Bimodal system to run Deep well

I'm sure this has come up many times but i have yet to get a good answer. I am new to off grid systems and i have a client who wants a bimodal syste or complete off grid system to power his 1Hp 240v Single phase deep well and freezer in case of grid outage. I have come up with him needing about a 2.2kw system but taking the LRA into consideration it may end up being like a 6kw system. The pump is already been set and i dont know the exact LRA for that particular pump but the "ugly book" syas for a 1HP 230v pump the LRA is 48A. We have toyed with the idea of installing a start compacitor bank to negate the LRA so we can keep the Solar system down to a small size. Does anyone have any experience with this or have any ideas?

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Bimodal system to run Deep well

    Does this well pump have the start capacitor at the top of the well (vs inside the motor down the well)?

    If so, you may want to research using a VFD (Variable Frequency Drive) for the well pump. Basically, these are poly phase AC inverters that start with a low frequency to get the well motor up to speed--i.e., soft start. (typically used with 3 phase pumps, but also pumps with an external capacitor start lead).

    You can also use a VFD to run the motor at less than full RPM--to better match pumping capacity to well/piping/GPM requirements.

    I think I have read here of people using a 4kW inverter for 1 hp pumps.

    Magnum makes a nice ~4kW inverter/charger true sine wave with native 120/240 VAC split phase output.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Bimodal system to run Deep well
    JOSI wrote: »
    I'm sure this has come up many times but i have yet to get a good answer. I am new to off grid systems and i have a client who wants a bimodal syste or complete off grid system to power his 1Hp 240v Single phase deep well and freezer in case of grid outage. I have come up with him needing about a 2.2kw system but taking the LRA into consideration it may end up being like a 6kw system. The pump is already been set and i dont know the exact LRA for that particular pump but the "ugly book" syas for a 1HP 230v pump the LRA is 48A. We have toyed with the idea of installing a start compacitor bank to negate the LRA so we can keep the Solar system down to a small size. Does anyone have any experience with this or have any ideas?

    Yes.
    How often are the power outages and how long do they last?
    Buy a generator.
    Spending $8,000 on a solar power system to accommodate occasional outages is foolish.

    For what it's worth, I power a 1/3 HP water pump from my system. It has to be controlled to come on only when the sun is shining and the batteries are full because it uses so much power. I also have a 1 HP 240 VAC septic/digester pump which must be used under the same conditions. It has a soft-start built in, but still sucks down 1,200+ Watts. Fortunately it runs less than a minute per day.

    The main use of my system is to keep the refrigerator going. That's 1,200 Watt hours per day right there. A freezer can actually stay cold on its own for at least a day, providing it isn't opened.

    In your case you are dealing with a lot of unknowns, especially in respect to how long the pump and freezer (another big power user) will run. If you had a good estimate on that you could work out how big a battery bank would be required to supply those needs for however long the estimated power outage would be (or for a day and assume solar/gen recharge). Even so, I doubt 2kW of array would be in it much less 6kW. Mine should be a tad larger than the 700 Watts it is, but then I do more with it (it runs everything including the computer & satellite modem).

    On the whole, a battery-based power system for temporary outages is not worth the investment. The batteries will die over time regardless, which makes them largely a waste of money. If they do need/want this ability it's worth looking into the grid-tie possibilities in the area so that a hybrid system could be installed. Better return on the capital expenditure.
  • JOSI
    JOSI Registered Users Posts: 11
    Re: Bimodal system to run Deep well

    We dont have much power outage. Thats why i suggest a bimodal system that way at least he can offset some of his home power and the system wouldnt be just sitting there. The freezer is 115v 5a. I have an interactive off grid work sheet. I plan on having a 48v 800ah batttery bank. Like was said in previous post the freezer wont run much at all. I am just worried about the LRA on the pump. The pump does not have a start compacitor on top.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Bimodal system to run Deep well

    Before investing a lot of money in solar invest in a meter that can capture the actual start-up demand of the pump. You will need this for sizing the inverter that has to power it and the battery bank size to back it up. Don't guess; measure. It helps avoid those ugly surprises and expensive outlays.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Bimodal system to run Deep well

