Need help planning and selecting pump for Off Grid home!

Rngr275Rngr275 Solar Expert Posts: 120 ✭✭
Howdy all been a number of years since I have posted here and I'm back because I need some expert advice. Backstory; 8 years ago I joined the forum because we were buying an Amish farm and NY Electric and Gas wanted a fortune plus 2 of my children to run electric to the house. With expert input from this forum we have been happily living off grid in our new home. Details of our system (which will be needed for this discussion)  4kW solar panels, feeding 2 Midnight Classic 150 charge controllers, charging 16 Trojan RE batteries wired in series and parallel to get 740AH @ 48V, which feed the house via a Outback VFX3648 invertor. Backup generator is a Generac 6kW
Ecogen. Over all system has been great other than the batteries are starting to show there age (8years+) and usage creep as our usage has expanded (separate discussion). Here ids the current issue. Our water supply comes from a spring fed cistern in the basement or a shallow dug well. Jet pump pulls from either water source (manually set) to a large pressure tank) Pretty simple as long as you have water.

   Very dry end of summer and fall has lead to the spring/cistern drying up and the dug well barely holding on. So tomorrow morning they will begin drilling our new well. It is ~ 50-70 feet from the house and (fingers crossed) will only be 100-150ft deep, which is typical for this area according to the driller and the neighbors. I won't have the well details until the drilling is complete but I'm trying to weight all the options for getting the system up and running. My concern obviously is surge current since I am using the VFX3648 (3600W invertor) batteries are still in fairly good shape but will probably swap out next summer. I've read numerous posts here and other forums about Grundfos SQ, SQE and SQFlex pumps, Standard pumps with VFD's , 2 vs 3 wire pumps till my head is spinning. $$ always a concern but having a dependable functioning system if of utmost importance to me. We are planning to move in a few years so this will also be a selling point for the new buyers.

So without well specific details and a rough idea of what I have to work with for power what are your suggestions? And any specific details or reasoning for your suggestions would be greatly appreciated.

Thanks in Advance.... McD

Comments

  • Dave AngeliniDave Angelini Solar Expert Posts: 5,953 ✭✭✭✭✭
    Get some details. A mistake that is sometimes made is not letting the well guy install the pump and then thoroughly test it.
    Your issue with selling the place makes it hard as most offgrid property really is for a buyer that really has to love the place. Hard to justify more expense that may never come back. Maybe the C19 peak right now won't be there in 2 years. No crystal ball but good luck.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • mike95490mike95490 Solar Expert Posts: 9,298 ✭✭✭✭✭
    How much water will you require from the well ?   Will 30 gph work for you into your cistern ?   Or do you need 6GPM for irrigation ?

    How small of a pump can you get by with ?  That's the question.   Get the book for the pumps your well vendor carries, look thru the pump curves to get one for your depth and DPM that you need.   They make hundreds of pumps, but your well driller likely only orders 6 types a year, one size fits every one else.
    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 ,

  • Rngr275Rngr275 Solar Expert Posts: 120 ✭✭
    While I understand the sizing of the pump to my water needs, there are lots of pumps that will fit the bill for water usage. My issue the power limitation from my inverter and the surge draw to get the pump up to speed. I've been reading a ton and many pumps out there pull hard to get going. I was looking more for thoughts and experiences with VFD's W/ "Standard" pumps or spending the $$$ on say a Grundfos SQ, SQE or SQFlex pump. The cistern is not necessarily in play because I don't intend on filling it from the new well and even if I did I need a pump that can start and run off my 3600W inverter. BTW, the well came in at 150 feet and the static water depth is ~30ft. Thanks for replying! 
  • BB.BB. Super Moderators, Administrators Posts: 31,783 admin
    The SQE pumps are (more or less) just 3 phase pumps with an integrated VFD (and I think permanent magnet motors, at least for the SQE versions--Higher electrical efficiency vs induction motors). That gives you the soft start (very little, if any, surge current)... There are different models of Grundfos pumps. From those that only take AC power, to the SQE family that takes AC/Solar Panels/Battery power directly. (note: running from a 48 volt battery bank to an SQE pump motor generally results in lower motor Wattage/Power--Higher DC voltage input is usually required to run at full power).

    https://product-selection.grundfos.com/ae/products/sqe?tab=documentation

    The Grundfos pumps have a great reputation, seem to last 7+ years in normal operation. But are not cheap (just from what I have read, I am on city water at my home).

    The pumps that can use VFDs are a bit limited in selection... First, "native" VFD pump motors should be 3 phase, or possibly single phase with remote capacitor connection (three wire motors)--Which allows a VFD (designed for application) to run as a VFD powered motor (VFD needs access to the start winding).

    VFD (variable frequency drives) are basically variable frequency (and voltage) 3 phase AC inverters... And typically (from what I have read) output MSW (modified square wave at high(er) frequencies and "chopped" for variable power output) voltage. MSW is "hard" on induction motors (more heat, voltage spikes, vibration)--So they tend to run hotter on VFDs. There are VFD rated motors that should have a longer life than a non-VFD rated motor.

    https://cdn.automationdirect.com/static/specs/motorsselection.pdf

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,298 ✭✭✭✭✭
    And you have to weigh the cost of the expensive inverter to start the cheap pump (which can be replaced in a day if it dies)
    vs
    the cost of a fancy expensive pump and no inverter, with a week lead time to get a replacement if it fails.
    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 ,

  • Rngr275Rngr275 Solar Expert Posts: 120 ✭✭
    Thank you all .... Decided on the Grundfos 10SQ05-160-115V, 10GPM pump. From everything I've read this should fit the bill! Not cheap but hopefully I'll just buy one and done!


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