Well Pumps w/ Modified Sine Inverter

[inetdog]

I am not an expert, just a homeowner who's been doing this. So, with that disclaimer, here is my experience: we have been running a Grunfos well pump for six years. The first five of those, I was using my old Trace 2500 watt modified sine wave inverter. No problems. We now have upgraded our inverter to an Outback sine wave, though that had to do with our battery bank and nothing to do with the pump. No difference in operation of the pump that I can tell. For what it's worth.....

Depending on what model Grundfos pump you have, the motor may well be driven by a dedicated inverter that will accept a wide range of AC and DC voltages and so would not be affected at all by the waveform from your inverter.

[Terry1]

Running Grundfos SQ pump on modified sine wave

For about 5 years I used a Grundfos SQ 1/2 hp pump on an inexpnsive 120v modified sine wave inverter, with no problems. About a year ago I changed to a 3/4 hp SQ powered by a 240v modified sine wave inverter and deepened the pump into the well for more water. The original 1/2 hp pump was moved to another well and is still working. The new pump ran one season before it suddenly quit. Instead of the steady, 5 second long ramp up in current it now tries twice to start, gently with no more than 1 amp current, then takes a surge large enough to pull the supply DC voltage down below the inverter shutoff limit. Grundfos blames the pump failure on the modified sine wave inverter. I quote below -

The SQ and SQE pumps are designed to use AC power (electrical requirements shown below). Having said that, you can used DC power as long as you use an inverter to convert to 1x200-240V with a +6% and -10% tolerance as dictated by the requirements below. The problem I am seeing with your setup is the use of a modified sine wave inverter instead of a pure sine wave inverter. The modified sine wave causes problems due to its inherent current spikes as compared to the pure sine wave where the current alternates smoothly. This type of setup will likely cause excess heat buildup, potentially damaging the motor. I suspect this is why you are experiencing issues with the ramp-up, as it should be build current smoothly for the "soft start" feature of the SQ electronics.

Best,
Roberto Vidal
Grundfos Product Support

The 3/4 hp pump was out of warranty due to time limit anyway, so I'm looking for another pump .....

If this is for emergency use, get a generator. To rig up a solar PV system that has the capability to start and run a deep well pump, only for emergencies, is just - stupid.

It should be easy enough to store water for 48 hours, which should take care of most grid blackouts.

I don't know anyone who has run a large step up, 5,000w transformer off a mod sine inverter. (if you are there, speak up and help us out, inverter & transformer model #'s)

Running a 1/2 hp pump (1,000w measured load) is 84 amps DC, add another 20% for inverter losses, and another 20% for motor efficiency loss on mod-sine, and you need 1400 watts from the batteries, or 115 amps. 5x that to start the motor, at least (for 2 seconds). 12V batteries can't provide that much power. You car starter motor works fine at 8 or 9 volts, but the inverters shutoff at about 10.5V

Just letting you know what you are dealing with. This is a scale of power that most people don't work with at all, and it's not just scaling up a couple of flashlight batteries.

So if you have a limited budget, a genset that is large enough to start the pump (most 3,600 RPM brushless gensets @ 5KW should start a 1/2 hp pump) and a way to get gas out of your car, 2 gallons of gas will pump a lot of water, and you are all set.

A small 12V battery and a panel will give you light at night, but the scale needed to run a pump is very costly.

[Mike90250]

If this is for emergency use, get a generator. To rig up a solar PV system that has the capability to start and run a deep well pump, only for emergencies, is just - stupid.

It should be easy enough to store water for 48 hours, which should take care of most grid blackouts.

I don't know anyone who has run a large step up, 5,000w transformer off a mod sine inverter. (if you are there, speak up and help us out, inverter & transformer model #'s)

Running a 1/2 hp pump (1,000w measured load) is 84 amps DC, add another 20% for inverter losses, and another 20% for motor efficiency loss on mod-sine, and you need 1400 watts from the batteries, or 115 amps. 5x that to start the motor, at least (for 2 seconds). 12V batteries can't provide that much power. You car starter motor works fine at 8 or 9 volts, but the inverters shutoff at about 10.5V

Just letting you know what you are dealing with. This is a scale of power that most people don't work with at all, and it's not just scaling up a couple of flashlight batteries.

So if you have a limited budget, a genset that is large enough to start the pump (most 3,600 RPM brushless gensets @ 5KW should start a 1/2 hp pump) and a way to get gas out of your car, 2 gallons of gas will pump a lot of water, and you are all set.

A small 12V battery and a panel will give you light at night, but the scale needed to run a pump is very costly.

[Relic]

Options for a low-budget PV system

Great advice guys. Now this is just a thought, and I'd like to hear some opinions on it. I would like to keep my existing 230V pump to save money on the project. This is why I was thinking about using a 1:2 transformer to step up the inverter's voltage. Keep in mind, I am only wanting to use this as a backup/emergency system in the case of a grid failure.

If I purchased a pure sine inverter, could I use a large cap to help deliver the startup current to the pump? I also plan on using a large DC cap on the 12 volt side of the inverter to help out with startup. Also, do you think a 1500W continuous / 3000W surge inverter would do the job?

I do believe that I have the charging and battery storage capacity to do this. It's mainly the inverter that I am concerned about at this time.

Thanks again for the replies/advice.

[Mike90250]

More Power Scotty !!

