Small cabin DC water pump set-up?

HairfarmHairfarm Posts: 208Solar Expert
Greetings,

I've read this link, but still had some questions:
http://www.windsun.com/Solar_Water_Pumps/pumpinfo1.htm

Details:
Small off-grid cabin.
2800 gal. water storage container (above ground and 3 feet away from the cabin)
80 gallon (30 gallon water capacity with bladder) pre-pressurized tank

As it stands I'm using an AC flotec pump (1/2hp - 115v - 9.4A). I'm still in the construction phase (and don't have solar installed yet) so I power the AC pump with a 5k generator. This is plenty for the pump with a surge of 3300.

Eventually, I plan to use a DC pump with my system. The DC pump only has to pull water from 4 feet away into a pressure tank that is two feet away. The water is already stored above ground which should be easier on the DC pump because it doesn't have to draw from a well. I would like to have water pressure of 45-50 lbs.

Based on my specs, I was hoping for a recommendation on a DC pump with a built-in pressure switch that will fill my pressure tank to 45-50lbs and run off of a 12v battery bank (recharged by 1000k of PV). Hopefully something moderately priced. Sureflo?

Lastly, I would still like to keep the AC pump in line for emergencies. Can I have two pumps in line? Anyone else have a set up like this, with two pump types (AC & DC) in the same line?

thanks,

Hairfarm

Comments

  • BB.BB. Posts: 24,526Super Moderators admin
    Re: Small cabin DC water pump set-up?

    Should not be a problem... You probably would want to plumb in a pair of ball valves per pump (or similar) to isolate each pump from the common water pipes (or at least check valves to prevent back flow through one or the other pumps)... That way you can still have pressurized water while the other pump is being serviced.

    If you have freezing conditions, adding a drain valve will be a help too.

    Regarding what kind of pump... There are simple DC pumps that will last a couple years between overhauls (new diaphragms and motor brushes)... If you will be pumping a fair amount of water, a brushless (PM type) motor with electronic control would be nice for a longer service life.

    Also understanding how much sand/grit you have in your water will be a help... Grit in the wrong type of pump will quickly kill them. Using filters on the water inlet can create its own problems (pump pulls a vacuum on the inlet and stops pumping).

    There is quite a range in pricing between a "simple" and a "nice" pump:

    Shurflo 8000 standard delivery pump 12 volt ($100)
    Shurflo Extreme smart sensor 5.7 RV pump 12 Volt ($340)

    Others here who have more experience with off-grid pumping can probably give you more information than I.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • HairfarmHairfarm Posts: 208Solar Expert
    Re: Small cabin DC water pump set-up?

    Thanks for the helpful response BB.

    As it is, when the 30psi cut-in switch kicks in it will take roughly 2 minutes (give or take) for my AC pump to fill my pressure tank (80 gal capacity - 30 gal water). My pressure switch settings are 30-50.

    Question: How long will it take a DC pump to fill my pressure tank? Will it be much slower than my AC pump?

    thanks!

    Hairfarm
  • BB.BB. Posts: 24,526Super Moderators admin
    Re: Small cabin DC water pump set-up?

    Your AC pump is around 1,000 watts... The 12 VDC pumps I linked to are around 4.5-9.5 amps -- or ~114 watts maximum. So, at the very least, I would expect them to run 10x as long for otherwise identical / same efficiency pumps (the small DC pumps may actually turn out to be more efficient).

    You should find a data sheet for the pump you are interested in... For a random 12 volt pump, here is one PDF data sheet.

    At 30 PSI it runs about 2.3 GPM at 8.4 amps. At 50 PSI it is 1.8 GPM at 9.5 amps.

    So, around 2 GPM for 30-50 PSI.

    30 gallons will take around 15 minutes to fill (if I understand your setup).

    -Bill "I think" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • train82499train82499 Posts: 11Registered Users
    Re: Small cabin DC water pump set-up?

    I use a Shurflo and no pressure tank for small cabin. It has pressure switch built in. Powers shower, sink and etc. They are only 2 or 3 gallons per minute - so problems with running several taps open. Our host has a cool looking one at http://store.solar-electric.com/2088-514-145.html but the less expensive models likely as good. And even cooler one at http://store.solar-electric.com/sh41potw12vo.html . I use http://store.solar-electric.com/2088-443-144.html and its fine.

    I see they have both 12v and 24v units.

    Locate below the suppy as they do not pull too well and are meant to push.

    Get a filter mounted before the unit if there is chance of junk in the line - save the pump.

    There are many places that sell these and parts are available everywhere.

    Not tried one with a pressure tank - they pump at 45 psi. Would be interested in experience of those with Shurflow and a pressure tank also - sounds complicated.

    The company product line (go for the RV units - this is the market they corner) is at http://www.shurflo.com/rv-products/rv-pumps/default.html .

