Propane hot water heater location--rendering

Discussion in 'Boat Design' started by rsimon, Jun 12, 2011.

  1. rsimon
    Joined: Jun 2011
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    Location: Land locked Florida

    rsimon Junior Member

    The plan is to locate the propane hot water heater/burner unit OUTSIDE of the boat in a separate vented locker to protect somewhat from the elements (red square.) The main reason is to eliminate any dangers of fume build-up though. Propane tanks are to be located in it's own locker on shelfs off the stern as shown.
    http://s1216.photobucket.com/albums/dd377/projecthouseboat/?action=view&current=f557792d.jpg

    The hard propane line is to travel from Propane tanks/locker under shelf via a bulkhead gas-line fitting thru the transom, then running along the interior then punching out briefly (using a bulkhead fitting) to feed the Propane burner which is itself outside attached to the side of the superstructure. Would a surveyor have a problem with this? I don't think having a square box sort of protruding off the side of the superstructure would look TOO bad, considering the peace of mind and safety's sake. I'm still debating going with a hybrid electric/propane water heater.
    Check out the project of a lifetime: http://s1216.photobucket.com/albums/dd377/projecthouseboat/
    Thanks in advance for any responses, unless they're insults that is.
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    As a surveyor I would have a problem unless you have a warning sign that the blower must be run 5 minutes before and during operation of the heater. Propane gas like gasoline fumes is denser than air.
     
  3. rsimon
    Joined: Jun 2011
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    Location: Land locked Florida

    rsimon Junior Member

    Venting of propane burner

    My burner is located OUTSIDE of the boat, why would I still need venting or use of a blower for that matter?
     
  4. gonzo
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    Location: Milwaukee, WI

    gonzo Senior Member

    I interpreted the drawing as the heater being inside the cabin. If everything is outside, I don't see any danger.
     
  5. Mark Cat
    Joined: Jun 2011
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    Location: Michigan

    Mark Cat Senior Member

    Best to follow ABYC A-26 for this installation.

    The Vented locker must have a drain. Good to provide locker warning labels for non-smoking and emergency shut down (if not automatic through an electric valve) . Heater exhaust must be located away from fuel tank fill or vent by 20 inches, and not be positioned such that exhaust can enter into the cabin.

    Many surveyors will be looking for a CO monitor in the cabin in case underway there is an exhaust blowback stationwagon effect to the installation.

    Best to review the ABYC standards for a comprehensive list of the different system interactions and how this may influence a surveyor for an LPG appliance installation.

    Mark
     
  6. keysdisease
    Joined: Mar 2006
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    Location: South Florida USA

    keysdisease Senior Member

    The hard line runs inside the boat. Why don't you dump this idea and go with a traditional heat exchanger / electric water heater. They work very well and are safer and I'll bet cheaper than all this propane stuff your doing.


    Now for cooking, there are approved methods for propane. I had an electric solenoid valve on my propane bottles with switch in galley. When you were through cooking you left burner on and flipped switch. If burner went out you knew valve closed. Tanks were in vented compartment under seats on flybridge.

    Steve

     
  7. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Propane is a hard choice for instant hot water .

    It frequently has to be carried in the dink in 20# bottles as a good sized built in tank has almost no place to be refilled dockside.

    Take a look at the BTU input requirements , frequently 75,000 to 90,000 btu while on. There are about 90,000btu in a gallon , so that's 4 hours of hot water per dink trip.

    For cooking or refrigeration Propane is an excellent choice m, for HW ????

    AN RV hot water unit is 120V as well as slow propane (heats 6 or 10 gal) and is far better if dish washing , not just showers are needed.

    A final hassle with instant HW propane is water flow is required to have the burner operate.
    So the temperature is hard to stabelize in a shower.

    Simplest solution is a 1 1/2 return in the shower , so the hand held spray can stay on , keeping constant temps , the water is simply returned to the Fresh water tank. This does cost propane to heat the un used water.

    FF
     
  8. philSweet
    Joined: May 2008
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    FF is right. Most on demand types require a large flow rate to trigger. Usually more than what you want to use on a boat. Any attempt to conserve water will interfere with its operation. If operating a household unit off a demand pump, you will almost certainly have to rework the unit's control system.
     
  9. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    You know I was thinking about this, and while the flow rate is a problem I think it is solvable without trying to heat the entire boats water supply. The problem however is that the plumbing to get it to work would be pretty massive. You would just have to install a bypass system that shunts extra water to an accumulator tank after the shower head. As the water level in the say 5 gallon tank lowers more water would be pumped in from the standard holding tank...
    This conceptually seems to work, though it would be expensive and require lots of additional pumps, plumbing lines, tanks, and maintenance.

