Irrigation Pump for Small Farm - Inverter Problems

[Sunking]

You have two big problems.

The rated running power is 2400 watts, not counting Start Up current referred to LRA which can be as much as 6 times FLA or running current. So your inverter is way undersized 6 x 2400 = 14,400 watts. Not say it wil take that much more like a 5 or 6 Kw inverter.

Second huge issue is you are running a TOY voltage of 12 volts, with way undersized batteries. Minimum Amp Hour Capacity @ 12 volts to run a 2500 watt inverter is 1700 AH at 12 volts or a 1200 pound battery. To maintain a 1200 pound battery takes a 1600 watt solar panel.

I would stick with the generator if I were you.

But if you insist on solar here is the minimum requirement to get the job done.

Inverter = 48 volt @ 5000 watts.
48 volt Battery Capacity = 400 Amp Hours
Panel Wattage = 1600 Watts
MPPT Charge Controller = 40 amps

Good luck.

[inetdog]

Thanks for any suggestions!

The 120 versus 240 is not the problem. It is the 12 volt part. 20 amps at 120 volts will be 200 amps at 12 volts. The starting current for the pump could be twice the nameplate current or more.
For 200A you should be using 2/0 or larger wire to the inverter and although 2 x #4 should be comparable, you will also have a lot of resistance in the terminations and connections. For the purpose of limiting voltage drop, you should be using 600kcmil wires. You may also just be drawing down the battery voltage.

Was the 13.6 measured at the inverter the load or no-load voltage?

For that amount of power, not only should you be using a larger inverter, you should be using a 48 volt (or at least 24 volt) battery bank and inverter.

[kjmclark]

Hello all,

We put in a irrigation pump for our small farm. The pump works fine, we can run it with our 4000w generator without problems (no grid-tie at the farm).

However, today I finally got our inverter connected, and it kept coming up with an overload error and shutting down.

So, some details. The pump is a Sta-Rite DS3HF - 1.5 HP centrifugal above-ground pump. Our well is very shallow, there's water at about 6' down. So the pump has no problem pumping it, as noted above, with adequate pressure and terrific flow rates for our purposes. The pump manual says it has a maximum current of 20 amps at 120v, 10 amps at 240v. We've been running it off our generator using 120v.

Our PV system is a single 240w panel going into a Tracer MPPT charge controller (yes, I know it could be better). The controller is charging our 4 deep cycle batteries in parallel, so our system is 12v. The batteries are connected together with 2/0 AWG interconnects. The batteries themselves are Tractor Supply Stowaway marine batteries, rated at about 100 amp-hrs and 700 cranking amps each (yes, I know not the best brand).

The inverter is a Cobra 2500w inverter (probably the biggest problem). It's connected to the batteries using Cobra 4 AWG cables, two pairs at 5' long. I connected the cables at the two middle batteries, so not perfect, but should get close to optimal current draw from the batteries.

My test runs were using a not-good-enough extension cord, 50' 14 gauge rated for 15 amps (yes, I know that's a problem, but I doubt it's *the* problem). When we use the generator, we use a 12 gauge, 5' power cord.

The pump *started* to shoot out water but the inverter very quickly indicated a low voltage fault, then changed it to a current overload fault and shut down.

So, I suspect my problems are: 1) too much in-rush current to the pump, 2) trying to run the pump on 120v, 3) trying to run the pump on a too-small consumer-grade inverter, 4) too small cable from inverter to pump (though a safety issue, not part of this problem, really), and 5) maybe too big a current draw from the batteries.

Going from least to most, I'm a little surprised that the inverter first says low voltage. The inverter said the voltage was 13.6v coming from the batteries. Would putting a starting battery in the mix help with this problem?

I'm going to hard-wire the pump to the barn before I'm done, so the not-good-enough cord shouldn't be a long-term issue. Besides, shouldn't that have limited the current draw at the inverter a smidge?

Would some kind of soft-starter help with 1 and 3? I've looked into this, but I want to be able to software-control the starter, and haven't found (yet, only been looking an hour) a soft starter for 120v, 20amps full load, that's 24v controllable.

Which leaves the 120v issue. This pump is selectable to run at 240, and the generator can produce 240 too. I was hoping to stick with 120v for various reasons, including cheaper inverters. Should I give up on that idea?

Thanks for any suggestions!