    See also
  • PhilSPhilS Posts: 369Solar Expert ✭✭✭
    Re: Small cabin DC water pump set-up?

    I have a cistern that normally supplies an AC pump to fill two pressure tanks. I also have a 12VDC Shurflo pump as a backup to that AC pump, using (as suggested) ball valves to isolate the two.

    If the AC pump fails then two valves are shut for it, two are opened for the DC pump, and a fuse is relocated to supply the DC pump power and a breaker is switched so the AC pump doesn't get power. Less than a minute total.

    Yes, it takes longer for the DC pump to get the tanks up to pressure, but it's no big deal. On those few times we've been on the backup, we never got to a point where the DC pump couldn't keep up with demand (like a shower or washer) and still fill the pressure tanks.

    Phil
  • bmetbmet Posts: 630Solar Expert
    Re: Small cabin DC water pump set-up?

    Could you rate your shurflo pumps? Have they been durable for your usage?
  • HairfarmHairfarm Posts: 208Solar Expert
    Re: Small cabin DC water pump set-up?

    train82499 -
    I use a Shurflo and no pressure tank for small cabin.

    How do you get stable water pressure? What's the shower experience like with no pressure tank? Do you get hammering in your lines?


    PhilS - What type of DC pump do you use? How many gallons is your PT?


    BB - Are all Sureflo DC pumps positive displacement? I like the ball valve set up and idea of having an AC backup running off of my generator.

    thanks!

    Hairfarm
  • BB.BB. Posts: 24,526Super Moderators admin
    Re: Small cabin DC water pump set-up?

    I believe that the ones I pointed at are all positive displacement pumps.

    But they also make some other types too (like a sump pump)--and other models that NAWS does not carry.

    I have no directly knowledge of the product line--You should contact NAWS, Shurflo, or your local supplier for details.

    Otherwise, I am just searching the web for information too.

    I have a small DC pump in an old RV (may even be a very old Shurflo)--And no pressure tank... Pump simply turns on when a faucet is opened. Probably not ideal for a cabin/home where a pressure tank would be a lot nicer (and handle multiple points of use at the same time).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Posts: 5,070Super Moderators admin
    Re: Small cabin DC water pump set-up?

    We use small shuflos without tanks in small seasonal cabins. They work fine for one appliance at a time. Given a choice, I would instal at least a small P-tank to reduce cycling.

    Tony
  • train82499train82499 Posts: 11Registered Users
    Re: Small cabin DC water pump set-up?

    Shurflo works great to run one outlet at a time. EG it does excellent job in a shower, or doing the dishes etc. But it can only pump out 3 GPM or so and therefore if you are drawing more than that the pressure drops. Pressure is fine - one tap at a time, eg 45 psi or so.

    I wonder how I would hook up a pressure tank to my Shurflo - just run a water line from the pump to the tank and out the other end back into the system? That might be a very good idea!

    :)
  • dwhdwh Posts: 1,332Solar Expert
    Re: Small cabin DC water pump set-up?
    train82499 wrote: »
    I wonder how I would hook up a pressure tank to my Shurflo - just run a water line from the pump to the tank and out the other end back into the system? That might be a very good idea!

    :)

    That's one way. The RV type accumulator tanks are mostly like that - they have an in and an out (doesn't matter which way you hook it up). Bigger house types usually just have a single water fitting on one end and an air valve stem on the other and you just T into the pressure line somewhere.

    http://www.shopwiki.com/accumulator+tank
  • PhilSPhilS Posts: 369Solar Expert ✭✭✭
    Re: Small cabin DC water pump set-up?
    Hairfarm wrote: »
    train82499 -


    How do you get stable water pressure? What's the shower experience like with no pressure tank? Do you get hammering in your lines?


    PhilS - What type of DC pump do you use? How many gallons is your PT?


    BB - Are all Sureflo DC pumps positive displacement? I like the ball valve set up and idea of having an AC backup running off of my generator.

    thanks!

    Hairfarm

    bmet The Shurflow pump has been just fine, but remember it is only a backup. I've used Shurflow pumps in my RVs and never had a problem.

    hairfarm 12V Shurflow, made for an RV

    I have two pressure tanks. Both are about 5' tall. I'd guess 30 gallon capacity since they appear to be about 50 gallons each and almost half of a bladder tank doesn't have water. But I'm only guessing. They are plumbed in parallel.

    I also have a third pressure tank mounted at the wellhead. Since my cistern is 75ft away, I had a water hammer problem when starting and stopping the well. The pressure tank at the well stopped that. It also gives me another complete water supply for the house if I was to have problems with the main system... change a few valves and the main system is disconnected, the secondary system is online.