    What about a simple diesel fired space heater with copper coils stacked inside the chamber. It should get plenty hot, and you likely will already have diesel onboard.
     
  10. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    "You would just have to install a bypass system that shunts extra water to an accumulator tank after the shower head. "

    The use of a standard house tub/shower unit already does better.

    Simply select the TUB supply water to return to the FW tank with a valve..

    Close the valve , the shower will work , just like home.

    FF
     
  11. rsimon
    Joined: Jun 2011
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    Location: Land locked Florida

    rsimon Junior Member

    Response to various responses

    Wow, thank you all so much for responding, I had no excuse for not getting a computer until recently...sure would have saved myself a lot of hassles if I would have been able to get onto this forum 4 or 5 yrs ago when I first started the rebuild houseboat project. The kind of responses is exactly what I had hoped for: a combination of great ideas from true craftsman, honest criticisms and thoughts from adept pro's. Keep them coming. I really should have a better rendering though.
    To clarify: the boat is going to be located behind my own home which is actually a boat house on stilts on the edge of a lake with a dock.
    The boat may be out and actually lived on for months at a time without access to "real" shore power, hence the choice for propane (ie. access to hot water without needing power.) Fresh water though will be plentiful at the dock. "Scrapping the 'propane stuff' idea" is probably not going to happen ...at least yet. The Houseboat (34' Marinette Rivercruiser) does not have the inboard motor (so heat exchanger via motor to heat water will not be an option.) I am adapting an outboard motor bracket so boat is to be powered via outboard(separate issue-updated pics on that forthcoming.)
    I still have not ruled out Propane/electric w/ accumulator tank though.
    I've been asking around and perusing other forums, and the tankless hot water heater appears to be appreciated and well talked about.
    The various tankless heaters I've been looking at:
    http://precisiontemp.com/pt_rvmd_m500.html
    http://www.excelonlinestore.com/servlet/the-Gas-Appliances/Categories
    http://boschhotwater.com/StartPage/...eries/FeaturesandSpecs/tabid/346/Default.aspx
    http://www.sportsmansguide.com/net/...er KW Box&s=&a=browse&k=tankless water heater
    All do have a minimum required flow rate as a threshold to operate, which my on board pump should provide, but it is something I didn't think of--that I would have to run the shower at a high enough flow rate that will allow the burner to turn on. The safety issues that have come up are things that I'm going to apply as well ie. A unit with "no pilot light" so-called flameless burner, Emerg. shut-off selenoid (flame failure device and or oxygen depletion sensor.) Of course co and propane sniffer/detectors. Propane locker will be sealed and labeled except for vent/drain at lowest part.
    The one concern I can see based on something Mark Cat said was the wafting of fumes (or station wagon effect.) The heater/burner unit that will be attached to the OUTSIDE of the structure will in-turn be enclosed in a vented/weather proofed box, but still...fumes would be present...with windows on either side. Could I simply make a flume or chimney that vents fumes up and over and away? That fume issue could be a project stopper there: http://i1216.photobucket.com/albums/dd377/projecthouseboat/f557792d.jpg
    http://i1216.photobucket.com/albums/dd377/projecthouseboat/99d98a56.jpg
    Alternatively, I could locate the whole burner with chimney/vent in the engine compartment where there is room for it and the propane lines would be shorter runs, but the idea of all that in an enclosed space INSIDE the boat is worrisome, but not ruled out. I will look into the BTU numbers and savings comparisons as you suggest. These are all things that I didn't think about so thanks so much. Anymore suggestions are welcomed.
    For the surveyors: Even with the burner unit being OUTSIDE of the structure, will venting the fumes up and over the top of the roof be acceptable to prevent the "station wagon effect?" and how does the surveyor judge how much fumes flowing out in the air and possibly entering the cabin acceptable? Do you use some fume detector or experience.
    Thanks so much all.
     
  12. Saildude
    Joined: Jun 2011
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    Location: Seattle, Washington, USA

    Saildude Junior Member

    Propane is heavier than air, so any "over the roof" would be an exhaust vent - seems to me that your bottom vent would best to go down to deck level or best overboard so the propane could not sneak in through a deck fitting.

    The propane is heavier than air is why propane lockers are required to vent overboard and the numerous rules that don't allow joints in propane lines, remote shutoffs etc. It is also why some people are going to CNG (compressed natural gas) because the CNG is lighter than air and will not collect in the bilge in case of a leak.
     

  13. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Sounds like you could contemplate a solar setup.

    These can be home brew with electric back up if desired.

    A properly sized unit only requires the HW heater (which works as a holding tank) be slightly larger than normal.

    A tiny circ pump, which can be solar powered moves the hot water down to the tank, controlled by a thermostat.

    Home Power magazine is a fantastic source for dozens of system designs, in every price range.

    FF
     
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