Please help if you are able

derekbettingerderekbettinger Registered Users Posts: 3
I need help I am trying to run a 220 volt 2 and 1/2 horsepower water pump off of solar only I have no source of electricity at the site any help would be greatly appreciated. Thank you


  • PhotowhitPhotowhit Solar Expert Posts: 5,727 ✭✭✭✭✭
    Short term, even long term if it's not a daily thing. It will be cheaper to run a generator.

    If it's a daily thing please describe better you needs, length of time, when you need it to run...etc.

    There are different systems for different needs, A big solar array and battery bank and inverter would be one solution. for some thing.

    For watering a field, it might be better to replace the pump and run a direct solar pump, we'll need the depth of the well and amount of delivery, for this solution as well.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former, 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.BB. Super Moderators, Administrators Posts: 32,315 admin
    Welcome to the forum Derek,

    I will give the suggested solution to all things solar/battery powered... Conservation and picking the most energy efficient device you can--Almost always cheaper to conserve electricity than to generate it.

    There are some very nice smaller pumps from Grundfos and others that are very "solar friendly". Some operate from 120/240 VAC at ~900 Watts and no starting surge current (around 1 HP), and there are versions that will take power directly from multiple sources (solar panels, higher voltage battery banks, and even AC power from mains/generators/inverters--Same pump). That is the Grundfos SQFlex series.

    Our host has a variety of solar capable water pumps (and feel free to call them for sales and engineering support--Our forum here is based on volunteers answering questions):

    Of course you have to match the well specifications (depth of water, well GPM rating, run dry protection, etc.) as needed...

    Now that I have got that out of my system... Lets say you know more about wells and pumps than I do (very easy). And that you have sized your needs and matched it to the pump's specifications.

    The easiest solution at this time (as far as I know--Again, I am not in the solar/water pumping business) is to pick a 3 phase inverter rated for use with a Variable Frequency Drive.

    More or less, you connect the power source (solar panels, battery bank, genset, etc.) to the appropriately rated VFD, connect the VFD output to your 3 phase motor. Program the VFD for your motor power curve/other needs (some can be setup for constant pressure/variable  pumping, etc.). 

    A VFD is a variable frequency AC inverter... It is programmed (usually) to start the motor at a low frequency, and "slowly" bring the motor up to its set point RPM.

    Also, a "solar capable" VFD can monitor the input power available from the solar array and run the pump at a slower RPM in the early morning/late afternoons. I.e., vary the pump RPM to match the available solar energy.

    Using a 3 phase motor takes care of starting issues (no capacitors) as 3 phase pumps "naturally" have a rotating field (vs single phase induction motors which need a starting capacitor/switch to create a rotating field).

    There are lots of issues and options out there (and you have to find a knowledgeable source for solar powered VFDs--If that is what you are looking for).

    There are other alternatives too... "Slow pumping" from a well to a tank/holding pond. Then using a surface pump to supply 60 PSI for a cabin/home.

    To give you an idea of what was out there in 2012, is an article from India about solar+vfd:

    Here is an example (again from 2012) on what a 2.2 kWatt solar VFD can look like (no idea if company is still in business--Link to give you an idea what to look for):

    Some more VFD pumping general information:

    There are a lot of details that need to be addressed--And if you can find a local to your (southern Nevada?) that knows VFDs, motors, and pumps--That would be great.

    Sorry for the older links... Don't get too many questions for larger water pumping systems here.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • derekbettingerderekbettinger Registered Users Posts: 3
    Thanks for the welcome,glad to receive such a prompt response with an immense deal of information.Thank you. I'm going to explain exactly what I have going on! A friend of mine died 2 days ago, natural causes and he left his outdoor weed farm to his daughters, someone broke into a smallbuilding and took all irragation parts , solar panels, batteries, generators but left the 220v 2 1/2 hp water pump and the plants, I was called to try and save it from dying,All I know so far is this:
    -they have a 220v 2.5HP water pump
    -pump needs to be run for 12 hours a day constant
    - absolutely no grid power near farm
    -would like to do it all around best way
    An I got to say thank you again so much for everything you have shared, ive never tried to join a forum before, thanks again for being so welcoming. If you could provide any suggestions  regarding the details I provided, or if you could tell me what else I need to find out, I would so greatly appreciate it an I know these girls father would as well. Thank you.
  • BB.BB. Super Moderators, Administrators Posts: 32,315 admin
    I am so sorry about your friend and his daughters.

    To your needs... First thing is to save the crop and you should buy/rent a generator and get the pump up and running. Quick and relatively inexpensive first step.

