pressure tank size?

summitdweller
summitdweller Solar Expert Posts: 28 ✭
in Solar Water Pumping #1
I have an off grid fifth wheel with a structure around it and what to pull out the fifth wheel and enclose it all but in doing that I lose all the water/propane/dc properties. My question is how big of a pressure tank for the water and a small pump do I need? I am 1 person and maybe one at most shower and dishes etc a day some day would like a front load washer. Holding tank (300 gallon) is level with structure. Distance to any water oulet in struture would be at most 25 feet and all at same level would also like to get tankless water heater found a Paloma ph-5 is that any good? Thank you. Have 2 130watt kyoceras and 200ah batteries and a honda 2000i genertor. Working on getting more but money is tight.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
    Re: pressure tank size?

    Bottom line is install the largest tank you can fit/afford. Keeping your pump cycling to a minimum prolongs pump life, and a large tank will allow you draw considerable water without running the pump. I would suggest a ~50 gallon. (They come in strange ratings with gallon equivalents).

    The Ph5 Paloma is out of production and parts are getting hard to find. Ph6/12 are also out of production but just recently and parts are commonly available. The PH5 has a tiny little capacity. If you have very cold incoming water, you may not be able to get a good shower. A Ph 6 will give a good shower with 34f incoming water.

    As for a pump, what are you pumping from? Lake, creek, well, cistern?

    Tony
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  • summitdweller
    summitdweller Solar Expert Posts: 28 ✭
    #3
    Re: pressure tank size?

    I pump from a creek using a gasoline honda pump to the water tank. Yes the water is cold especially in the winter. If you are saying 50 gallon (so actual tank is twice that or something?) that means I would have 50 gallons of pressurized water before the pump has to come back on? Can I work it so the pump runs during the day only? Via a switch or something or would I just have to use the bulk of the water in the day?
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #4
    Re: pressure tank size?

    Let's start with the easy one first. When you pump water into a pressure tank, and pump the pressure up to say 50 psi, the water is then pushed back out of the tank by the force of that pressure. So once you pump it up, the water can be drawn down as needed, and the water will flow as long as there is pressure in the tank.

    The way this works is quite simple. As you fill the tank, there is a static volume of air at the top of the tank, as the water fills the tank, this air gets compressed. It is this compressed air pressure that forces the water back out the pipe. Modern pressure tanks capture the static air in a bladder so that the air never gets introduced into the water, causing other problems.

    Now filling a pressure tank from a gasoline pump is do-able, but it is unusual. The way most pump systems work, is there is a pressure switch on the tank that cuts in at a predetermined low pressure (~20-30 psi typically) and a predetermined cut out pressure (40-60 psi) So in simple terms the switch turns the pump on and off as needed.

    If you are going to do it with a gasoline pump you will probably not be able to fabricate an auto start/stop system for your pump without spending way too much money. Your gas pump will have to be able to pump to pressures that are useable (30-50 psi) which equates to the ability of a pump to pump to about 100' of head, including any lift from the creek to the tank. So you will be looking for a high head, low volume pump.

    The way that I would do it, is I think I would add a pressure relieve valve to the tank (required anyway) that is set at the maximum pressure that you would like, some where ~60 psi. Start the pump, and when the Pressure relief pops, you are as full as you should be. Stop the pump, and the Pressure relieve should close, leaving the tank full. (Make sure you vent the relieve valve outside!)

    I'm sure there are pressure switches/clutches that you can get for mechanical pumps, but I think they are going to be expensive. So you could pump water once a day or as often as needed. If you find that you use more water than one tankfull per day, there is no reason that you can't add a second tank, plumbed into the system, doubling the volume.

    Another option would be to do some sort of gravity tank that is filled by gas pump, and then install a small pressure pump/tank system that runs on PV or battery to pressurize the house.

    Other issues that I see are how are you going to ensure that your water is potable if you are going to draw from a creek? Chlorinator/UV system?

    Tony
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  • summitdweller
    summitdweller Solar Expert Posts: 28 ✭
    #5
    Re: pressure tank size?

    Sorry the honda pump is for filling the water tank from there a llittle gravity to a new 12vdc pump to fill the pressure tank hopefully with a switch. As for potable I filter drinking water seperately after the fact, showers and dishes can use (in my world) any water.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #6
    Re: pressure tank size?

    I would look here:http://www.shurflo.com/

    Shurflo makes a variety of pumps that will pump from 25' into 60 psi tanks. Most of these pumps will push water much farther than the will pull water. Since you have gravity you are one step ahead.

    Depending on where you are, you have to consider freeze protection issues as well.

    Tony
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  • summitdweller
    summitdweller Solar Expert Posts: 28 ✭
    #7
    Re: pressure tank size?

    Okay I know it has been awhile but I got 2 Big pressure tanks for free and am still looking at the paloma ph5 different source you say it does not heat very cold water to a good shower temperture how much of a temperture increase does it reasonable do? Other question way off track but do you need/want a pure sine inverter for a refrigerator or would a msw work? How about an older front load washer msw or pure? What size inverter?

    Thanks
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
    Re: pressure tank size?

    As for the PH5. These have not been made for a number of years, and have a fairly low BTU rating. My favorite PH6 will take 34f water and produce a very good, very hot shower. These were discontinued a year or two age, but you sometimes see the on EBay.

    As for the inverters,, any motor load is much happier with TSW. You will draw more current and shorten the life of the motor with MSW generally. You are going to need a pretty good sized inverter to power a frige,, bigger for a washing machine.

    Icarus
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: pressure tank size?

