Off grid cabin build: 115 vs 230 volt submersible pump?

Re: Off grid cabin build: 115 vs 230 volt submersible pump?

Another thing to consider is what you have for an inverter. If it has 220 volt output available than go with a 220 volt pump. If you only have 115 volt inverter, then you will require a step up transformer with the expense and losses that go with it.
One of the most important things to consider is a 2 wire + ground pump, or a 3 wire + ground pump. The 3 wire models have an external starter box with Capacitor start, far easier (less surge) to get started than the 2 wire units, regardless if 115 or 230 volt units.
Most off the shelf 1/2 hp sub pumps will top out at roughly 100 PSI at the pump outlet. The water will naturally find its way up the pipe to the level of the water in the well, regardless of how far down the pump is. If for example the water level is 100 feet down, it will require roughly 50 PSI just to get the water to ground surface. In that case, the total max the example pump could provide after getting the water to the surface, would be less that another 50 PSI, for a total of 100 PSI at the outlet of the pump. But to be safe, in this example, plan on no more than 30 PSI at the well head - - - if indeed the water level is 100 feet down.
There are other models of these standard, off the shelf sub pumps that pump only 5 GPM instead of the "normal" 10 GPM, and the lower output pump produces higher pressures. It has more, but smaller impellers than the standard model, thus lower flow but higher pressure.
These are centrifugal pumps, so unlike positive displacement pumps, they don't work harder at higher pressures, in fact higher pressures are easier on them because they don't move as much water. Think of your mother's vacuum cleaner, you plug the inlet or the outlet, and the motor speeds up because of reduced loading, less air or no air is being moved.
And of course you could also consider the Grundfoss. Expensive, but depending on your situation, could be worth it.

Re: Off grid cabin build: 115 vs 230 volt submersible pump?

If the pump would be the only 240v item i would vote for 110v pump. Instead of tranformer spend a bit more on thicker cable. I would think the cable would be cheaper upfront and in the long run as wire would tend to have a much longer life than a transformer. If you had longer runs transformer could win out.

I have a 1hp well pump 330ft on 10awg wire. 110v. I bought 110v as can be powered from my backup inverters as well as my main. Wire cost about 160 dollars. And easier to find a generator that supply 110v in a pinch. I would have gone with smaller than 1hp but that was what i had on hand.

But having a autotransformer could be useful to future system expansion.

Re: Off grid cabin build: 115 vs 230 volt submersible pump?

I understand what your saying. But for my situation it works. My points are valid and my be worth consideration. Although it wastes copper in transmission of power it saves transformer cost. But you do need a power source that kind supply peak current. I know 8 awg in my case would be more appropriate. My 1hp pump is using. Roughly 750watts based on trimetric. Less than 7amps over 330ft 4.7 % voltage drop.

Re: Off grid cabin build: 115 vs 230 volt submersible pump?

I would have bought a .5hp in my case if readily available as i am pumping water just 20ft down. It was either the 1 hp or the 1.5hp. I am in mexico and selection were i was, was a bit limited.
I was suprised myself at how close the pump was to using 746.

Re: Off grid cabin build: 115 vs 230 volt submersible pump?

There is also the power factor of the motor, and all the system losses. My XW inverter logs my 1/2 hp pump, at about 1,000 watts. It pumps to an elevated holding tank and runs 1x a day for about 3 hours. I am well within the spec'd lift/volume curve for my pump.