    Renting/borrowing a generator can help let you figure out what your power needs will be. You will need to look at the pump and confirm that it is a 240 VAC single phase pump or possibly a 208 or 240 VAC 3 phase pump.

    Besides water pumping, will your need power for other things (home, workshop, fans for drying, lighting, etc.)?

    What fuel will be available? Diesel, gasoline, propane?

    Is there any electrical service panel(s) left that give you an idea of what size genset/other loads are used/needed?

    And, frankly, figure out the cost of short/long term solutions (genset, fuel, plus solar) vs the value of the crop.

    Just to take a guess and do an example here. Say running a 5 kWatt genset, gasoline, and the pump takes 2.5 HP (probably takes less, but you would need to measure the loading). You don't want to oversize the genset, that can be a big waste of fuel. A standard gasoline genset is most efficient/best used around 50% to 80% of rated load. If you get an inverter-generator (such as a Honda euXXXX family, they can run fairly efficiently down to 25% of rated load--A standard genset uses about the same amount of fuel/Gallons per Hour at 50% of rated load of rated load). The genset also needs to be large enough to start the pump (starting surge).

    Taking a guess that the genset will use around 1 GPH for every 4,000 Watts of load, a genset running a 2.5 HP pump 12 hours per day would be (assuming 70% electric motor efficiency):
    • 2.5 HP * 746 Watts per HP * 1/0.70 efficiency = 2,665 Watts running load
    • 2,664 Watts * 12 hours per day = 31,968 WH per day (= 32. kWH per day)
    • 31,968 WH per day / 4,000 WH per gallon (gasoline genset rough efficiency) = 7.992 gallons of gas per day
    • 7.992 gallons per day * $3.00 per gallon = $23.98 per day
    The above numbers are pure guesses, and if the water pump is not operating at 100% load but only 50%, the fuel usage will be less.

    Generator pricing will be all over the map, to very inexpensive generators that may cost less than $1,000 (inexpensive 7 kWatt genset from Costco) to something like a $5,000 7 kWatt Honda eu7000i inverter-generator (quieter, more fuel efficient at lower loads).

    If you assume that a good gasoline genset will run for 2,000 hours, at 12 hours per day that is:
    • 2,000 hours / 12 hours per day = 167 Days (less than 1/2 a year)
    If you go diesel--Price is all over the place (not cheap to very expensive). As an example, random diesel genset from Amazon:

    ~$4,000, runs around 30 hours on 12 gallons of diesel at 50% load (5,000 Watt rated, 2,500 Watts is 1/2 load):
    • 2,500 Watts * 32.4 hours * 1/12 gallon tank = 6,750 WH (6.8 kW) per gallon of diesel
    • 32,000 WH per day load (2.5 HP pump) / 6,750 WH per gallon = 4.74 gallons of diesel per day
    • 4.74 gallons per day diesel * $3.50 per gallon = $16.59 per day (diesel
    So better fuel efficiency for diesel... The above is a very noisy generator (no sound insulation--I guess). And diesels tend to be more efficient than gasoline/propane gensets at lighter loading (less than 50% of rated output, fuel flow will decrease due to inherent efficiencies of Diesel engines).

    I have not gotten into the solar side of things... Solar driving a 2.5 HP pump will be expensive, very very expensive.

    Any idea of what size of solar power system was installed? Just the solar panels alone would be on the order of (for a full offgrid solar power system with AC inverter, battery bank, etc.). Fixed array facing south, optimized for summer usage, Las Vegas NV area:

    Las Vegas
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 69° angle:
    (Optimal summer settings)


    • 32,000 WH per day * 1/0.52 off grid system efficiency * 1/6.07 hours of sun (October) = 10,138 Watts of solar panels minimum
    • 10,138 Watts of panels / 250 Watt solar panel = ~41 relatively large panels mounted to racking/etc.
    If they pulled the solar panels, inverter, battery bank out of a shed, and the panels were not rack mounted--Then your friend was probably running just a genset and did not use solar (at this time), or had a much smaller solar system just to run some LED lighting, cell phone, laptop, etc. stuff in the shed/building at night...

    I know that this is a solar forum, but I doubt that off grid Solar would be cost effective in the short term--And would be difficult to order/install/bring online in the few days needed to save the present crop.

