.97 ohms/1000 feet, so #10 will be OK here.

If you need to limit your line drop to 2%, use #8. In no case should you try to get away with #12. If you have to wire up the system at 115 VAC, you will need to go down to #6.

This will not be the best answer. I believe you have two questions here. You have a 3/4 hp motor that will draw 13Amp on 115 volts at 60 Hearts or Cycles and that can be also wired by changing the way it is hooked up to draw 6.5 Amps at 230 volts on 60 Cycles. Other Question is about wire size concerning voltage drop over 500 feet of distance. Check out Ohm's law Though it should not be used for general a.c. motor and transformer circuits or a circuit containing any e.m.f or voltage other than the impressed voltage. (re all ref. - Practical Fundamental of Electricity.)

One mile of copper wire a Quarter of and inch diameter offers about 1 ohm resistance. . You need to also question how many wires you need to run in your cable; whether it is one white one black and one green safety ground or all the former and a red besides . Be aware that the smaller the number of the wire, the larger the size of the wire; that a number six wire is much thicker than a number 16 and that the former offers less resistance. Getting an electrician to put all of these facts together and hook up your water pump will keep you in good stead with your insurance company even if you know how to do the job yourself as well as keep you from burning out your motor.

At 230 V, your water pump will draw 6.5 A at rated output power (0.75 hp).

The generator, of course, should be at least 0.75 hp x 0.746 kW/hp = 0.56 kW, but it will actually need to be a fair bit larger. Here's the details:

Your water pump motor has a starting current that is probably 6 times the rated continuous current, so Istart = 6 x 6.5 = 39 Amps.

Most generators can put out about 4 times rated current for short periods to support motor starting. Basically, you don't want to make the generator try to put out more, if you can configure the system properly. This makes the required continuous generator current approx. 10 A. At 240 V, this corresponds to 2.4 kW.

My recommendation is to use a generator no smaller than 2.4 kW (2.5 kVA if they give this rating as well) at 240 V.

Next, when choosing the wire to make the 500 ft run, you will need to calculate voltage drop so that the motor has enough voltage at its terminals. For this, use the starting current (39 A) estimated above. Motor terminal voltage during starting needs to be not less than 80% of motor rated voltage (230 V) for you to be fairly sure that it will get up to speed without problems.

Vmotor, starting = Vgen - Istart * |Zwire|

Note that the generator voltage, Vgen = 240 V (single phase).

But the motor nominal voltage is 230V (single phase). This difference gives you some voltage drop margin at the outset.

Wire impedance magnitude, |Zwire|, is both resistance and reactance.

For a 10 AWG wire, R ~ 1.0 Ohm/ 1000 ft, and X/R ~ 1

So, if you used a 10 AWG circuit, on a 1000 ft round trip, |Zwire| ~ 1.4 Ohms

So, the voltage at the motor terminals during starting is approx.:

Vmotor,start = 240 - 39 * 1.4 = 185.4 V

This corresponds to: 80.61% of 230 V

During running, the motor voltage is:

Vmotor, run = 240 - 6.5 * 1.4 = 230.9 V

This is golden!

If the motor starting current is significantly higher (you can tell from the information on the nameplate), you will need to use a larger wire and rerun the calculations.

If you move the generator closer to the pump, the smallest wire size you are allowed to use is 14 AWG, and protect it with a 15 Amp breaker. The larger 10 AWG wire must be protected with no larger than a 30 Amp breaker, but you will need to check that the motor has its own overload protection.

You can run the water pump with a 500 watt portable generator,3/4 Hp = .75(746)= 249.5 watts. but a bigger unit , say 5000 watts would be preferred at least you'll have excess power for other loads like lights and other appliances. Also the pump will need more power during start-up. At 300% of 6.3amperes=18.9 amperesWatts required =230(20)=4600 watts. Generator Rating =5000 watts.

A No.10 AWG copper insulated wire type TW will be sufficient to handle 6.5 amperes at 220 volts. Voltage drop would be IZ=6.3(1.8)2= 5.7volts, impedance for #10 copper wire is 1.8 per1000ft. 3% voltage drop of 230 Volts=6.6volts.Hence, 5.7 volts is good enough.

3 4 Hp Water Pump

The steady state solution is for the generator to supply 1500 watts. The generator will have to have a surge rating higher than this to handle the startup current. This is an unusual application since water pumps usually only run on demand to restore water pressure and not continuously.

3/4 HP will move a tremendous amount of water, is this a community well? If it is just for your house, a 1/4 HP pump is better suited. If the lift is exceptionally high, say 200 feet, then 1/2 HP will reduce the number of stages required.

If you figure your daily water consumption, you may find that the best efficiency would be to pump water once a day to a storage tank than can maintain the pressure. This would allow you to share the generator for other purposes.

3 4 Hp Well Pump

6.5 A. @ 240V. = 1560VA.

Starting current will run about 13A.

You want a 2KVA. Unit that can handle a 3KVA. surge.

When a motor is the only load, the starting current of

the motor is the factor that sizes the generator.

Even though your load is only 6.5A., if you're running

a 500' distance, voltage drop is a factor.

Because there's a start current involved, I'd use

#8 AWG. Cu. minimum.

The 13/6.5 amps and the 230 volts are the two bits of data needed to do the calculation, but I don't understand the "divided by" sign in between the 13 and the 6.5. Is it 13 amps or 6.5 amps or 2 amps (literally 13 divided by 6.5)

The conversion of Amps to Watts is governed by the equation Watts = Amps x Volts

For example 1 amp * 110 volts = 110 watts

volts X amps = 1495 watts consumption so a generator that will produce no less than 1500 watts under full load.