Looking for advice with new motor and pump for my specific needs?

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CMO

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Hello,
I am seeking some advice from some of the professionals here…
I have a 6” well that is 580’ deep with a static water level of 300’. The well report stated 40GPM production rate. The 100 gallon pressure tank at the top of the well is approximately 20’ above my house and approx. 150- 200’ away, which is supplied to the house with a 1-1/2” pvc water line.

I had a 3HP - 3phase FRANKLIN “234316” series motor paired with a Subdrive 150 that lasted 15 years and was very manageable with regard to in rush current / SFA and RLA.

I am off grid, so THE MOST IMPORTANT FACTOR TO ME is the SOFT START CAPABILITY in order to keep the current as low as possible.
I am open to installing a 1000- 3000gallon cistern water storage tank at the top of the well in order to help mitigate the high current used by the deep set pump.

The current drop pipe is 1-1/4” schedule 120 PVC and the supply has been great until the pump and drive failed. The house is a double master BR type that has separate jacuzzi tubs and doorless walk in showers with 3 heads.
The other 1-1/2 bathrooms are standard type.

I have calculated the Maximum in-rush current of a single phase 3HP motor to be between 45 amps at 240v, which is far too high for my current inverter and generator power set up.

The previous Subdrive 150 and 3HP motor used between 2000-4000 watts. I would prefer to keep the total current draw whether it be in-rush current or the SFA ratings at or below the total 23amp current draw previously used by the Subdrive 150 & 3HP pump.

My subdrive is still working and operational and I would also be comfortable using a VFD if required in the future. I am also thinking of separating the well electrical circuit from the house circuit and running them separately in order to control and mitigate the effects of the substantial load that the well requires…

Is there a way to reliably get a single phase 3HP pump to consistently soft start with a current draw and total power consumption that would be similar to the 3phase / 3HP pump that is controlled by the VFD / Subdrive?

If I were to use the same 3HP / 3phase pump and simply power it up at 50-60Hz for 30- 60 mins / 1-2x per day in order to fill a 1000 - 3000 gallon storage tank, would that help to extend the the life of the pump, while still maintaining the flexibility and high flow output capabilities of the 3HP pump? Maintaining the ability to use with a pressure tank type of system until I can add a storage tank? While most importantly continuing to maintain the low in rush current and total power consumption < 5000 watts?

I am open to advice and suggestions as there are so many different choices and options available… for now I am thinking of installing another 3 phase pump with a storage tank and separating the well power circuit from the houses, in order to allow the new pump to simply run openly at 85-100% to fill the tank, rather than having to 200 additional feet of water line as well as pumping against the pressure tank.
This would also limit the pump to < 1 or 2 power cycles per day…

I really started out thinking that I wanted and needed to simplify the system by converting to a single phase motor but most of the single phase options that I am aware of will require a substantial compromise or loss of flexibility/ capability in either flow or output capability, the total in-rush current / amperage draw, and total cycles per day…

I recognize my situation is unique, which is the reason I want to retain as much flexibility and redundancy as possible with the pump that I choose. I have spent hours and hours studying pump curves, design tables and the AIM MANUALS for Franklin, Grundfos and Goulds.

I am seeking the advice of any Pro’s here that understand all the variables and characteristics that I have described as they are specific to my system, who may be able to help me improve upon my system in any way possible…

Recommendations for motor and pump manufacturers, sizes, specific design types,
# of phases, specific models, etc.
Any advice would be greatly welcomed and appreciated!

Thank you for your help, I appreciate your time and consideration.

C.
 

Valveman

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Congratulations on having the longest lasting Subdrive I have heard of to date. But I am sorry you live in a state where power is not reliable and you have to make your own. It is so much easier and less expensive to have power capable of a little in rush current.

Locked rotor amps of a 3HP single phase is actually about 71 amps. Even a 1HP needs 40 amps in rush to start. The Subdrive is a VFD, which is why it is able to reduce the in rush current.

Using a cistern is a good idea because that would allow you to use a smaller pump in the well with lower in rush current. I would use a 1.5HP model 10SQ15-330 in the well and a 3/4HP model 10SQ07-240 in the cistern. The SQ pumps have a soft start built in without needing the VFD. You can just control the well pump with a simple float switch. Then the pump in the cistern can be controlled with a PK1A kit, that will deliver the same strong constant pressure without needing a VFD.

This will cut the total HP from 3HP to 2.25HP. It will also reduce the inrush current greatly by starting a 1.5HP instead of a 3HP. If you want to continue to be able to get water at 40/60 pressure directly from the well you will need to keep a 3HP size pump. Then adding a cistern and booster pump will increase the total HP by at least 3/4HP. It would be best for in rush current to spilt the 3HP load up and have two smaller pumps.

The 200' to the house only adds some friction loss at flow, and doesn't push back on anything.
 
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Fitter30

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3 ph is the only way to keep the in rush amps down. Using a pressure switch or a level control for a storage tank can use a aftermarket vfd. Want to vary the speed by water pressure a transducer would be needed. Turning single phase into 3 phase. Use a 7.5 hp vfd and a NEMA 4 enclosure if in a harsh environment.
 
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CMO

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Thank you for the prompt reply and Excellent advice! I really appreciate the input.
I am definitely going to add a storage tank to split the pumping loads as well as to be able to separate the entire electrical circuit for the well pumps, from the loads at the house. This should limit the total cycles of the deep set pump as well as maintain the low in-rush and total amperage current of the pump that I need, while also transferring the majority of pumping cycles to the pump in the tank, that is above ground and easier to maintain.

Can solid state electronic type soft starters be used with single phase pumps or integrated into the control boxes? Also, I have been told that using a submersible pump mounted inside the storage tank would be better and last longer than using a jet or booster type pump… I haven’t heard of that before but am definitely open to it. The pressure and storage tanks will be +20’ in elevation above the point of use and the 200’ of supply line is 1-1/2” pvc from the pressure tank to the house which is then plumbed with standard 3/4 & 1/2 pex.

As I mentioned before, I know there are many options and ways of getting the water that I need. I am just hoping to optimize my system in a way that balances flexibility and capability with cost and reliability by choosing the equipment that best fulfills my specific needs while maintaining as much resiliency as possible.

I will look into the recommendations that you listed. Thank you again for your time and consideration. I appreciate your thoughts and advice.
 

Reach4

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If this is for a house, rather than some farming operation, with irrigation or stock, the Grundfos 5SQ15-450 would have more than enough power.
No storage tank needed for either. With a storage tank, I might go for the 5SQ10-360 or 5SQ10-410 down the hole.

10SQ15-330 I think would have enough lift, and could deliver more gpm.


These SQ pumps will be a softer start than the common 4 inch pumps. But if using a 4-inch pump, a 5 gpm 1hp may be enough to fill your cistern tank.

There are other pumps that can work directly from solar cells. They cost a lot more.

If you use one of these in your 6 inch well, I would strongly recommend a flow inducer. If you want info on construction, let us know.
 

Valveman

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Figuring a total head of 515' (400' water level and 50 PSI) the 3HP only delivers about 12 GPM. With no pressure pumping into a cistern a 1.5HP can do 12 GPM from 400' deep.
 
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