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  • DHW on propane

    Looking for some recommendations on DHW with propane fuel. Currently run cabin on propane generator, EU2000. Current DHW is 30 gallon 120 volt. We have to run 5kw gen set to operate. Cabin is used 9 months with visits 3 -10 days. Location is Upper Pennisula of Michigan. Smallest tank type is 40 gallon. Anyone have any reviews for on demand type? Our usage is light, no laundry, or dishwasher. Just a few showers and hand wash dishes. Water from well is hard.
    Thanks

  • #2
    You are a perfect candidate for Tankless. Rheem and EcoTemp are the two I would suggest. Just make sure if you buy one is a model made for LPG and not NG which in practice is the pressure regulator. LPG has a higher BTU content and if not accounted for would burn up the burner and possible explosion.

    Tankless only uses gas when you turn the faucet on. When you are not there just turn the valve off.
    Last edited by Sunking; 01-14-2017, 09:11 PM.
    MSEE, PE

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    • #3
      If you can still get them, Eternal Tankless give the best of both worlds. internal 1 gal tank prevents hot/cold surge and multi-stage burners.

      Tankless have huge BTU demand and need large gas supply lines (and large regulator to supply it) They have a minimum flow rate before the burner lites, and a max temp rise for specific flow rates. So you could be in the shower, someone else turns on hot water , and you loose 30 degrees of temperature.

      I preheat before the the tankless with solar heater on the roof, or wood stove thermosiphon tank.
      Powerfab top of pole PV mount (2) | 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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      • #4
        Originally posted by Mike90250 View Post
        If you can still get them, Eternal Tankless give the best of both worlds. internal 1 gal tank prevents hot/cold surge and multi-stage burners.

        Tankless have huge BTU demand and need large gas supply lines (and large regulator to supply it) They have a minimum flow rate before the burner lites, and a max temp rise for specific flow rates. So you could be in the shower, someone else turns on hot water , and you loose 30 degrees of temperature.

        I preheat before the the tankless with solar heater on the roof, or wood stove thermosiphon tank.
        There are also tankless with a controlable orifice for water flow as part of the unit.
        If mine is operating at full set temp with the burner full on and you open another valve the flow through both outlets is limited to the original flow rate.
        One kind of interesting side effect is that if, after some time in the off state you open a hot water valve the water will flow slowly for a couple of seconds while the burner heats up and the will jump to full flow.
        The part that usually gets changed when converting any heating appliance between natural gas and propane is the orifice that controls gas flow into the burner.
        The pressure regulation is usually done externally to the appliance and there is no additional regulation down before the orifice.
        The recommended pressure for LPG is, I believe, about 10-11" WC, while natural gas is more like 7" WC.
        When I added a gas dryer to my existing LPG system (furnace and tankless), the plumber told me that they could either dig up my 3/4" main from the propane tank to the house and replace it with 1" or put a high pressure (~2PSI) regulator at the tank output and two low pressure regulators at the house end, one for the furnace and dryer and one for the tankless. The higher pressure in the long line allowed a higher bulk flow rate for the same size line.
        SunnyBoy 3000 US, 18 BP Solar 175B panels.

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        • #5
          Originally posted by Mike90250 View Post
          So you could be in the shower, someone else turns on hot water , and you loose 30 degrees of temperature.
          Well that still happens today, mabey not 30 degrees but I remember the days before anti-scald shower heads. if someone flushed the toilet, you got a blast of hot water, and vice versa.
          MSEE, PE

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          • #6
            There are small, inexpensive instant water heaters available. Sounds like your needs are minimal and these might be an affordable answer. I have been using one on my RV for over 10 years without the slightest glitch. Its propane requirements are easily met by a 20# tank of propane with the supplied hose regulator. This particular unit is probably the smallest, least expensive one made. There are higher capacity models available which are still very affordable. We have a middle of the road Bosch version in Baja that, again, is rock solid. This one has pretty salty brackish water running through it and hasn't complained yet. it's over 10 years old. You can find a dizzying array of them on eBay if you want to compare .
            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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            • #7
              Originally posted by Sunking View Post

              Well that still happens today, mabey not 30 degrees but I remember the days before anti-scald shower heads. if someone flushed the toilet, you got a blast of hot water, and vice versa.
              That was much more of a problem back when it was common to run DWH above 145F. The comfortable mix required a lot of cold water in the mix and so was very vulnerable to cold water pressure.