    Whether it's water or power, I have backup systems in place, and backups for the backup systems. That's a carryover from the years I spent on a submarine... we had at least three levels of redundancy for any critical system.

    Phil
  • HairfarmHairfarm Posts: 208Solar Expert
    Re: Small cabin DC water pump set-up?
    I have two pressure tanks. Both are about 5' tall. I'd guess 30 gallon capacity since they appear to be about 50 gallons each and almost half of a bladder tank doesn't have water. But I'm only guessing. They are plumbed in parallel.

    PhilS -

    So between your two PT's, it sounds like you have roughly 60 gals of water capacity.

    1. How many minutes does it take to fill both of them with your single surflo dc pump?

    2. And you said that the sureflo DC pump was a backup system so what is powering your AC pump if you're off-grid? A propane generator or battery backup from PV?

    Your set up sounds very useful.

    thanks,
  • PhilSPhilS Posts: 369Solar Expert ✭✭✭
    Re: Small cabin DC water pump set-up?
    Hairfarm wrote: »
    PhilS -

    So between your two PT's, it sounds like you have roughly 60 gals of water capacity.

    1. How many minutes does it take to fill both of them with your single Shurflo dc pump?

    2. And you said that the Shurflo DC pump was a backup system so what is powering your AC pump if you're off-grid? A propane generator or battery backup from PV?

    Your set up sounds very useful.

    thanks,

    I've never timed how long to fill the tanks, on the DC pump or the AC pump. We've never had the pressure fall to the point where the only flow was from the pump (either of them). It's been a non-issue and worked flawlessly. The last time the DC pump was used was when we were out of town and the housesitter "ran out of water". The pressure switch on the AC pump had failed. Simple instructions on the phone got water pressure back.

    Most failures happen when we are gone, but it's usually not the fault of our "housesitter" but, of course, they assume it's something they've done wrong. That pressure switch was less than 6 months old and came with a new pump. The new pump was installed after another time we were out of town and the pump motor failed (it was running off of an older Heart Interface MSW inverter). The housesitter again thought it their fault. Murphy usually rules.

    I've since made an "operators manual" for our home. It covers water and electricity and all the systems and backups.

    The AC pump is powered by our old Xantrex (Trace) SW2500MC Inverter. Unless the generator is running, in which case the Trace charges and the gen power is passed through to the pump.

    Phil
  • HairfarmHairfarm Posts: 208Solar Expert
    Re: Small cabin DC water pump set-up?
    The AC pump is powered by our old Xantrex (Trace) SW2500MC Inverter. Unless the generator is running, in which case the Trace charges and the gen power is passed through to the pump.


    Question:

    It sounds like your primary pump is an AC pump and your backup is a DC pump. Is this correct? Why not use the DC pump as your primary since it is more efficient use of battery power? It was my understanding (and I'm still very new at this) that an AC pump would make for a better back up pump...unless you have gobs of battery power to invert for a stronger AC pump. Hope that makes sense.


    Lastly, I too would like to have an inverter set up that would allow me to charge my batteries at the same time as I power other AC devices online using a generator.

    So basically there is an inverter that will allow AC generator power to pass through it to charge batteries? What type of inverter is it and who makes the better ones?

    Thanks,
  • PhilSPhilS Posts: 369Solar Expert ✭✭✭
    Re: Small cabin DC water pump set-up?
    Hairfarm wrote: »
    So basically there is an inverter that will allow AC generator power to pass through it to charge batteries? What type of inverter is it and who makes the better ones?

    Thanks,

    Both of my Magnum inverters (MS2812) will do this (although only one is designated to charge batteries). My Xantrex SW2512 will do this also. I was under the impression that most large inverters will charge batteries when the generator is running and pass the gen power on to the loads if wired that way (my second Magnum doesn't have the generator wired to the "line in" so that it provides only pure power for entertainment).

    The AC water pump is designated the "main" pump because it pumps faster. Since it's only a matter of 4 valves and two power sources, it'd be easy to swap the "main" and "backup" designations. Also, using the 12VDC pump as backup also means some more redundancy... for whatever that's worth. If it was necessary, I could run jumper cables from a vehicle to provide water pressure.

    I'd also guess that for normal duty the AC pump would last longer?

    Phil
  • SCharlesSCharles Posts: 122Solar Expert ✭✭✭✭
    Re: Small cabin DC water pump set-up?

    The only inverter I have experience with is the Trace 2512 we've had for a couple decades. When I bought it, the battery charging feature was an option, and I've seen that for other brands/models, too. Don't know if they are coming with a charger as standard these days.

