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Retrofit my well pump to solar?

Bill Ding Homes

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Dec 13, 2022
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I have a 2hp, 10.2a 1500watt ac well pump installed. I would like to retrofit it to run on solar but I have couple of questions. Static water level is 60ft and pump is set at 135 ft.

1. Could i just create its own mini-grid with 2000w of panels and a 3kw all in one?
2. RPS makes a retrofit system but its more expensive than a new pump and panels, controller, ect.. on their same site.

I am going totally off grid, but my setup will be strained by the well pump i am afraid.
 
I put our well pump on solar power.
1hp pump, down about 40ft. in the casing.
Uses about 8A when running.
Fills an 80 gallon pre-charge tank.
It is important to find out the LRA (Locked Rotor Amps) for the pump,
so the inverter can be sized to be able to start the pump.
LRA for my pump is 41A, for example.
 
I doubt a HF 3kw inverter would start and operate a 2hp well pump. No reason to use an AIO if there is no grid. A LF inverter/charger/ATS for generator pass through would be a better bet. Your battery bank could be charged through a dedicated MPPT SCC. Depending on how much you pump and how often will determine the PV needed and battery storage.
 
I have a 2hp, 10.2a 1500watt ac well pump installed. I would like to retrofit it to run on solar but I have couple of questions. Static water level is 60ft and pump is set at 135 ft.

1. Could i just create its own mini-grid with 2000w of panels and a 3kw all in one?
2. RPS makes a retrofit system but its more expensive than a new pump and panels, controller, ect.. on their same site.

I am going totally off grid, but my setup will be strained by the well pump i am afraid.

Stuff isn't adding up.

2hp = ~1500W, but pumps can use notably more than they output. 10.2A * 120V = 1224W, so this is likely a 230V pump.

Most pump motors have a big surge typically 5X the run current. Exceptions are the Grundfos SQ line as they have a soft start built in. Your power source needs to be capable of a 50A true surge at 230V. I emphasize true because many AiO HF inverters have negligible surge capability even though they claim 2X continuous.

This beasty can definitely handle it:

 
Stuff isn't adding up.

2hp = ~1500W, but pumps can use notably more than they output. 10.2A * 120V = 1224W, so this is likely a 230V pump.

Most pump motors have a big surge typically 5X the run current. Exceptions are the Grundfos SQ line as they have a soft start built in. Your power source needs to be capable of a 50A true surge at 230V. I emphasize true because many AiO HF inverters have negligible surge capability even though they claim 2X continuous.

This beasty can definitely handle it:

I am running a grundfos 2HP pump depth 360' , runs at about 2.9Kw/ surge is around 12K with a signeer M6048D (true low frequency) all in one. no problem at all. i have 4.8Kw of panels. this inverter is usually stocked in cali @1899. <https://www.sigineer.com/product/60...-off-grid-hybrid-80a-mppt-charger-etl-listed/>
 
1) I'm wondering if you really need a 2hp pump.

2) Consider a Grundfos SQ pump (several threads already on/with them). Could be the lowest cost option when everything else is factored in.
 
There are pretty ordinary 0.5 HP pumps that can do over 80 m (app 250 ft.) pressure. Question is how much water (l/hour) do you need. I'm pretty sure Grundfos SQ (2,5-2 for instance but US models might be different) will do at least similar pressure on 2000W panels (if required). There are also "solar pump inverters", Grundfos (as mentioned above) as well as other makes, that connect PV panels directly to a "normal" AC pump and have VFD/slow start. If you go that way, the 2 HP pump will be too big for the available PV capacity though.
 
Yeah I think the biggest recommendation would be a smaller pump. Drillers usually throw in bigger pumps than you need (sometimes its what they need to move that is in their truck) or sometimes just cause they like to drop it all the way to the bottom of the well even when the static is higher. I always install all my own and in a decent producing well I only set 15-30 feet below the static water level and try to size the pump to be roughly at the rate of the well recharge. I'd think about what GPM you really need at any one second during the day and then get a pump of horsepower that can do just that... and maybe a little more to grow into. Call a company that does solar pumps and see what they say. I bet even a half horsepower or a three inch pump might be plenty if you aren't needing fire sprinklers or something huge. Good luck!
 
Lots of variable in this problem - and don't forget that a decent 1500-2500 storage tank may seriously offset the high flow rate issue.
Even a low volume 1 gal a minute pump running 24 hrs per day is ~1500 gal.

Then a small household pressure pump, and you may not really need the high flow deep well setup.

Sun doesn't shine at night, so likewise a larger battery bank can extend the run time - possibly for 24 hours per day.
 
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