You are going to have to increase your system voltage I think. A 1/2 hp pump with load, consumes about 1,000W, by the time everything is said and done (960W according to the metering on my XW6048, which takes into account power factor losses).
Starting currents are going to be at least 5x that, and a 12V battery & cables, will not deal well with that task. Your Step-Up transformer will have to be able to handle the peak starting power, or it will become the choke point.

And I suspect troubles with a mod-sine inverter, driving a high power transformer, because neither likes the other.

[SteveC]

I am not an expert, just a homeowner who's been doing this. So, with that disclaimer, here is my experience: we have been running a Grunfos well pump for six years. The first five of those, I was using my old Trace 2500 watt modified sine wave inverter. No problems. We now have upgraded our inverter to an Outback sine wave, though that had to do with our battery bank and nothing to do with the pump. No difference in operation of the pump that I can tell. For what it's worth.....

[Relic]

My solar powered well pump project, need advice!

I'm in the planning stages of my solar-powered submersive well pump. I've chosen my solar panel, 163W, charge controller, batteries. Now I am trying to decide what type of inverter will do the job. I plan on using a 3000W / 6000W peak inverter. I have either a 1/2 or 3/4 HP pump, not exactly sure. The output is about 5 GPM. I plan on using a 1:2 stepup transformer to achieve the 230VAC needed for my pump. This also gives me the option of also using the 12VDC and 115VAC.

My main concern is which type of inverter to purchase...modified or pure sine wave. I have read conflicting information regarding the use of modified sine wave on well pumps. However I am on an extremely tight budget, which makes the modified sine inverters more appealing to me. Another question, could I build my own filtering circuit on the AC side of the inverter to smooth out the modified sine wave? (i.e. a series inductor, X cap, and current limiting resistor). If that is possible, does anyone know what component values I would need to achieve adequate filtering, while keeping the sine wave in phase?

Any advice would be appreciated. I have worked on this plan for a long time now. This is the main road block I have reached, picking the right inverter. Also, our research website has a blog topic on this very subject and may be useful to some. Here's the link - http://planetxresearch.wordpress.com...ions/#comments

Thanks in advance for any help/advice and feel free to leave comments in our blog! Take care all.

[Mike90250]

Without knowing your needs ( x GPM @ y Lift ) I can't comment.

I think simpler is better, a generic 240VAC pump costs a lot less than the fancy DC vari-speed w/ $$$ control box. But you need a $$$ inverter to run the 240VAC pump

[ecusolar]

Wow, that was fast Mike, thanks a lot.

Yeah, the pump makes such a difference.

I was locking for German pumps, I like the Lorentz, it comes with charger inverter and LPD.

They work with 24V and 48V as I was reading, maybe that would be a good take instead of the 110V pump.

I post the specs. http://www.lorentz.de/en/products/su...mps/ps150.html

Please let me know what are your thoughts on that one.

Maybe I should add that this will be financed from the Goverment as an experiment, if all works fine and is inside of budget they might purchase thousands of this system.

We are awaiting heavy weather problems, it almost didn't rain and the hydros are with few water. Farmers will be in big **** if we can't solve this problem and they grow our food.

[Mike90250]

In good weather, you could get 6 hours of sun, and pump while the sun is out. You really need to measure how much power the pump is actually using, you can even use a DC ampmeter on the power line for the inverter, and calculate, if you can't get the killowatt on it.

Generally, assume 500W per 1/4 hp. My 1/2 hp pulls 1,000 w from the inverter.

I would install at least 700W of PV per each 1/4 hp. Your best power production will only be for 2 hours an hour -+ each side of noon (or wherever your panels aim point is. As the sun moves, your power will decrease and increase. If your batteries get low later in the day and the inverter shuts off, you need more PV. You might consider a tracker array, more complex, but more even power flow. forget about trying to run off batteries, pumps consume way too much power.

Choosing the RIGHT PUMP is critical. I have a 1/2 hp pump, gives 9 GPM at 160' For your 50' or so, you should get 20 gpm for 1/2 hp. Look for the proper pump and motor combo for your application.

[ecusolar]

Irrigation pump system

We are with the plan to install an irrigation solar system in one of our properties that have lemon trees, it's about two hectars.
The well has plenty water in 16 meter deep (48 feet about).
We want to use the true sine xantrex sw2000 inverter/charger and two 150 AH batteries as a buffer.http://www.xantrex.com/power-product...m-sw-2000.aspx

The 110V double wire pump should work 6 hours and give 5 to 7 gal per minute, we think about a 1'2 HP submersible pump.
I do have in another well a 1/2 HP pump and connected a KillaWatt, it reads about 900W and starts very soft and fast, it has a fusebox but no condensers in it.

The system should only work during producing sunlight (6 to 7 hours daily) with some kind of timer.

The purpose is just to try it out, if all goes fine we wnt to size it up for larger extentions.

Can someone help me out if that would be OK? What would be the array size with all the thermal loss?

I was reading most of this thread but got only about 60%, lol.

Thanks in advance

Joe

[LucMan]

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...

http://www.terrylove.com/forums/show...bmersible-pump

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.

[SteveC]

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.

[Sunking]

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...

http://www.terrylove.com/forums/show...bmersible-pump

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.

[Mike90250]

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)

http://www.terrylove.com/forums/showthread.php?20711-Questions-on-deep-well-submersible-pump