    Icarus will know the info on the tankless, but I can probably handle the inverter questions. :D

    Stay away from MSW inverters if you want to run refrigerators, washing machines, or anything like that (AC induction motor). Yes, it might work but it will draw more power and shorten the appliance life.

    What's more, these things have big start-up surges. Even though a refrigerator might draw 130 Watts running, the same one might demand roughly 1000 Watts just for a moment to get started. Likewise with the washer. Also, a 'frige which is "frost free" will have a heating element that comes on periodically - usually taking 500 Watts. A thread on the notorious power demands of refrigerators: http://forum.solar-electric.com/showthread.php?12272-Just-how-bad-a-small-frige-is

    If you have the 'frige/washer you want to run you can power it through Kill-A-Watt and get an idea how much it will use, but this will not show the start-up surge. Don't rely on "surge ratings" for inverters to cover this as they are often optimistic (rated under ideal conditions). Also, the battery bank has to be able to stand this sudden demand for power.

    For most refrigerators you'll need a 1 kW true sine inverter or larger to handle the start-up. A washing machine cn be worse than this, as the 'frige will typically have a 1/4 HP motor whereas the washer will have a 1/3 HP high-torque motor. They can be very nasty on power consumption.

    Hmm. Maybe I should start testing some washers and see what we get. :roll:
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  • summitdweller
    summitdweller Solar Expert Posts: 28 ✭
    #10
    Re: pressure tank size?

    So what size inverter do you recommend for a washer/fridge? I am about to go to 24v and double my current system so I will need a new inverter anyway. After I get the fridge and a washer I do not see any other big appliances in my future.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #11
    Re: pressure tank size?

    If you are going to run one at a time (turn off fridge to run washer), you probably need a minimum of 1,500 watts for the inverter to reliably start/run everything (assuming reasonably recent vintage of Energy Star refrigerator of 20-25 cuft maximum size).

    If you are thinking of purchasing from our host, you should give them a call and ask. Different inverter brands have different amount of surge current support.

    Have you used a Kill-a-Watt or similar to measure your loads (the kill-a-watt will not give accurate surge numbers as it takes ~1 sample per second)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #12
    Re: pressure tank size?
    summitdweller wrote: »
    So what size inverter do you recommend for a washer/fridge? I am about to go to 24v and double my current system so I will need a new inverter anyway. After I get the fridge and a washer I do not see any other big appliances in my future.

    It's a good idea to go up to 24 Volts if you're planning to run heavy draws, as it cuts the current draw in half and makes it much easier on the batteries & wiring. A 2kW inverter would definitely handle it (think of it like this: a normal household outlet is 15 Amps @ 120 Volts or 1800 Watts). The downside is that big inverters use big power for themselves - like 23 Watts just doing nothing. The good ones can be set in a "standby" mode which reduces the power consumption to about 6 Watts (numbers pulled from Outback equipment) until it senses a load and ramps up to full power.

    In my opinion the Outback line is the best choice if you need full system integration (charge controller(s) and inverter(s)) but gets pricey.

    Magnum makes some very good inverters (not integrated) around 4 kW @ 24 Volt. Either of these are in the $2,000 range.

    The least expensive choice that would work is probably the Exeltech XP1100-24. That should be just enough power to start either and is only about $600. But it does not integrate and does not have a standby mode.

    Others here may have some additional suggestions. You should read through NAWS Inverter Selection info here: http://www.windsun.com/Inverters/Inverter_selection.htm
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #13
    Re: pressure tank size?
    Cariboocoot wrote: »
    It's a good idea to go up to 24 Volts if you're planning to run heavy draws, as it cuts the current draw in half and makes it much easier on the batteries & wiring.

    Wish I had gone 24 volts now, after the fact. But I never dreamed my system would grow to run the whole house, rather I thought it would only run a few small things. Thus I started with 12 volts and it stayed 12 volts because of the high cost of changing everything over. :cry:
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #14
    Re: pressure tank size?

    Xantrex has a 4000w 24V inverter http://www.solar-electric.com/xaxwhyin.html model XW4024 which has a huge beefy transformer, generous surge specs, and gives 240VAC if you need that.
    A fair amount of overkill for just 1 fridge, but it's efficiency is a high 90-94% (94% at light loads)

    Also has a 150A battery charger, transfer switch, and 2 ac inputs (Grid & Genset) that it will autoswitch between.

    Nearly all the comforts of home!
    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 ,

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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #15
    Re: pressure tank size?
    mike90045 wrote: »
    Xantrex has a 4000w 24V inverter http://www.solar-electric.com/xaxwhyin.html model XW4024 which has a huge beefy transformer, generous surge specs, and gives 240VAC if you need that.
    A fair amount of overkill for just 1 fridge, but it's efficiency is a high 90-94% (94% at light loads)

    Also has a 150A battery charger, transfer switch, and 2 ac inputs (Grid & Genset) that it will autoswitch between.

    Nearly all the comforts of home!

    may be too much overkill as he'd need far more than just a doubling of his battery bank just to overcome the high ripple of the inverter.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #16
    Re: pressure tank size?
    niel wrote: »
    may be too much overkill as he'd need far more than just a doubling of his battery bank just to overcome the high ripple of the inverter.


    You are correct, if the inverter is fully loaded, it needs the large battery bank, you only have high ripple (DC current peaks), if you have high loads.

    For surge starting appliances, it would not even blink.

    And you have the dual AC in, transfer switch and charger too ! But it's pricey. I'm not familar with the Outbacks, if they have the same features.

    And everyone knows, loads grow, so IF that did happen, when batteries need to be replaced, it's a chance to upgrade them too.
    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 ,

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