AC or DC

97TJ97TJ Solar Expert Posts: 57 ✭✭
My plan is to pump water from an underground cistern to a 55 gal tank inside my cabin. From there another pump will send water to sinks/shower from there. I'm thing a couple of pumps along the lines of the shurflo on demand type pumps. Does it really matter if I go AC or DC. They make both.

Comments

  • vtmapsvtmaps Solar Expert Posts: 3,739 ✭✭✭✭
    Re: AC or DC

    Are you on or off grid? That is one consideration. If you are off grid and already have DC, I think the DC pumps are slightly more efficient. Also, a DC system may be more reliable (if your inverter fails you still have water). There are a number of good reasons to use AC. If your cistern is far away, AC requires smaller gauge wires. The pump in the house will turn on and off based on its pressure switch. How will the cistern pump know when to turn on and off? Its easier to switch AC than DC.
    -- vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: AC or DC

    Why not avoid th middle man, install a shurflos submersible, and pump directly into the p tank? You can pump water only when the sun shines to reduce the load on the battery if you have enough tank capacity.

    Tony
  • 97TJ97TJ Solar Expert Posts: 57 ✭✭
    Re: AC or DC

    The cabin is completely off grid. Water source is primarily catch water although I may sink a shallow well this summer.
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: AC or DC

    How high do you have to lift water (suction head)? Small Shureflos will push water into ~ 50 psi (or more depending on model) but they will only "pull" water a few feet. I just got tripped on an installation. We had to draw less than 5 vertical feet, and it worked fine in beta testing, pumping into 50psi tank. Moving the suction line to the far side of the house, then along the ground into the lake, a total of ~75' (still the same 5' lift) the pump would not prime. even when primed by hand it still wouldn't pump.

    So I go back to my suggestion,, consider a submersible Shurflo 9300, it will pump into 50 psi at a very acceptable rate ~3 gpm.

    Tony
  • 97TJ97TJ Solar Expert Posts: 57 ✭✭
    Re: AC or DC

    Well the layout is like this. The cistern is a 550 gal plastic located in an underground root cellar about 20' from the cabin. My plan is to put a pump inline next to the cistern and push the water to a 55 gallon tank inside the cabin. From there use a second pump to push water to shower and sinks from the 55 gallon tank. I don't know if I could get away with one pump, but my though was to divert catch water directly to the tank inside the cabin when the cistern is full and save that for a non rainy day.
  • SCharlesSCharles Solar Expert Posts: 123 ✭✭
    Re: AC or DC
    97TJ wrote: »
    Well the layout is like this. The cistern is a 550 gal plastic located in an underground root cellar about 20' from the cabin. My plan is to put a pump inline next to the cistern and push the water to a 55 gallon tank inside the cabin. From there use a second pump to push water to shower and sinks from the 55 gallon tank. I don't know if I could get away with one pump, but my though was to divert catch water directly to the tank inside the cabin when the cistern is full and save that for a non rainy day.


    You will be money and pump longevity and hassle ahead if you add into this setup a pressure tank, with pressure switch to trigger the indoor pump. Your pump, then, might only come on a couple times a day, if you are showering. The switch will be maybe $14, don't know about the pressure tank but I paid less than a hundred bucks for a 40 gallon one back in the 90s at Sears. Perhaps you are already planning one.
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: AC or DC

    The shurflo pumps have built in pressure switches. I would pump directly into a p-tank, even two if you wish to pump only when the sun is out. For example, my 50 gallon tank will deliver ~15 gallons of water before the pump cycles. If you used to tanks, you could draw ~ 30 gals between pump cycles.. I see no need for two pumps.

    Bottom line,, KISS!

    Tony
  • vtmapsvtmaps Solar Expert Posts: 3,739 ✭✭✭✭
    Re: AC or DC
    97TJ wrote: »
    My plan is to put a pump inline next to the cistern and push the water to a 55 gallon tank inside the cabin. From there use a second pump to push water to shower and sinks from the 55 gallon tank. I don't know if I could get away with one pump,
    You can (and should, IMO) use just one pump (at the cistern). As SCharles points out you do need a pressure tank.
    You might also consider one of the Shurflo Extreme pumps, which do not require a pressure tank:
    http://www.solar-electric.com/shexsepu.html
    The extreme pumps are DC only. Shurflo makes the the Extreme pump in two capacities. Our host only has the larger one in their catalog. You can find the smaller one at Shurflo's website.
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • 97TJ97TJ Solar Expert Posts: 57 ✭✭
    Re: AC or DC

    OK, thank you for the suggestions.
  • monolocomonoloco Solar Expert Posts: 103 ✭✭
    Re: AC or DC
    vtmaps wrote: »
    You can (and should, IMO) use just one pump (at the cistern). As SCharles points out you do need a pressure tank.
    You might also consider one of the Shurflo Extreme pumps, which do not require a pressure tank:
    http://www.solar-electric.com/shexsepu.html
    The extreme pumps are DC only. Shurflo makes the the Extreme pump in two capacities. Our host only has the larger one in their catalog. You can find the smaller one at Shurflo's website.
    --vtMaps
    I have the Jabsco version of this pump, the variable speed works great but the pump shuts down when my batteries reach max charge.
  • Oscar13601Oscar13601 Registered Users Posts: 18
    Re: AC or DC