    There are different reasons for choosing an a/c or d/c pump. In our case, we have a Granfos well pump which is A/C because it is 300 ft. from our battery bank. Which is in the house. Running wiring for D/C that far was out of the question. A/C [120] was no problem. I only run that pump during sunny spells to fill a cistern. From the cistern, I use a D/C Dankoff pressure pump and a pressure tank to run the household water. The Dankoff is very effective and very efficient and runs directly off the battery bank with no inverter needed.

    I could have bought a D/C well pump, but I'd have needed a separate charging system/battery bank [photovoltaics] down there at the pump for several thousand bucks. I opted to run the A/C wiring down there instead and use my house inverter/battery bank instead.

    I was told early on by a pump installation co. that I would need a certain pump which turned out to have a 60+ amp start surge. I did my own research and found this Granfos with soft start which draws, I think it is, 11 amps. 60 amps is way too much for the Trace 2512, which, if memory serves, maxes out at around 45 amps. The soft start model cost me about a hundred bucks more than the "standard" pump.
  • PhilSPhilS Posts: 369Solar Expert ✭✭✭
    Re: Small cabin DC water pump set-up?
    SCharles wrote: »
    The only inverter I have experience with is the Trace 2512 we've had for a couple decades. When I bought it, the battery charging feature was an option, and I've seen that for other brands/models, too. Don't know if they are coming with a charger as standard these days.

    There are different reasons for choosing an a/c or d/c pump. In our case, we have a Grundfos well pump which is A/C because it is 300 ft. from our battery bank. Which is in the house. Running wiring for D/C that far was out of the question. A/C [120] was no problem. I only run that pump during sunny spells to fill a cistern. From the cistern, I use a D/C Dankoff pressure pump and a pressure tank to run the household water. The Dankoff is very effective and very efficient and runs directly off the battery bank with no inverter needed.

    I could have bought a D/C well pump, but I'd have needed a separate charging system/battery bank [photovoltaics] down there at the pump for several thousand bucks. I opted to run the A/C wiring down there instead and use my house inverter/battery bank instead.

    I was told early on by a pump installation co. that I would need a certain pump which turned out to have a 60+ amp start surge. I did my own research and found this Granfos with soft start which draws, I think it is, 11 amps. 60 amps is way too much for the Trace 2512, which, if memory serves, maxes out at around 45 amps. The soft start model cost me about a hundred bucks more than the "standard" pump.

    I can second your observation that the Grundfos well pump operates flawlessly off of an SW2512 inverter (our pump is 340 deep, comparable to your 300' from the house). In my case, even if the jet pump for the house pressure (1/2hp IIRC) comes on at the same time I'm pumping the well into the cistern, there is no noticible problem. These two pumps are powered from this inverter. Plus the occasional power tool and/or shopvac, tho I can't remember ever using other tools when I was pumping.

    I guess our inverters are almost the same. Mine is marked Trace and has a sticker for Xantrex added. My inverter is SW2512MC, which is the SW series (56 step waveform, 2500w, 12V, Motor Coach configuration which gives some other menu options, like "quiet time"). I've had it a long time, I guess not as long as you've had yours... tho maybe, the MC configuration meant it came with the charge capability inititally because I don't remember ordering "charge" as an option.

    Phil
  • HairfarmHairfarm Posts: 208Solar Expert
    Re: Small cabin DC water pump set-up?
    - SCharles -
    The only inverter I have experience with is the Trace 2512 we've had for a couple decades. When I bought it, the battery charging feature was an option, and I've seen that for other brands/models, too. Don't know if they are coming with a charger as standard these days.

    There are different reasons for choosing an a/c or d/c pump. In our case, we have a Granfos well pump which is A/C because it is 300 ft. from our battery bank. Which is in the house. Running wiring for D/C that far was out of the question. A/C [120] was no problem. I only run that pump during sunny spells to fill a cistern. From the cistern, I use a D/C Dankoff pressure pump and a pressure tank to run the household water. The Dankoff is very effective and very efficient and runs directly off the battery bank with no inverter needed.

    I could have bought a D/C well pump, but I'd have needed a separate charging system/battery bank [photovoltaics] down there at the pump for several thousand bucks. I opted to run the A/C wiring down there instead and use my house inverter/battery bank instead.

    I was told early on by a pump installation co. that I would need a certain pump which turned out to have a 60+ amp start surge. I did my own research and found this Granfos with soft start which draws, I think it is, 11 amps. 60 amps is way too much for the Trace 2512, which, if memory serves, maxes out at around 45 amps. The soft start model cost me about a hundred bucks more than the "standard" pump.


    Ok. I see now. I was under the impression that it was a no-no to power an AC pump off of batteries. Inefficient. But it sounds like you're doing that to draw water from 300ft away - but, I assume, only on sunny days to not tax your batteries. This is a great idea. When (and if) I get a well (trucked in water now) I will keep this system in mind.
    - PhilS - I can second your observation that the Grundfos well pump operates flawlessly off of an SW2512 inverter (our pump is 340 deep, comparable to your 300' from the house). In my case, even if the jet pump for the house pressure (1/2hp IIRC) comes on at the same time I'm pumping the well into the cistern, there is no noticible problem. These two pumps are powered from this inverter. Plus the occasional power tool and/or shopvac, tho I can't remember ever using other tools when I was pumping.

