How do I hook up a 220 well pump to a generator?

Question

I have a well pump but no power other then my gas powered generator. I thought I could just put a heavy duty extention cord to the weel pump then plug it in, but the pump goes to 12PSI then turns off. After looking at it, someone told me that it is hooked up wrong.

My generator is a 4000 watt. It has several different types of outlets.

Answer 1

Here are a few things to examine:

1) What is the voltage of the generator? Hopefully it has a 220, 230, or 240 V single phase output. Any of the three should work fine for the well pump's motor.

2) Is the generator big enough? Compare the HP of the well pump to the generator's rating. One HP translates into roughly 750 watts. A 2 HP well pump will require power input of 1500 watts.

The biggest problem of operating motors with a small generator is the starting inrush of the motor. A typical motor can have inrush requirements of more than five times the running load.


3) How long is the extension cord? The longer the extension cord the more voltage drop from the generator to the pump motor. You want to keep this as short as possible. You also want the biggest wire size possible. The amps flowing through the cord create a voltage drop. This provides low voltage to the pump and can damage the motor.


I suspect you have a combination of #2 and #3. As the pump begins rising the water, the load increases on the motor. This increases the load on the generator as well as the amperage in the extension cord. The extra amps in the extension cord increases the voltage drop. Less voltage to the motor increases the current and you end up in a "death spiral" until the motor trips off.

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UPDATE (based on your question's "additional details")

A 4000 watt generator is a pretty good size. You stated that the well pump starts, but turns off at 12 psi. Since it starts, we know that motor inrush is not a problem. From a steady-state load perspective, a 4 kW generator can handle a 4 HP motor at full load. You didn't state the pump motor size, but for now we'll assume it is no larger than 4 HP.

At this point I would focus on the extension cord and other electrical connections between the generator and the pump. You want to have the shortest cables possible, and the largest wire size. Using a 100' extension cord when you only need to reach 25' adds extra resistance (and voltage drop) to the circuit.

Assuming unity power factor:
4000 watts @ 220 volts = 18 amps.

18 amps would require a minimum of 12 gauge. You may need 10 gauge or larger depending on the length of the cord.

Read the side of your extension cord. The conductor size (gauge) of the wiring should be stamped in the insulation. Please update your question with the extension cord conductor size and length.



Please feel free to send me an e-mail with additional details.

Good luck.

Answer 2

This Site Might Help You.

RE:
How do I hook up a 220 well pump to a generator?
I have a well pump but no power other then my gas powered generator. I thought I could just put a heavy duty extention cord to the weel pump then plug it in, but the pump goes to 12PSI then turns off. After looking at it, someone told me that it is hooked up wrong.

Answer 3

Generator For Well Pump

Answer 4

Don't forget that the amperage output of the generator at 240 volts is only half that at 120.

My 6500 Watt gas generator has a maximum current rating of 54 amps at 120 volts, and 27 amps at 240 volts.

My 120/240 volt receptacle and plug have 4 prongs, 2 hot, 1 neutral, and 1 ground.

Multiply the motor nameplate wattage by 2 1/2 to get the starting wattage load required.

Your extension cord should be rated for 30 amps.

Answer 5

What is the output of your Generator?
Your well pump will run, (barely), on 208 V.,
but not on 120V. which I suspect, is the output
to which you have connected it.
If the generator output has a plug with two parallel
slots this is probably the case.
(208 V. plugs have in line slots).

Answer 6

You have actually answered your own question. Jim W is correct in his answer. Connect the two hots and the ground to the green terminal. The only terminal that won't have a wire attached to it will be the "W" or white colored terminal. Good luck with the storm and may God bless.