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Home Forums Technical Discussion low pressure, no electricity hot water

This topic contains 9 replies, has 8 voices, and was last updated by  Jim 5 years, 7 months ago.

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  • #36892

    gravy
    Participant

    I have no electricity, a large propane tank and water from a well. I have a water tank for storage in the loft which gravity feeds a sink and toilet. I would like to have hot water. Tankless heaters require more pressure than I can deliver.

    Can I use an off the shelf small propane fired hot water heater that will work on the 3 or 4 psi I can deliver?

    #41721

    elnav
    Member

    Modify the design to be gravity feed. I had a gravity fed water heater in my boat that was 30 years old and still functionl when I got it. Usually its a pressure senssor that stops water fflow if pressure goes low. The idea being if low pressue results in low flow which would end up getting too hot then it shuts off water entirely. Change design so only high temp will shut off gas nd allow water flow regardless. Only downside is cold water if gas is shut off.

    #41723

    caverdude
    Participant

    A friend of mine once used a coil of black pipe on his roof, you can be amazed at how hot it can get.

    http://larrydgray.net

    http://larrydgray.wordpress.com

    #41734

    elnav
    Member

    This is an excellent example of the other kind of solar power I mentioned in a thread. Solar thermal is roughly 3X as effective as solar PV in extracting energy from sunlight.

    Although we have all heard about it, somehow it’s not near the top of the priority list when it comes to off grid housing. Concentrated sunlight has many uses. Although a bit more comple, storage of the heat from sunlight is posible. For low pressure water flow, you pretty much need to have a gravity feed.

    Concentrated sunlight using lenses or mirrors are being used industrially to heat water into steam which opens up endless possibilities. Steampowwer can drive pumps and generators. Unfortunately most of this kind of development is currently being done in Europe or India.

    #41742

    Brie217
    Participant
    #41958

    Garrett
    Participant

    But sun power can be used in area where the day is long and sun is more active. In north regions it is hardly possible.

    #41959

    gordo
    Participant

    jabsco makes a 12v pump about the size of a chicken leg that is use to preasure water in rv from holing tank to fixture. may be model 42510-0000? about 12 watts in draw use with 2amp breaker and switch turn pump on when in shower.

    #42022

    Dillinger
    Participant

    Hey caverdude.

    I use this method and as we have plenty of sun … it is great in the day.

    There is a downside though. The water goes cold at night and of course that means no hot water in the morning. I run an Eco resort in the Caribbean and we are completely off grid. My guests say the same thing …. no hot water at night/morning is the only thing we are not doing right.

    So anyone? Can you help me add a tank or whatever to store the hot water?

    I know … buy a solar water heater with tank …. but nothing on this island … and import duty make it all VERY expensive.

    Any way to add a hot water storage tank?

    To recap. I use a 1 1/2 inch black irrigation hose on the roof and that feeds the hot water input to a normal shower set up. I have about 15-20 psi water pressure gravity fed. I need hot water storage added. Any help would improve Eco resorts 500%.

    Thanks.

    #42028

    elnav
    Member

    INSULATION – lots of it. Store hot water from previous day sun heating. Remember the more mass volume in round tanks the better.

    Although it is a nuisance also consider using a rocket stove to preheat stored water to higher temps. Yes it does mean getting up earlier than the guests but isn’t that the nature of being in the service/hospitality business?

    If you store the water in roof tanks a rocket stove on same level puts it outside the building thus less fire hazard and a chimney is no problem. Circulating water horizontalluy will be a thermo syphon so no pumping involved.

    #42053

    Jim
    Participant

    I use solar water heater (my own design) in warmer months when it’s most efficient and small propane water heater salvaged from R.V. in winter months. Costs nothing in Summer and very little in Winter. Both fed with same low pressure gravity flow system. Works well for me.

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