    Finding the "right size" of diesel genset to run your pump--Just looking at United Rentals (Las Vegas NV):
    15.2-23.2kW Towable Generator, Tier 4 Diesel Compliant
    • Mounted to a highway-legal towable trailer
    • 19-29kVA actual power capacity
    • Tier 4 compliant diesel engine
    • Power up tools, equipment or light towers
    • Add this towable generator to your cart now
    This mobile generator delivers reliable, clean power in an innovative, easy-to-use towable unit. Designed for long run times, features include a voltage selector switch and programmable settings. Enclosures are encapsulated for sound-attenuation and manufactured of rust-proof aluminum with a durable, industrial powder-coated finish for maximum service life. It meets or exceeds EPA Tier 4 diesel regulations for increased efficiency and safety.
    You are viewing equipment rates for Las Vegas, NV
    "Smaller" diesels are not that easy to find... So you may end up with a larger unit which will not be cheap to buy or rent.

    I will stop here... So many questions and pure guesses above. Your thoughts/corrections/etc.?

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • derekbettingerderekbettinger Registered Users Posts: 3
    this is the pump that needs to be ran in the very near future and it needs to be run off 100% solar . I am being told that they cant use a generator On site or even close to site panels were on a rack in being told . all that was left was the pump. I have permission to use generator for 2 weeks to maintain crops but needs to be off site in 2 weeks. An looking at pump I see its only 1 1/2 hp . sorry about telling you the wrong info.
  • BB.BB. Super Moderators, Administrators Posts: 32,315 admin
    If they are in California... Yeah, the state is very very anti generator.

    You might call the well drilling company and see if they have any records about the solar power system.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,511 ✭✭✭✭✭
    I live in the emerald triangle in Northern Calif, and it's really the wild west out here.   Shooting, missing persons and unclaimed bodies all over. 
    There are 3 types - the original organic mom & pop growers,
    the new professionals with their permits and winston-salem money and dirt free fingernails ,
     the Cartel growers from mexico which set up tresspass grows anywhere they can.

     The work crews of the later 2 are underpaid, hungry and will murder and rob any one, and that's who likely stole the gear.  If you do not attend the site 24/7, it WILL be cleaned out again.   What county does not allow a generator, or is it a landlord request ?

    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | 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 ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    gen: ,

  • BB.BB. Super Moderators, Administrators Posts: 32,315 admin
    It is possible that the owner of the land has a 2 week limit... But (assuming this is in) California has setup a pretty complex regulation matrix for generators (heavy trucks, "portable" industrial equipment, etc.). Here is a FAQ that attempts to put out the framework:

    It was getting to the point, for example (my very rough understanding), if you went to buy a part for your forklift, the parts store was asking for your name, address, equipment type/model, and serial number(s) just to buy the part.

    And that data was sent to the state--If your equipment was not already registered and regulated, it would be now.

    Much of the laws/regulations that "allow" generators only applies to "backup generators" of relatively small size.

    In this case, it would be prime power source for water pumping--Probably a much "different" animal (for California).

    Note that many of these requirements can be based on the rules for local "districts"--So what is allowed in XYZ air district may not be allowed elsewhere.

    The state is attempting to control sources of air (and other?) pollution sources (getting rid of old/dirty tech and replacing with new tech diesels, limiting the use of any pollution source, etc.).

    Sort of similar to what happened to over the road trucks and basically outlawing (rather than grandfathering) older/dirtier diesel trucks (owners would have to move trucks out of state/down to Mexico, etc.).

    -Bill "I certainly may be wrong on the details" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 32,315 admin

    I will attempt to roughly size your system... This is a big enough system that you may want to find a local installer/engineer to design/install/configure your system. This is not a small project.

    If this in the Sierra Nevada Range (central California), Dave Angelini is local and could possibly help. From his signature:

    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
    E-mail [email protected]

    A very quick sizing for a 1.5 HP pumping system (summer months, no winter pumping?) off grid solar power system. Assuming pumping during day, just enough battery bank for 1 day of "cloudy weather pumping".

    Well pumps can be "very difficult loads" for solar power systems. Less expensive pumps have high starting surge power and need a large(r) inverter and battery bank to support those starting loads. There are "better" pumps out there that are more efficient and have almost no starting surge such as the Grundfos SQFlex line (take ~900 Watts to run and ~900 Watts to start). And why I suggested you contact the Well Company to see if they have information on this well installation.

    Assuming worst case:
    • 1.5 HP * 746 Watts per HP * 1/0.70 efficiency = 21,599 Watts running load
    • 1,599 Watts * 12 hours per day = 19,188 WH per day (= 19.2 kWH per day)
    • 1.5 HP * 746 Watts * 5x starting load = 5,585 VA starting load
    So, as a first guess, a 4,000 Watt AC @ 48 volt DC input inverter would be a good start.