              I run my tankless at 120F during the summer and 125F during the winter and do not have to add much cold water at all.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

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              • #8
                Andy I do see one problem I just caught. Hard Water is hard on any kind of hot water system. Only thing I really disliked about North TX when I lived there for 13 years. It can completely clog hot water lines, and Tankless Heaters do not play well with hard water. Conventional tanks not a lot better either.

                One thing I had to learn how to do and it is a PIA is disconnect the hot water line from the tank every couple of years, drain the line, fill with agriculture vinegar over night, and then flush the crud out. It works good, but after the 3rd time I gave in and bought a water softener. Worth every penny.

                Not a problem in Panama, it is all rain water soft as a baby butt. Even dry skin issues cleared up and you save a ton of money of soap. Taste a lot better too. If you are in the construction phase leave some room above so you can gravity feed vinegar or CLR to clear hot water pipe(s). Or get a softener or cistern to fill with rain water. .
                Last edited by Sunking; 01-15-2017, 05:06 PM.
                MSEE, PE

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                • #9
                  Originally posted by Sunking View Post
                  Andy I do see one problem I just caught. Hard Water is hard on any kind of hot water system. Only thing I really disliked about North TX when I lived there for 13 years. It can completely clog hot water lines, and Tankless Heaters do not play well with hard water. Conventional tanks not a lot better either.

                  One thing I had to learn how to do and it is a PIA is disconnect the hot water line from the tank every couple of years, drain the line, fill with agriculture vinegar over night, and then flush the crud out. It works good, but after the 3rd time I gave in and bought a water softener. Worth every penny.

                  Not a problem in Panama, it is all rain water soft as a baby butt. Even dry skin issues cleared up and you save a ton of money of soap. Taste a lot better too. If you are in the construction phase leave some room above so you can gravity feed vinegar or CLR to clear hot water pipe(s). Or get a softener or cistern to fill with rain water. .
                  Most if not all tankless heaters specify a periodic flush since the hard water deposits concentrate on the walls of the heating coil.
                  Mine has bypass valves and hose fittings to allow the tankless to be isolated from the water system on both sides and then you gravity feed or pump your cleaning solution through the coil only.

                  Easier and cheaper than the same treatment for a storage tank, but you might have to do it more often.
                  SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                  • #10
                    Originally posted by inetdog View Post

                    Most if not all tankless heaters specify a periodic flush since the hard water deposits concentrate on the walls of the heating coil.
                    Mine has bypass valves and hose fittings to allow the tankless to be isolated from the water system on both sides and then you gravity feed or pump your cleaning solution through the coil only.

                    Easier and cheaper than the same treatment for a storage tank, but you might have to do it more often.
                    That is why I am bringing it to the OP attention so he can take that into account. The more you know...

                    MSEE, PE

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                    • #11
                      There are cleaning/descaling kits available. Seem to be pretty simple to use.
                      http://www.ebay.com/itm/Tankless-Wat...0AAOxy5jxSds2A
                      2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                      • #12
                        Thanks guys, appreciate all advise. Still in planing stage and am using electric currently. Yes I am aware of the hard water, thanks, I have isolated valves on tank and bypass to recirculate CLR with a acid pumpevery few years. Sinking, yes very familiar with cisterns, I spend a few months a year in Nevis as a handy man helping out the brother in law.

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                        • #13
                          Originally posted by Andy Muzik View Post
                          Sinking, yes very familiar with cisterns,
                          I have been called much worse.

                          MSEE, PE

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                          • #14
                            Sorry, dam auto correct and paying to much attention to Packer game. Sunking.

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                            • #15
                              No apology needed, were good. Dam Packers. Oh well they are the Cowgirls again.
                              Last edited by Sunking; 01-15-2017, 10:16 PM.
                              MSEE, PE

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