Anyone running small 3" submersible DC pump for offgrid? Concerns about performance

fastline

Solar Enthusiast
I will first say I am very familiar with wells, pumps, and electric, but I have never tried this little tangent. We are doing a quick and cheap cabin. Minimal is the game here to get inspectors to fly it. I am looking to enter the dwelling with a 24V charge controller and PV, and have a small lead acid battery back for storage and inrush currents. I am looking to run a small 3" DC pump either on 24V or we could have to go to 48V if I cannot find joy in this design.

The issue is the pump will have a 300ft distance, including the pump drop. I have determined that we will need about 100ft of head. The actual flowrate is really not a big deal because it will be coupled to a 30gal pressure tank and estimated water need is about 10-20gpd. I'd be happy with 1gpm but the key is getting enough pressure. Plumbing code requires a min of 15psi water pressure and I am accounting for that with the 100ft of head requirement.

The issue is as one could guess, we have some decent voltage drop going to that pump! I am also not yet sure if the pump will really serve the need with the voltage drop and pushing a small pump near max lift. The batteries will certainly be able to deliver the amps but that will get pinched down with a smallish wire set. I am really trying to get this done on 12ga wire! Everything is stupid expensive right now.

I see lots of you guys running pump inverters and such but I am just looking to control the pump with a complete DC system and a pressure switch. Or other very simple approach you guys may know of.
 

fhorst

making mistakes so you don't have to...
Most simple : boost converter to up your voltage.

They aren't expensive.
300ft, that's +1500 watt pump?
You lose a lot less with higher voltages (48v system)

In Thailand there aren't any regulations.
Absolutely not for the filling speed of a water tank!

If it can do 300ft, 100 should be easy and have enough pressure.
Voltage is easy to fix, +60A on awg12... That's rated for 20A.

With 48v (you probably can get away with it.
24v, probably not.

I'm guessing for the watts.
My 350ft 3 phase (AC) pump does 2500w at start, 2000 when running
DC is more efficient for pumps, so I guessed it should be about 1500 watt
 

fastline

Solar Enthusiast
I realize now I did not explain well. 300ft total wire distance. I am accounting for the vertical distance in the well from surface to pump in that. Actual static water is at 30ft.

I do realize higher voltage solves all of this, and something I will do right after the "officials" leave. Actually I will ditch the DC pump entirely and install my inverter and 240V pump....lmao....

I just need to get signed off by the code guy and they will never bless all my lithium batteries and such. Just don't even want to deal with them. I live in a county that hates the people that pay them....
 

fhorst

making mistakes so you don't have to...
Is a booster (step up) against the regulations?

It's totally normal as "they" (grid company) uses this all the time to keep the voltage high enough.

I lived in a country where there where more rules then people...
And understand your pain.
 

Wellbuilt

Solar Addict
the difference between 12 and 10g is .20 a foot for pump cable with black heavy duty plastic cover
I just paid .95 a foot for 10 2 with ground @ 700’ there was a 130 dollar difference in price .
It was delivered last week .
 

fhorst

making mistakes so you don't have to...
I'm getting lost with your numbers there, just curious if you got it working now.

You have a pressure tank that is supposed to deliver the 15psi water pressure that the inspector needs, correct?

You have 115L pressure tank, so you probably want to use it, even as the water usage is as low as just 75L a day

Toilet and shower probably takes more for one person...
Lol.

Well .. we reuse all our waist water, so the amount we use isn't that important.
Out Thai type washing machine uses +80L on a single wash..
(Only cool water) lol.

Anyways..
Back to regulations..

A cabin needs apparently 15psi.
And you insist that the submerged pump should deliver enough pressure to have all 75 liter of usage at 15 PSI?

I'm confused.
Why use pressure at all?
You could just have it without pressure, and install normal pump from the "normal" tank to give you the needed 15 PSI.

Most households I know that have their own water have a 500L or more water tank, and use a small pump to deliver the water pressure for the house.

Only reverse osmosis filtration use pressure tank, and that tank is obviously not pressurised with the well pump...

But you do live in a crazy country...

Water pressure requirements for off grid cabin...
Lol. Next thing is regulating the wild animals where to sh!t..

Is it still allowed to use a hand pump?
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