    When using a gas generator to charge the batteries through a "charger" inverter, is the charge controller involved anywhere in this process? Or is the charge controller only used to regulate the PV and/or wind coming in to the batteries?

    In other words does the gas generator do this:

    1) Gen>charge controller>charging inverter>AC power

    or does it do this:

    2) Gen>charging inverter>AC power

    I'm wondering why batteries need a charge controller for PV and wind but not for a generator. Hope that makes sense.

    Thanks for the great info! This has really set me on the right track for my cabin.

    Hairfarm
  • SCharlesSCharles Posts: 122Solar Expert ✭✭✭✭
    Re: Small cabin DC water pump set-up?
    Hairfarm wrote: »
    Ok. I see now. I was under the impression that it was a no-no to power an AC pump off of batteries. Inefficient. But it sounds like you're doing that to draw water from 300ft away - but, I assume, only on sunny days to not tax your batteries. This is a great idea. When (and if) I get a well (trucked in water now) I will keep this system in mind.





    Well, there is some loss in efficiency by running A/C from D/C batteries, of course. But the point is, you must consider all the factors to determine whether it would be better, in your particular case, to go with one system [for pumping] over another. I have a 2000 W. solar array and a 2512 inverter and a large battery bank. In my situation, it was much less expensive to buy 6 ga. wire, direct-burial, to run the 300 ft. to the well head than to purchase, install, and have to maintain a separate PV system down at the well to run a pump. Lots more money. Lots. I already had an inverter which would do the trick, with a soft-start model pump, and excess solar elec. on sunny days.

    The soft-start version of the pump I wanted [wanted due to its pumping rate, head, etc.] cost me a little more. The wiring and junction boxes cost me more. I had to dig a long trench in rocky soil, and so on. Still made sense, in our case, to do it this way.

    We also have a 2000 gal cistern up at the house. I am able to top off that cistern any time I feel like [and the sky is clear]. So, once every couple months, I add some water. One must be ok with monitoring water level, running his pump when the sun shines and making certain it is all off when the sun isn't shining. For most off-gridders, this is no big chore.

    A system such as the one I've come up with could be automated, somewhat, with a level switch in the cistern and a way to turn on the pump when there is excess PV electrical current. However, I decided that it is simply too simple to do it by hand: I look in the cistern now and then and see what the water level is. I look at the sky and see whether it is clear and check my batteries. I have the wiring to the pump on a separate circuit breaker and box up at my battery/inverter room and simply flip on the switch to start the pump. And so on.

    For us, this all works great. By the way, my Grunfos is a 5 gpm model and that also works great for us. I can add 300 gph of water to our 2000 gal. cistern every hour, so if it is half empty, I can top off in just a few hours of sunlight.

    This set-up would not work if we needed to pump water from the well at night or on cloudy days; it would require either a larger battery bank or a generator back-up at night. We draw from the cistern, when necessary, with the Dankoff booster pump [12 v.].

    A D/C pump down at the well with a dedicated PV charging array and controller and battery back-up would be more efficient, but we have excess PV power from our existing [and paid for] PV system, and this uses some of it. And I was able to keep things a bit simpler by hooking in with my existing house PV system.

    By the way, my original plan was a dedicated PV set up down at the well. However, when I got to pricing all I'd need to set it up, I came up with thousands of dollars and the wiring, etc., was less than a thousand bucks. [Three wires, multistrand 6 ga. plus breakers, etc.] My brother-in-law is a retired electrician and we worked out the losses in voltage due to the distance and amperage draw and wire gauge. Mine was only a few percent at 120 v.

    By the way, my well is 328 ft. deep in SOLID rock, so I had a well drilling co. do it. The well is about 100 Ft. lower than the house and cistern. However, ours turned out to be a "flowing" well, so the head the pump sees is only that 100 Ft. This allowed me to use a slightly less powerful pump than otherwise and to use a 120 v. pump rather than 220. [which would have required a different inverter] I mention this because I also hired a co. to set the pump. They also provided the pump. It took me a number of conversations with them to convince them I wanted a soft-start pump. [Without the soft-start feature, I'd need a different and more expensive inverter as the regular pump has a 60 a. draw to start and the soft-start has about 11 a. draw, well within my Trace's spec's.] They just could not get their heads around the idea of not running a more powerful pump with a higher flow rate. They told me time after time I'd be happier by purchasing a large generator and running it in order to pump my water. They told me at the outset that they'd worked with off-gridders a number of times and understood things from our perspective. In reality, they did not "get it" and I had to insist on no-generator pumping. Once we were done, they were pretty impressed and finally began to understand. If you do work with someone like this, you need to be firm in what you want and what your system would handle.
  • dwhdwh Posts: 1,332Solar Expert
    Re: Small cabin DC water pump set-up?
    Hairfarm wrote: »
    When using a gas generator to charge the batteries through a "charger" inverter, is the charge controller involved anywhere in this process? Or is the charge controller only used to regulate the PV and/or wind coming in to the batteries?

