HP to watts question to power submersible with generator

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SteveMitty79

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After getting so much stuff caught up on the farm, I'm just about ready to get my 2HP submersible installed in my well. The water line is 180 feet. It will sit at 260 feet.

I know that a HP is equal to 746 watts, and theoretically it would take 1500 watts to drive 2 HP. That just seems way underpowered to me. Or is my logic flawed?

So, right or wrong, taking into account the 260' column of water in a 1-1/4" pipe, what power generator would I need and how should I take start-up draw into consideration since there is no power data with the pump (it's a cheapo Chinese and they're probably clueless)?
 

Reach4

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It takes a lot more than that. The HP ratings are mechanical power. The pump is not nearly 100% efficient. A pump takes much more power during starting than to run. That will vary from pump to pump even for a 2 HP designation. Generators differ in how they are able to handle a starting load. If this is a pump that will be generator-driven a lot, you might choose a pump that is better at that.

There have been past posts on how much generator was needed for a particular pump, but I don't have specifics for you. Here are a couple threads:

https://terrylove.com/forums/index.php?threads/generator-size-for-submersible-pump.54227/
https://terrylove.com/forums/index.php?threads/generators-and-well-pumps.55572/
 

Valveman

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Volts times amps equals watts. A 2HP sub draws 12 amps at 240 volt, which would make it about 2800 watts. But it may take 6 times that much to start it. You might start a 2HP with about an 8000W gen set, but it may take a little more.
 

SteveMitty79

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I appreciate the replies. So I guess I'll have to do a bit more homework and maybe upsize my prospective generator surge capacity a bit more. What I currently have just won't do it. Is six times startup draw realistic? That's about 18KW surge. I was hoping someone had experience checking the startup amperage on 2HP pumps and could give me a good guess-timation.
 

SteveMitty79

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Ok, I read those threads. A bit technical sometimes, but this is what I gathered for my situation: I have a 230VAC 2HP pump I will set at 260'. It is a three wire with a control box and capacitor, which I understand is a plus for me. I also have that entire run in 12ga wire, which I understand smaller wire acts as a soft start effect? A plus I guess. And, it will not be hooked up to a pressure system. It's for top-filling tanks and totes. I read somewhere that these conditions my put the start up draw close to the running amperage. Is that true? If so, how does that effect my generator requirements? Thanks.

As an edit, I have a Honda ES3500. It's an old generator but in excellent condition. It weighs over a hundred pound, maybe 150. I bought it from a guy who used it for powering his race car trailer. He took good care of it. It has a hertz meter and adjustment. That's Greek to me. Electric start. One 33A 115V breaker and one 16A 230V breaker, the latter I need. I read somewhere the heavy flywheels are less prone to bogging down and I believe if anything this has one as it's a tank.

So, would I do any damage trying to run my pump setup on this thing to establish a baseline and maybe enough to get a startup current draw meter reading on it?
 
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VAWellDriller

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Ok, I read those threads. A bit technical sometimes, but this is what I gathered for my situation: I have a 230VAC 2HP pump I will set at 260'. It is a three wire with a control box and capacitor, which I understand is a plus for me. I also have that entire run in 12ga wire, which I understand smaller wire acts as a soft start effect? A plus I guess. And, it will not be hooked up to a pressure system. It's for top-filling tanks and totes. I read somewhere that these conditions my put the start up draw close to the running amperage. Is that true? If so, how does that effect my generator requirements? Thanks.

As an edit, I have a Honda ES3500. It's an old generator but in excellent condition. It weighs over a hundred pound, maybe 150. I bought it from a guy who used it for powering his race car trailer. He took good care of it. It has a hertz meter and adjustment. That's Greek to me. Electric start. One 33A 115V breaker and one 16A 230V breaker, the latter I need. I read somewhere the heavy flywheels are less prone to bogging down and I believe if anything this has one as it's a tank.

So, would I do any damage trying to run my pump setup on this thing to establish a baseline and maybe enough to get a startup current draw meter reading on it?

You should get a baseline startup current reading with line power.... readings will be all out of whack probably on an undersized generator because the voltage will drop. I doubt you'd hurt the pump to try it once with the Honda, but give it a few seconds and if it doesn't start unplug it.....I doubt it will work. I have a small generic, 4000/6600 run/surge in the pump truck that will start a 2HP, but it doesn't like it very much. I wouldn't do it to the pump or generator all the time, but as an emergency thing every now and then I don't think it will do much harm. I think you'd be ok with a 5500/8000 which is a pretty common generator wattage.
 

SteveMitty79

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You should get a baseline startup current reading with line power.

Forgot to mention, we are off-grid, powered off solar and propane and gas generators.

I wonder if I should just rent a big honking generator and meter the start up with that? That should be accurate enough to size a genny. Or I guess I could buy the 5500/8000 or a bit larger and try that, if the return policy at Lowe's and HD allows, barring a fail.

Any recommendations for makes and models in that power range?
 

Reach4

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Forgot to mention, we are off-grid, powered off solar and propane and gas generators.
Take a look at SQFlex. https://us.grundfos.com/products/find-product/sqflex.html for off-grid wind or solar.

If you are doing solar, you would probably be much better off with a smaller pump sized to pump from 260 ft but from the expected low water level.

On the other hand, for a generator where you are visiting the well to turn on the generator, I can see why you would want to get that over with.
 

VAWellDriller

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Why do you need such a big pump... most off grid folks go don't have extravagant water needs. A smaller pump probably cheaper in the long run that buying and fueling a new generator.
 

SteveMitty79

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Why do you need such a big pump... most off grid folks go don't have extravagant water needs. A smaller pump probably cheaper in the long run that buying and fueling a new generator.

I installed a Simple Pump with electric motor option that worked great for years, but we recently outgrew it with the addition/expansion of infrastructure and animals. The output is only 3/4 gpm but when running a lot, was sufficient. Now, I want to be able to fill up tanks and totes quickly and use the Simple Pump as emergency backup.
 

Valveman

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I have a Honda 3500 that will barely start a 1.5HP test pump. The #12 wire will help. Starting the pump against a closed valve will help, but don't leave it closed for more than a minute. It won't hurt to try it but I think you will need a 5000W gen or so.
 

SteveMitty79

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I have a Honda 3500 that will barely start a 1.5HP test pump. The #12 wire will help. Starting the pump against a closed valve will help, but don't leave it closed for more than a minute. It won't hurt to try it but I think you will need a 5000W gen or so.

I'm looking at some Briggss and Stratton generators on Craigslist that are 5550/8550 watts. Seems to be several of the same models sold some years ago during an ice storm that folks are dumping at the same time. You know, used once or twice and sitting with bad gas the whole time in the garage.

Anyway, my setup with terminate at a utility hydrant. It's 1-1/4" inlet and outlet, no pressure. Would it be better to have the hydrant opened/no pressure or closed/building pressure at startup, when you say starting the pump against a closed valve will help?
 
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