Well Pumps w/ Modified Sine Inverter

Starting is not the main issue, it is running for extended period of time. Motors run hot with MSW which wears the windings in the motors out and synchronized AC motors will not work at all.

My situation is this:

-I am building a spec house that will (most likely) eventually be hooked to the grid. The house is finished on the outside and sheetrock is painted on the inside and I am ready to start trimming windows and building kitchen counters/cabinets and installing interior doors.

- Well has been drilled and piping between well & house is installed.

- plumbing is roughed in.

I would like to install a submersible pump Now that I can run on my solar PV system that will also be suitable for running from the grid.

I guess I can have a dedicated pure-sine wave inverter for the submersible, but was wondering if there are pumps the will work with mod-sine wave?

I think the run is too far to go with a 12 volt pump.

Many power tools have "brushed" " universal" AC/DC motors, and don't have starting capacitors. they don't care about sine/mod sine.

Most AC well pumps have induction (AC only) motors, and starting capacitor, and run capacitor.

If your water is only 15' down, you can use a surface pump, they can suck water to about 20' before they cavitate. And after the pump, it's easy to push the water up. But, that does not get you water pressure in your house, you need a pressure tank, or a 30' high tower to hold water.

I am definitely going with a submersible. I would have to put a shallow well pump in the house (to protect from freezing) and that would be a lift of 30'.

Also, I have already installed the pitless adapter and backfilled the 1" 160 PSI waterline and some 12-2 UF. The drilled well is 160 feet deep with 10 GPM, so I will be putting the pump down at least 100' below grade.

this link is telling me I can use a mod. sine inverter with a 2K peak and 970 continuous watts to power a 0.5 HP submersible pump.



I think I might just get a 1/2 HP 115 VAC submersible and try it with my existing 1250/2500 watt mod-sine wave inverter.

$0.05 says the pump inverter combo won't last a month.

I'm running a 1/2 hp pump with 160' lift, 7gpm, and it pulls 1,002 w off my pure sine inverter @ 240VAC. (see .sig pump model) Mod sine will take 20% more power, so that's going to be 1200w cont, motor run 20% hotter, and a 2KW peak won't start a 1000w motor which needs 5-10x start power, over run power. My inverter has 12KW surge. I'm not sure wholesalesolar has reliable info posted in their table.

Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV
Powerfab poletop PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 400A battery bank | 15, Evergreen ESA 205 fa3 "12V" PV | Midnight ePanel |

PS-
I went with a conventional well pump, not the $2000 solar pump

Thanks for the info. I may have to rethink the idea. I really have no need for water right now as I still have lots of work on the spec house before someone is living there. It would just be nice to have the water hooked up so potential buyers could at least see the toilets flush.

My total head is only 30 feet though so maybe I could get by with a smaller pump?

You need to get with a competent plumber / well person.

1) a surface mount pump can suck water up, about 20' max. You could hook one up to your well pipe, and if the static level does not drop too much, you could slowly pump (even 1 gpm is oodles of water) Just because your well is 100' deep, doesn't mean you have to put the pump way down there.

2) surface mount pump can pump as high above the pump, as it's limits are, even while sucking from 15' below ground.

3) you need some sort of storage container, pressure tank or something to limit the pump cycle time.

Thanks Mike, but as I will eventually be connected to the grid, I am resisting the temptation to use a suction pump. Submersibles seem to be the standard for deep well pumps in my area and the realtors tell me that buyers are often scared off by shallow well pumps. I will be using a standard pressure tank also. The only non-standard thing I am considering is using a 115 VAC submersible (instead of a 230 VAC) so I have the option of using a small generator for grid outages.

So far I have done EVERYTHING on this house (except the foundation) including cutting the hole through the well casing and installing the pitless adapter. While I am not a competant plumber, I still have plumbed up three complete houses and a bunch of smaller jobs. I have installed several deep well pumps and yarded a few back up out of the well to get them repaired/replaced. I may not be fast, but I consider myself half-fast.

Also, keep in mind that everyone in my town is running off a well since there is NO town water. In the old days everyone had springs or shallow wells but now-a-days, the perception is that shallow wells will run dry in times of drought but deep wells don't. People see those little pump houses and they see problems and they get scared off.

Just last week, I upgraded my inverter from a Trace 2500 w. 12. mod. sine wave to an Outback pure sine wave.

That being said, the Trace has been in 24/7 use running our household for 20+ years. There has never been an issue with anything, appliances, motors, electronics, including computers.

We have a Grunfos 120 v. soft-start well pump which provides our water, the head is about 100 ft. This is a 5 gpm model. The pump has been in operation for almost five years, no problem from the Trace mod sine wave inverter.

[We upgraded to the Outback because we needed a more user-adjustable inverter for some new batteries we have on order, or the Trace would still be in use.]

We only pump the well water during sunlight hours, the water going into a cistern from which we pump into the house with a Dankoff 12 v. Flowlite pump. So the Grunfos is not in round-the-clock use.

But we have never had an issue with the mod. sine wave inverter. The only one we've used is the Trace, so I cannot speak to any others.

the old skinny wire theory to softstart pumps

thanks for the info steve!

Found this interesting tidbit about well submersible pumps:

According to Franklin, using the longest length of the smallest wire possible will give you a natural soft start from a standard pump. In other words, if you use 400' of #12 wire with a standard pump, it will result in about a 20% reduction in starting current and about a 36% reduction in starting torque.

Here is the whole thread discussing off-grid well pumps...

Very interesting stuff about pumps surfaceing here in this discussion.

I'd advice caution about using too much small gauge wire to emualte a soft start, as you may risk the pump never getting up to speed where it switches from the start winding to the run winding, and burns up. Be sure you use the pump MFG's wire table for this, not just any wire table

the link to the pump forum is good too (good enough to repeat)

This is really bad advice. Ac motors are constant power devices. So if you lower the voltage it demands more current. More current means more power losses and hotter running motors which burn up faster.

That's right, you don't want to be intentionally running a motor at decreased voltage like that. I do recommend a soft-start pump, however. In our case, the regular version of our model of Grunfos had a starting surge of 60 amps, or so the pump co. from which I was buying told me. The soft-start version of the same pump draws an 11 amp start surge. 60 amps is at or above the surge limit of some inverters.

The retail price to us of the soft start model was $100 higher than the regular model, and I was ok with that.

By the way, I had to insist on a soft-start model. The sellers kept trying to talk me into saving the hundred bucks. They were not that experienced with off-grid systems.

Electric motors today have +/- 10% design voltage rating, it's never a good idea to exceed these limits.
208/230 volt motors= 187/253v
120v=108 to 132 v
Motors running out of these ranges will have a shortened lifespan.