    In other words does the gas generator do this:

    1) Gen>charge controller>charging inverter>AC power

    or does it do this:

    2) Gen>charging inverter>AC power

    I'm wondering why batteries need a charge controller for PV and wind but not for a generator. Hope that makes sense.

    Thanks for the great info! This has really set me on the right track for my cabin.

    Hairfarm

    The solar/wind charging system is separate from whatever other charging system.

    Looks more like:

    PV->charge controller->battery<->inverter/charger<-generator
  • waynefromnscanadawaynefromnscanada Posts: 3,009Solar Expert ✭✭✭✭
    Re: Small cabin DC water pump set-up?

    Having lived most of my life with our own private water pumping systems, I can possibly shed some light and give you some food for thought. My well is about 250 feet from the house and the water level about 15 feet below the basement floor. I do have two pumps, sharing one water line. In the well is a 1/2HP 220 volt, standard every day submersible pump. At the outlet of the pump is a "T", which connects to a foot valve which has nothing to do with the submersible pump, rather it's there to supply the 1/4 HP piston pump in the basement when it runs. If for any reason I decide to use the submersible pump, it drives the water up the line, right through the piston pump (which would not be running) and into the tank. Switching off when the tank pressure reached 50 PSI. The valves in the piston unit just open and let the water pass right through. no problem. But for the last year and a half, only the piston pump has been used. It's 1/4 HP 120VAC motor is rated at 5 amps, but using a Kill-a-watt meter, I see it draws less than 300 watts, even less at lower pressures. So, considering it runs off one of my inverters, I lowered the pressure to 25 to 45 PSI. I can live with that, especially knowing I'm using less from the batteries. Also, I use one of the two contact sets in the pressure switch, as a remote switch for the inverter, so unless I'm using the inverter for something else, it only runs when the pressure switch calls for water. When the piston unit starts, the suction it creates in the water line to the well opens the foot valve, and draws water in that way, instead of trying to suck it through the submersible pump. Works awesome! Actually I guess it will be 2 years come January, since the sub pump was last started. Piston pumps are not that common any more, but they are still available and unlike 50 years ago, can now be had with Stainless Steel water boxes. I love the piston pump, it's WAY easier on the renewable energy system that the sub unit. My tank is air bladder type of course, 20 gal, don't remember the "draw down" before the pump restarts, but I think about a bucket and a half. It takes a total of very slightly over 1 AH out of the 12 volt system every time it cycles, which isn't bad at all!
    And yes, for over a year I ran it on a 1500 watt MSW inverter, knowing it would be less efficient, but since it hardly ever ran more than a minute or so at a time, the motor never got the chill off it. And for easy starts, the motor is capacitor start. A non cap start 1/4 HP 120 volt motor can be changed to Capacitor start (as this one was) very successfully by adding a 400mfd starting capacitor in series with the start winding. This mfd value is much higher than for a motor designed as cap start, but over the years and many motors for many uses, I've found best results with this value. 400mfd per 1/4 hp. That means that a 1/2 hp 120volt motor could be converted with 800mfd. Or 1/8hp as found in older freezer compressors, 200mfd. Makes a truly HUGE difference in ease and quickness of starting. Another thing, these piston pumps typically serve a family for a decade or more before any maintenance is required. The one I have is circa 1950 and over the decades it's pumped probably over two million gallons of water in it's almost continuous family service over more than half a century. After changing the leather cups on the piston, and putting in new rubber valves, which is done about every 10 years, it operates just like brand new. They don't make many things like that any more.
    Hope this may give you some food for thought.
  • Ralph DayRalph Day Posts: 839Solar Expert ✭✭✭
    Re: Small cabin DC water pump set-up?

    Hi Wayne
    Did you miss the recent flooding?

    You guys and your bulletproof appliances! I would like to try a piston pump again, but the only one I tried leaked on the basement floor.

    See Tony's washing machine post here:

    http://forum.solar-electric.com/showthread.php?p=66041&highlight=maytag+gas+powered+washing+machine#post66041

    Sometimes you just luck out!

    Ralph
  • waynefromnscanadawaynefromnscanada Posts: 3,009Solar Expert ✭✭✭✭
    Re: Small cabin DC water pump set-up?