    To calculate the battery bank size--Two methods. One based on starting load (large battery bank for high starting loads). And a second based on energy storage for 1 days pumping. Assuming flooded cell lead acid battery bank (cheap/rugged/3-5 year life minimum):
    • 4,000 Watt inverter * 1/1,000 Watts per 100 AH @ 48 volt battery bank = 400 AH @ 48 volt battery bank
    And based on 1 day's storage and 50% maximum discharge (for longer battery life):
    • 19,188 WH per day * 1/0.85 AC inverter eff * 1 day storage * 1/0.50 max discharge = 941 AH @ 48 volt battery bank
    Neither of these battery banks are "small"... If you only need to pump for a few hours when the sun is not shining (early morning/late evening), perhaps you can get away with 400 AH @ 48 volts... That would be
    • 4x 6 volts @ 200 AH "golf cart" batteries in series = 48 volts @ 200 AH
    • 2x parallel strings of GC batteries = 48 volts @ 400 AH
    • 4 series * 2 parallel = 8 "Golf Cart" batteries total
    Then there is sizing the charging of the system... Again two calculations. Nominally, suggest 10%-13% rate of charge minimum for a full time off grid system. A second calculation based on location and hours of sun per day.
    • 400 AH * 29.0 volts charging * 1/0.77 solar panel+charge controller derating * 0.10 rate of charge = 1,506 Watt array minimum
    • 400 AH * 29.0 volts charging * 1/0.77 solar panel+charge controller derating * 0.13 rate of charge = 1,958 Watt array better
    Then there is based on energy used and hours per day of sun... Need your location for that, but a quick estimate for an array tilted 20 degrees from horizontal (summer harvest) facing south for Mariposa California (assuming clear access to sun from at least 9am to 3pm--Any shading/trees/mountains that block sun will seriously reduce your harvest): (forget the last two columns--Not of interest here)
    MonthSolar Radiation
    ( kWh / m2 / day )
    AC Energy
    ( kWh )
    ( $ )
    Annual5.971,601$ 250

    If we assume 6.0 hours of sun per day, that will carry from Mid-March to Mid-October:
    • 19,188 WH per day * 1/0.52 off grid AC system eff * 1/6.0 hours of sun per day (summer) = 6,150 Watt array minimum
    So, that is not a small array. And ideally, you would only assume to use 50% to 65% of daily predicted harvest for a "base load" (load that needs to be run all the time), or:
    • 6,150 Watt array / 0.65 base load fudge factor = 9,462 Watt array nominal
    Say you get some MPPT solar charge controllers to run at 80 Amp charging current:
    • 9,462 Watt array * 0.77 panel+controller deraings * 1/58 volts charging * 1/80 amp charge controller = 1.6 = 2 MPPT charge controllers.
    Midnite makes a nice controller that could work well here... You want to limit the charging current to the battery bank (400 AH battery bank, around 40-80 Amp charging current max) and the Midnite family supports a current shunt to the battery bank to allow the controller(s) to manage charging current to the battery (the rest runs your pump).

    Now--This is a very rough guess--And your decisions (how much and when to pump, perhaps splitting into two arrays, one facing south west and the other south east to get "more hours of charging time for battery bank", etc.) will affect the system design greatly...

    Contacting Dave or another installer is going to be a big help. (I am sure that Dave is "cringing" at my calculations and assumptions here)

    Also, our host, Northern Arizona Wind & Sun can work with you and engineer/ship a system to you based on your needs:

    Just take the above as an example of the basic questions and how a system is designed... I do not have near enough information to know if this is about right/overkill/or even not enough.

    Good luck,
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,511 ✭✭✭✭✭
    To size your pump, you also need to know the lift from the well. and pressure needed at the outlet along with the flow rate.
     in my case, I have a 1/2 hp pump, at 165Ft lift and 8gpm.  I can run it during sunny hours (9:30am - 4:30pm) off a 3Kw PV array and a 350ah 48V battery (my old original configuration with L-16's )  I'm using a 6kw inverter, but I think a 4kw would work for my case (I also have 95F daytime temps the inverter has to work in w/out shutting down from thermal overload)
     You need your irrigation data (pressure and flow) Loss thru any filtering and pump flow curves and power requirements

    3 phase motors are more efficient than single (1) phase, but they also require 3 phase power, or a proper VFD motor controller.
     And it's all moot, if you don't have site security with a couple people camping there 24/7 to keep an eye on things
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | 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 ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    gen: ,

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