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Well pump sizing for existing system

Discussion in 'New Member Introductions' started by phoenix, Aug 6, 2017.

  1. phoenix

    phoenix Monkey

    Hello there,
    I just had a question regarding the sizing of a new pump. I have an existing home with a deep well. My tenants (whose water usage is higher than my own) are constantly running out of water. I feel it is time to replace the pump and I was looking at buying a grundfos 1 Hp soft start pump. My system is solar are fairly small (24 V system with 1100W of panels) and I run a Xantrex 2424 inverter. The research I have done it seems it would be ok to use this pump with my system but I was needing a more expert opinion before I went ahead with the purchase. Any help would be appreciated! Many thanks in advance!!
  2. Merkun

    Merkun furious dreamer

    Before you replace the pump, it behooves you/us to know a bit more. How many people are on the system? Do they take long showers? What is the horsepower of the existing pump? How old is it? How deep is the well? And a host of more electrically oriented questions before anyone here would presume to advise you.

    It is possible that the existing pump will do the job if you get a larger pressure tank rather than replacing the pump.
    chelloveck and Dunerunner like this.
  3. techsar

    techsar Monkey+++

    Another possibility is the well recovery is not up to the task...no pump is going to correct that by itself.
  4. duane

    duane Monkey+++

    In my limited experience with wells, the depth of the well, the height of the water column in the well and the size of the well bore, the time it takes water to flow back into the well and the and the amount of water that will be available to be pumped out at any particular depth are more important than the pump. If you have a 600 ft deep well as does my neighbor and it has an inflow rate of 2 gal a minute, you have to put your pump on a timer and harvest the water into a storage tank over the entire 24 hour period and draw your water out of that tank at a higher flow rate as needed. It may be that as you pump the water out, the water level in the well drops and the flow rate from the pump decreases, in that case a pump with a higher delivery rate at a greater depth may help. In most cases if a well and a pump are adequate at one rate of demand and not at another demand rate, the capacity of the well and not the pump are the problem. Yet another problem in much of the country, the static water level in the aquifer is dropping due to over pumping for industrial, agricultural or domestic use and it may be necessary to redrill your well and lower your pump level to have adequate water during the whole year.
    chelloveck likes this.
  5. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    First thing, Does this pump run continuously, or does it cycle to fill an Above Ground Tank? If it runs continuously, then what you have for Solar, ain't going to make it especially if they use much water after dark.... If you fill an Above Ground Tank, does the Tank hold enough to keep everyone supplied during the Dark Hours? If not, again, your solar is not near big enough... The last thing is. What is your Inverters Battery Bank AMPHour Capability?
    chelloveck likes this.
  6. oil pan 4

    oil pan 4 Monkey+++

    Yeah we kind of need to know all that.
    Well depth, how much water is used per day. Does it fill an above ground tank or go straight into a pressure tank?
    You say it's a deep well, that means different things in different places, like on the east coast a deep well can be well under 200', but in the rocky mountains 200' won't even hit water, their idea of deep is like 1,100'.
    Then every thing you can on the solar. How big are the batteries and how much power the panels can actualy make where you are. For example panels in new Mexico or Arizona are going to make a lot more power than if the same panels were set up in Maine. Chances are it isn't going to be nearly big enough.
    Last edited: Aug 6, 2017
    chelloveck likes this.
  7. phoenix

    phoenix Monkey

    There are 5 people on the system, 2 adults and 3 young children, very frugal in there water uses as I am aware. The pump is 25 years old and 1/2 hp. The well is 450ft deep and was fracked approx. 11 years ago.

    Yes that had crossed my mind.. we had a really wet spring and solid snow pack from previous winter but its been a dry summer, this has not been a problem while I was living there but that may have changed?!

    No it doesn't run continuously, I have a water tank in the utility room and like I said in an earlier reply it didn't ever fail when I lived there with my ex and teenage stepson! Amp hour of battery bank is approx. 270 AH.
    Last edited by a moderator: Aug 6, 2017
    chelloveck likes this.
  8. phoenix

    phoenix Monkey

    The well depth is 450' although not sure what depth the pump is set to.. it goes straight to a pressure tank. Solar I have addressed in my question, batteries are set up in series/parallel. Yes living in VT we don't get the same sun as in Arizona and its hard to say since it varies from day to day. We don't get many full sun days, a lot of overcast days...as I mentioned in a previous reply it hadn't been a problem for 11 years when I lived there with 2 adults and a teenage stepson.
    chelloveck likes this.
  9. Dunerunner

    Dunerunner Brewery Monkey Moderator

    Is that the AH of the entire battery bank, or just one battery?

    and, welcome to the Monkey
    chelloveck likes this.
  10. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    Sounds like T-105 GolfCart Batteries in series for 24Vdc Bank Voltage...
    chelloveck and Dunerunner like this.
  11. Dunerunner

    Dunerunner Brewery Monkey Moderator

    Where is the face palm emoticon... I assumed 24V batteries in parallel. DUH!!
    chelloveck likes this.
  12. phoenix

    phoenix Monkey

    Sorry, yes one battery....and I have 12 of them.

    Yep you got it, new interstate batteries in 2013.
    Last edited by a moderator: Aug 7, 2017
    Dunerunner likes this.
  13. Dunerunner

    Dunerunner Brewery Monkey Moderator

    So, four in series to yield the 24V, 3 banks of four batteries in series then connected in parallel? 810AH

    Or three independent banks of four batteries in series that you switch between? 270AH
    Last edited: Aug 7, 2017
  14. phoenix

    phoenix Monkey

    Yes correct the first time... 810 AH sounds about correct ... and thanks for the welcome always fascinating stuff to learn!
    Dunerunner likes this.
  15. ghrit

    ghrit Bad company Administrator Founding Member

    Please remember that lead acid batteries are not always fond of being discharged too far. To say that your 800 or so amphours may not all be usable.
    Dunerunner likes this.
  16. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    So what you really have is about 400 AmpHours @ 24Vdc of useable, repeatable, Energy... You should NEVER except in a very RARE Emergency, discharge Lead Acid Batteries below 50% of capacity.... If you go below that, a few to many times, your batteries will be fried.... and need to be replaced.
    I run 1200 AmpHours of L16HDs @ 24Vdc and they rarely ever go below 75% charge, (determined by Specific Gravity) and I usually get around 8-10 years of service out of a Battery Bank.... I am getting a New Bank this Year... ($3000US plus Freight)
    Dunerunner likes this.
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