    Ah Ralph, I was VERY lucky this last storm, while other parts of the Province got 6 or more inches of rain, I only got a wee bit over an inch, just enough to keep my micro-mini turbine running in the brook.
    Yes, the unfortunate part of piston pumps is the almost constant, even if slow drip from between the packing and the piston rod. Just the nature of the animal. But again I'm lucky, the pump I have is not only a twin cylinder model, it's gear driven instead of belt, AND, the manufacturer, with great foresight, designed in a kind of cup, directly under where the drip would be, and provided a threaded drain hole for it. So, I have a drain hose that takes care of the drop and the whole thing stays dry and nice as could be. The only piston pump I've ever seen that way. My grandfather had it first, and it just kept being handed down. I'm the 3'rd generation to have and use it. Others pretty much have to have a tray of some sort to collect any drip, unless it's in an area where a bit of wet doesn't matter.
  • HairfarmHairfarm Posts: 208Solar Expert
    Re: Small cabin DC water pump set-up?

    Wayne:
    Hope this may give you some food for thought.

    Yeah, that was definitely some food for thought...more like a six course meal! Thanks for all of the great info. I will probably design a system that involves three pumps inline, one will be DC for everyday use and the other AC (both in the cabin next to pressure tank) for emergencies (no Sun, breakdown of primary DC pump etc.) and a submersible DC well pump that will be dug close to the cabin. I will definitely research the 800mfd option (where can I get more info about this?) because I have a 1/2hp AC pump that has a start up surge of over 3000 watts, although I plan to check it with a Killawatt next time I'm out at the cabin to see the real number. Still, I'll probably find a pump with a soft start feature as SCharles suggested.
    Btw, why even keep the unused submersable in line anymore, as a backup?


    Dwh:
    PV->charge controller->battery<->inverter/charger<-generator

    Thanks for clarifying. This is what I suspected. I will definitely need an inverter that has a charge-through feature. What model do you use?

    SCharles:
    I understand now why your set up works best for you. It sounds like you have an abundance of battery power and a robust inverter that can handle your soft start AC well pump. When I have my well dug, I will try to have it as close to the cabin as possible so that I can use a DC submersable pump. In the cabin, I'll have two pumps in-line separated by high quality ball valves. Both a DC and a soft start AC pump will be inline. The primary will be the DC pump and the AC will be for emergencies like no sun, breakdown of primary etc. Thanks for the great info in your posts. It really helps me clarify a strategy.


    FYI, in fact I plan to "print" this complete post to a PDF file to be later printed out and added to my ever-growing off-grid notebook in the "expensive-crap-I-gotta-buy" section ;)


    Hairfarm
  • waynefromnscanadawaynefromnscanada Posts: 3,009Solar Expert ✭✭✭✭
    Re: Small cabin DC water pump set-up?

    Hairfarm, do you know for sure that your 1/2 hp AC pump is not already Capacitor start? It may well not be, but I'm assuming it's a jet type pump, and if so, it will run at ~3400RPM, which means it has to overcome a lot of inertia getting up to speed, so there will be substantial surge anyway. I've never really measured the surge on jet pumps, just listened to the speed at which they come up to speed, and taking note of how they dim the lights in peoples houses as they do. If the motor has a tubular lump, about an inch and a half across, by 4 or 6 inches long on it's top, or side, then most likely it's already capacitor start, if no "lump" than likely it's not. Where to get the start capacitor/s, you should be able to pick them up at any motor repair shop, and perhaps at some electrical supply outlets. Re the 800 mfd, if one that size isn't readily available at a reasonable price, you can use two, of 400 mfd each, wired in parallel, or 4 of 200 mfd each, or whatever is needed to add up to 800. Just be sure they are rated for at least 110 VAC. You can go higher, but not lower with the voltage rating. I find that 400mfd is quite common, while 800 perhaps not so much.
    Yes, I kept the submersible as backup, and not being sure at the time how my renewable system would hold up to the load. Turns out, there's no problem at all. I really don't need the sub pump any more, as I have a second piston pump ready to go if this one quits. Just kept it there in case of some unforeseen problem at the time, but now it's a real pain in the butt to get it out. Easier to leave it there. lol
    And yes, soft start can be awesome. I modified both my fridge ( a converted upright Energy Star rated freezer) and also my chest freezer, to be very soft start, after which they both have been running on a single SureSine 300 watt inverter for over two years. They're wired through a relay that prevents both operating at the same time, and their thermostats also, through a relay, operate as a remote switch for the inverter, so the only time the inverter is on, is when either of the two are calling for their compressor to run. And the fridge always has priority. Only problem I've had is that the SureSine inverter is designed to shut down when the input voltage exceeds 15, and on very cold but sunny winter days, the solar charge controller will sometimes push the battery voltage a wee bit over 15, which shuts down the inverter till the voltage drops to a more comfortable level.
    Good luck.
  • HairfarmHairfarm Posts: 208Solar Expert
    Re: Small cabin DC water pump set-up?
    Hairfarm, do you know for sure that your 1/2 hp AC pump is not already Capacitor start?