    I have a similar problem like 97TJ. I have a 190' deep water well. I want to install a submergeble pump that would not give me any problems in the future. I'm thinking on a 40-60 galon press tank. Do you guys think the DC 3 gal/min will do the job, or should I go with the 120V AC connected to the inverter. I saw a post on one of the forums that said the the 120V AC needs an inverter of 1200-1750Watts. Is this for the spike in power when the pump starts?? I'm very new at this and need some advise. The way i think the setup would be is: submergible pump, pressure tank, faucets... Is that the way it normally is???, or em' I forgetting something???? Thanks guys....
  • BB.BB. Super Moderators, Administrators Posts: 32,015 admin
    Re: AC or DC

    Are you 100% off grid, or are you looking for emergency backup... Also, what is your overall power use per day (Watt*Hours/kWH, peak watts, etc.)?

    You have two basic ways to go... One is a pump+pressure tank (as you suggest) and another is to use the well pump to fill a cistern, and then use a smaller AC or DC pump to pressurize your home water system.

    If you can use a cistern (also very handy for fire suppression, required by some localities), you can "slow pump" into the cistern (smaller well pump) and use a small pump or two for local water pressure. The well pump could then be powered by a pure solar array (no batteries, less costs, less maintenance), and the surface pump would only need a small battery bank for 24 hour water.

    If you already have a large off grid power system--Then choosing the in-well pump type is more of an issue of how long of power run from the battery bank/inverter to the well. Higher voltage means less wiring drop/smaller copper cables.

    There are some neat newer AC pump controllers--Variable Frequency Drives--Which use three wire single phase (remote/well head starting capacitor) or 3 phase pump motors. Can decrease starting current and be more efficient (variable pump RPM to match water flow requirements).

    There are a lot of option out there--Knowing more about your needs would be helpful.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,362 ✭✭✭✭✭
    Re: AC or DC
    Oscar13601 wrote: »
    I have a similar problem like 97TJ. I have a 190' deep water well. I want to install a submergeble pump that would not give me any problems in the future. I'm thinking on a 40-60 galon press tank. Do you guys think the DC 3 gal/min will do the job, or should I go with the 120V AC connected to the inverter. I saw a post on one of the forums that said the the 120V AC needs an inverter of 1200-1750Watts. Is this for the spike in power when the pump starts?? I'm very new at this and need some advise. The way i think the setup would be is: submergible pump, pressure tank, faucets... Is that the way it normally is???, or em' I forgetting something???? Thanks guys....

    Water pumping. If you only need a small amount, you can go with solar and DC. If you are running a house, and need water to flush a toilet in the middle of the night, you still don't need a lot, just enough in a pressure tank to flush, and a slow re-pressurizion of the tank. Also factor in shower usage (flow for several minutes - can the pump keep up with that?) garden hose for outside, and other appliances needing water. your choices:
    • Pump from deep, to an above ground 1,000 gal tank, and then use a 2nd pressure building pump & 50gal pressure tank
    • Pump from deep to an elevated tank, and let gravity do the work ( I do this with 12,000 gallons of tanks, one ON cycle per day )
    • Pump from deep & 50gal pressure tank (this causes many on-off cycles of the deep pump)


    So it depends on your infrastructure (elevated tank, above ground tank, or pressure tank only) as to your choices.

    If I was to put a pump 190' down a well, I'd look for a generic 240VAC pump, that have hundreds of thousands installed world wide, and every pump and well dealer has spares. they last 10-30 years, and cost a couple hundred $ to completly replace.

    DC pumps are expensive, parts may not be nearby, and few know about repair and maintainance.

    It takes a fair sized battery bank and inverter to power the starting surge for a AC pump, but if you are off grid, you may need that gear anyway. So add up the prices and pros / cons for each system your site can handle, and see where it gets you.
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  • Oscar13601Oscar13601 Registered Users Posts: 18
    Re: AC or DC

    I was thinking on the 120V AC Pump (well pump) and a 50gal pressure tank. This may cause many on-off cycles of the deep pump, but if I install an independant switch for the pump. Turn it on once or twice a day, denpending on the need of the house. Would this work??
    I mean, preventing the on-off from pump to prevent drainage from battery bank. Just turn on when need it.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: AC or DC

    Did I read 190' deep well? If so, that is going to be a 240 VAC pump. Probably 1 HP.

    My system works much the way you describe: it can not turn on unless I let it do so, and I only let it when the batteries are fully charged or if the gen is running. When it is on it fills a 60 gallon pressure tank which supplies enough water for two of us for a day. We time other major water use (like laundry) for when the pump is on. Even so, I'm thinking of adding a second tank.

    I'm also thinking of increasing the power system capacity because the kids use much more water than we when they're there and don't seem to be able to comprehend "run the gen if you need water at night".
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