Water Wells, Pumps and Generators!


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Old 09-06-14, 11:06 PM
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Water Wells, Pumps and Generators!

Hello guys!
I have a 1000ft well, pump is at 550ft. I am running a 3hp-10gpm-230V-Jacuzzi pump. Full load amp 17.1, the well is 200 feet from the elect service.
I know the pump start up will be more than 17.1 so what size generator can I pick up that will handle it comfortably?
I think a 5000 would do it but I would like your input please. I could be way off.
Thanks everyone!
Robert
 
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Old 09-07-14, 12:17 AM
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I could be way off.
And I suspect that you are. Electric motors will take three to six times their running amperes while starting. A centrifugal pump at that depth has a fair amount of "back pressure" on it that it has to get moving before it is actually pumping. That means a long starting period when it is "pulling" a heavy amperage load. I seriously doubt a 5kW generator will start that pump even if there are no other loads on the generator.

There is also the problem of rotational mass of the generator itself. I wouldn't be surprised that attempting to start that pump put such a heavy load on the generator as to cause it to stall the engine.

What I would do is to get a clamp-on ammeter and measure the actual starting amperage of the pump motor and time the duration until the amperage drops to the normal running amperage of about 17 amperes. You then need a generator with a surge capacity equal to or more than the pump starting surge. Even then I would want to try the generator before committing to buying it to be certain it will do the job.
 
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Old 09-07-14, 05:45 AM
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I have no experience with this information nor its accuracy.

Guidelines for using generators with submersible well pumps
 
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Old 09-07-14, 07:28 AM
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Make sure you look at the note at the bottom that states that the chart is for 3 phase motors and single phase motors require a generator with 50% more capacity.
 
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Old 09-07-14, 12:51 PM
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What is the LRA of the motor? That's what the generator has to be sized to.
 
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Old 09-08-14, 01:31 PM
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I've found LRA to be not very available but possibly I may be looking in all the wrong places. Do you have any suggestions? That would be real handy in situations like this.
 
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Old 09-14-14, 08:29 PM
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Thanks guys!
I will look into it more and run test. Not sure of the LRA that was not on the information I was provided. I have had the pump out one time to replace some pipe but did not look at it that well.
I will keep you posted.
Thanks again.
Robert
 
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Old 09-28-14, 12:02 PM
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OK guys here it is the start amps are 29 to 30. The motor only pulls this for less than 1 second and drops to 14 to 15 for run amps.

Thanks guys all help is appreciated. Have a great day!
 
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Old 09-28-14, 12:11 PM
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Just an FYI - 30 amps x 240 volts is 7200 watts or 7.2kw.
 
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Old 09-28-14, 12:17 PM
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Putting an instantaneous load of 7+ kilowatts on a 5 kilowatt generator is likely to immediately stall the engine.
 
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Old 09-28-14, 01:00 PM
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So what it looks like is I need at the min a 7500 watt gen........

Thanks!
 
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Old 09-28-14, 05:46 PM
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I would go with at least 10KVA so you can run a few extra loads. It's also bad to load a generator heavily for long periods of time.
 
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Old 09-28-14, 06:11 PM
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As you mentioned the 30amp draw at start up only lasts 1-2 seconds then drops down to 14-15 amps. That is 3600 watts.

If you plan to run other things other then the well, then maybe a 10KVA generator might be in order. Otherwise I would think a 7500 watt would do you fine.
 
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Old 09-28-14, 06:24 PM
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Thanks! I am looking at a 10 KVA and decided that was the way to go thanks to you guys (I would like to have a little more power than I need). I will only be using it in a small amount but the only time it will get hit hard is when the pump comes on and we don't use much water and I have a huge accumulator and a 300 gal tank for spare water.

We are trying to be more self sufficient out here on the plains with a wood burning stove and enough food and supplies to go months without service the water was the only issue due to the well depth. I can pump up 300 to 600 gal for storage in no time and shut the unit down and not need power for long periods of time.

I am also going to go with a propane gen because we have a 1000 gal propane tank that stays over 1/2 to 3/4 full all the time so that will give me a a gal per hr at 1/2 power....I think that's the way I added it up.

Getting as prepared as I can to be off the grid if the time comes.
Thanks everyone!
 
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Old 09-29-14, 07:16 PM
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If you're going to be off grid, I would recommend getting a liquid cooled generator that spins at 1800 rpms rather than the air cooled ones that run at 3600 rpms.
 
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Old 09-30-14, 06:52 PM
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Thanks again for all the great info! Working on it now. Winter for CO is just around the corner its snowing in the high country tonight a 2 hr drive away.
 
 

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