    Here is the pump that I have:
    http://www.sitnsail.com/hairfarm/FP745.pdf

    I don't see a capacitor start anywhere in the manual. You said that you converted your fridge to be soft start. Since I'm not "electrically-minded" can you possible send me a link to more info about this process. I'll need an electrician to set this up for me I think. My 1/2 hp Flotec motor would need an 800mfd (micro farads?) kit according to your post. How much would this conversion/kit reduce my current 3300watt surge to? Or maybe I'm just over thinking and should use my gas gen to power my 1/2 hp AC pump if an emergency arises.

    I probably should have asked these many questions before I bought my shallow well jet pump. It's a great pump...as long as I have lots of AC power. But I can hear my gen (with a 6500watt surge and 5000watt normal capacity) slow down when the pump kicks in. But it does fill my 80gal (30 gal water capacity) PT in about 2 minutes when the pressure switch kicks in.

    My main goal is to be independent of fuel some day so I guess I'll have to ditch the Flotec and get a lower HP motor or a lower capacity DC pump like the one that BB suggested that can run off of a windmill and pv. For the time being It's nice to have the PT filled up so quickly though with the Flotec.

    Now I'm wondering if I should go 24v instead of 12v

    That said, is this a good rule of thumb?:

    12V 1,000W max
    24V 2,000W max
    48V 4,000W max
    Otherwise, the battery cables become as thick as a garden hose, and the batteries internal resistance limits the power output?


    thanks,
  • waynefromnscanadawaynefromnscanada Posts: 3,009Solar Expert ✭✭✭✭
    Re: Small cabin DC water pump set-up?

    Judging from the picture of your pump, it's not capacitor start. The capacitor I doubt you will find as part of a kit. You should however be able to pick up a couple of 400 mfd caps at a motor repair shop, and you would have to wire them in yourself, of get some familiar with motors to do it for you. As mentioned earlier, the two 400 mfd caps are wired in parallel, then the resulting capacitor "package" is wired in series with the start winding. How much it will reduce the start surge is something you will find out after the fact, but from personal experience, that surge will be at least cut in half.
    As to what I did with my fridge and freezer, this was not a kit either. I have many years/decades of past experience with this kind of thing, so made the changes myself. Again a start capacitor makes a huge difference and there's no way the 300 watt inverter could even begin to budge the compressor without it. The whole starter electrics have been modified and changed. You'd nave to be familiar with such things to grasp what was done, but put as simply as I can, during start, a step down transformer is used to drop the voltage from the inverter from 110 to about 95, which boosts the available current from the little 300 watt inverter. That along with capacitor start, gets the compressor pretty much up to speed in under one second, at which time the timed start relay kicks out, cutting power through the start capacitor (leaving the run cap in circuit if it has one) and at the same time releases a second relay which takes the step down xformer out of the circuit and connects the load directly to the inverter for full voltage. The compressor then runs just fine on the little SureSine 300. I've actually done this to two freezers, and two other freezers which had been converted for fridge use. The first one was done probably 8 years ago and is still doing it's thing just fine. The latest, an upright freezer converted to fridge, just a couple of months ago. This last one was energy star to begin with, and is the easiest of all for the little inverter to start, but is very sensitive to the value of the start capacitor. Since these compressors were not designed as capacitor start, I had to do a bit of experimenting to find the capacitor value that worked best. The old freezers worked best with 200 mfd. The first fridge conversion, started best with I think 170, and the latest one, which is also capacitor run, started best with an 85 MFD cap. I realize this may seem as complicated as heck, but it's what I had to work with, so I either made the changes, or went without. I'm very fortunate and thankful to be able to do such things, but unfortunately sometimes take that ability for granted because I've been doing it all my life, at least since the age of 12, and I'm now far from a kid. Hopefully some of this will be food for thought for someone at least.
    Peace.
  • HairfarmHairfarm Posts: 208Solar Expert
    Re: Small cabin DC water pump set-up?

    Thanks for the great input Wayne. I'll talk to my electrical contractor buddy about your set-up. I have a pretty good idea now of the direction I need to go in with scalability in mind. I don't want to install a system that will be outdated in two years, or that I can't build upon.

    As far as my location is concerned, it's a funny kind of place, the temperature ranges from 112 degrees in the summer to 28 degress at night in the winter. High desert area. I bought the cabin after experiencing the stars there for the first time.

    Hairfarm
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