    Additionally, the Power Factor of your pump motor, will influence the inverter size. My 1/2 hp pump, indicates 1,000 watts on the inverter control pane when it is running. I agree with Cariboocoot buy a meter and measure the critter.
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • JOSI
    JOSI Registered Users Posts: 11
    Re: Bimodal system to run Deep well

    Ok i got a meter that recorded the High, low, and average amps of the pump. The high was 14amps and while it was running it was at 4 to 5 amps. The homeowner finally admitted he didnt know if it was a 1 HP pump or not. I can handle any grid tied system but these off grid is kicking my but. Looks like i will be signing up for an off-grid class very soon!!!!
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Bimodal system to run Deep well

    It could still be a 1 HP pump, but just not having to work very hard. That's the trouble with pumps: the power required is not a simple function of HP = Watts. It depends on how much resistance the motor encounters trying to start against a column of water under pressure and then push more water to it. The greater need for lift, flow, or pressure = greater power required.

    Yes, off-grid designs are a bit more difficult than straight forward grid-tie - sometimes. Not always. :D
  • JOSI
    JOSI Registered Users Posts: 11
    Re: Bimodal system to run Deep well

    This is what i came up with:

    (1) Midnite Solar MNESTSGVFX3524CL150 Pre-Wired System
    (15) MAGE 250w solar panels 3 in series 5 string in parallel
    800Ah battery bank

    The pump had a 14amp starting surge and the Outback GVFX3524 had a surge rating of 6000VA which is 6000w. So 6000w divided by 240v is 25amps. So if i did it right the Outback Inverter/charger can withstand a 25amp surge.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Bimodal system to run Deep well
    JOSI wrote: »
    This is what i came up with:

    (1) Midnite Solar MNESTSGVFX3524CL150 Pre-Wired System
    (15) MAGE 250w solar panels 3 in series 5 string in parallel
    800Ah battery bank

    The pump had a 14amp starting surge and the Outback GVFX3524 had a surge rating of 6000VA which is 6000w. So 6000w divided by 240v is 25amps. So if i did it right the Outback Inverter/charger can withstand a 25amp surge.

    There is no question that the VFX3524 can handle this: I use one of those inverters and it works for everything. In fact, 3500 Volt Amps (not exactly the same as Watts, btw) is 14.5 Amps @ 240 VAC. The power factor of the motor comes in to play if you were talking about Watts, but as you have an actual current measurement this should not be a problem.

    Be sure to use "full size" wires on the battery: that 3500 VA output is 146 Amps DC, plus the inverter's requirement. You should probably use 2/0 wire on this or larger. Make sure you have the RTS for the charge controller and the MATE for programming the inverter (can't remember what all is included with the MidNite pre-wired system - it's fairly complete though). Make sure the controller is 80 Amp (either the OB FM80 or the MidNite Classic 150.

    You probably will not need 15 * 250 Watt panels: 3750 Watt array could produce up to 120 Amps of charge current. The 800 Amp hour battery bank does not need this much and a single controller can not handle it. Ten panels should work: 2500 Watts @ 77% efficiency / 24 Volts = 80 Amps.
  • JOSI
    JOSI Registered Users Posts: 11
    Re: Bimodal system to run Deep well

    Thanks Cariboocoot. THis is all starting to make a little more sence. I am still going to take a course tho.
  • mtdoc
    mtdoc Solar Expert Posts: 600 ✭✭
    Re: Bimodal system to run Deep well

    Just a point of reference:

    My system - using an Outback 3648 runs my 240V 1hp septic pump without problems. I have an Outback autotransormer to get the 240 VAC from my single 120 VAC inverter ( I assume you will be needing one as well). The pump usually only runs for about 15 seconds at a time. I had been worried that the GVFX3648 would not cut it since when I used my Fluke clamp meter to catch a measurement of the inrush current on the pump it showed over 30 amps at 240V! - but no problems. The current draw when running (after starting) is only about 6-7 amps at 240V.