Hot water, heaters, cookers.....

Discussion in 'Option One' started by Willallison, Jul 11, 2002.

  1. Willallison
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    Willallison Senior Member

    Thought this topic deserved its own thread.......

    With a little ingenuity I think we could engineer O-1 to accept a number of heating / water / cooking alternatives.

    Much has been written about the advantages of using a diesel / parafin etc type of cooker / heater. The biggest problem (apart from cost) with this type of system is that if you also want to use it to produce hot water, then you are stuck with 'having the heater on' at the same time. That's ok if you only cruise when it's cold - but ask Paul if he'd like a furnace running in the corner of his cabin right now......
    I think those systems are terrific for certain applications - so O-1 could be designed to accept such a system.

    For a number of reasons - simplicity, light weight and cost to name just 3 - many would choose to simply use a portable single burner stove, take a portable heater if it looked like being cold, and leave the showers till you get ashore. It should be very easy to ensure O-1 could fit this bill.

    Some would like the instant heat provided by gas (LPG, proane etc). A tankless water heater, cooker and maybe an LPG fueled heater.......
    We'd nee to ensure that O-1 could be built with a suitable storage locker and a few other things - no reason why it couldn't be done.....

    Then there's the mini-live-aboard option which is in the early stages of gestation in my mind....
    A small, lightweight, very quiet petrol engined generator capable of runninging a tankless water heater, or an immersion water heater, a space heater, fridge etc etc etc
    A well insulated locker, a few wires and there it is! No need to call in to the dock 'till it's time to come home.

    Given that O-1 is intended to appeal to a wide variety of people, with a wide variety of needs, wants and opinions, it makes sense to try (where possible and sensible) to appeal to all their requirements.
     
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  2. Willallison
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    Willallison Senior Member

    Alas I must consign myplans for the (almost) self reliant mini cruiser to the scrap heap:(
    A little more research and a little more maths leads me to the conclusion that electricity (courtesy of a small generator) is not the way to go. Assuming you like your showers at around 42C and your water starts off at around 10C then you will need a rise in temp of about 30C (54F). A frugal shower uses about 1 gpm.

    Westmarine offer an electric tankless heater for US$239. When you look at the Eemax site, you see that their most powerful model requires 3.5kW and can produce a heat rise of only 24F at 1gpm. Almost all the other systems I found uses 10's of kW. So you would require a HUGE genset to cope with the power draw. One alternative is to use a smaller generator and run the system via batteries and an inverter. Once again, you would require so much battery capacity, that the weight would be a killer.
    I thought I had found a solution when I came across the Ariston point of use system http://www.electricwaterheaters.com/ariston/index.htm
    but when you look closely, you see that using the 6gallon unit you would need to run a generator for 1/2 an hour for every 5 minute shower....not a very efficient use of power when you can flick the switch and get instant hot water with LPG......

    So, what of all the other advantages of having mains power at your finger tips - like battery charging etc. - well Honda produce a number of little generators which could still be of some use aboard a boat like O-1. Models like this http://www.hondampe.com.au/Hondampe...lt.htm?chan=~hondampe~power~range~generators~ only weigh 13kg.....

    So, for me at least, my first choice would be gas (LPG) - cooker, hw and heating too perhaps. Closely followed by diesel, using something like the Webasto coolant heater http://www.suremarine.com/body.html . Expensive - but good.
     
  3. Portager
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    Portager Senior Member

    ErikG;

    Please don't take this personally, but here is my opinion.

    If you read the article that I provided a link to earlier http://www.uaf.edu/seagrant/boatkeeper/boat-heat.pdf you will see that Terry Johnson says, "Kerosene, white gas, and alcohol portable heaters are sometimes sold for marine use. They are non-vented, and the exhaust is open and introduces water vapor to the living space. If the space is not adequately ventilated this can cause oxygen depletion and carbon monoxide poisoning. These portable heaters have no place on an enclosed boat."

    The reason that so many people choose these options is not because they are safer, but because they are cheaper (and all to often the consumers are uninformed of the safety dangers). One of the main cost differences that separate low cost systems from some higher cost systems is the cost to confining combustion within a combustion chamber and vent the exhaust gases to the outside. The intelligent shopper will study the options and then choose the level of safety they can afford. In my case, I will have a diesel powered boat and I'll use water jacket heat and waste heat from the exhaust for Hydronic heat and a diesel stove. For O-1, my engineering opinion is that Hydronic diesel heat and a diesel stove would be the safest. I am still evaluating low cost alternatives. So far I have not found an alternative with sufficiently lower cost to justify the safety reduction.

    Perhaps I should clarify a distinction here. The hot water options are usually available on a stove, which is insulated from the cabin. Some heat still escapes and heats the cabin, but not nearly as much as if the water coil were in a heater, which is intended to heat the cabin. You can also install a water heater coil in the heater if you want to use both in the winter, but you would only use the stove in the summer.

    The water heater for the Hydronic systems are generally located in the engine room or non-occupied spaces so you can heat water in the summer without heating the interior of the boat.

    Lets also add safety to the list. Portable stoves are acceptable if they are secured and used in the aft cockpit or with good ventilation. They should not be relied on for heat because when you have adequate ventilation you get very little heat. Conversely, if you are getting good heat you don't have enough ventilation.

    Hot Camp Showers http://www.hotcampshowers.com/index.html (this link was not working when I tested it today, but it worked yesterday so it is probably a temporary outage) has a campfire water heater which is just a cooper coil with a long handle that you lay in a camp fire. With a little experimentation, you could probably make a water heater coil for a portable stove. I would rig up a loop of hot water hose connected to a conical coil of copper tubing in an area of the cockpit where the stove could be secured. Make sure that you provide a mixing valve down stream of the heat loop to provide temperature control.

    I think the diesel heater and diesel stove are a better option. I have not found a cost advantage to propane yet, so why compromise safety?

    Why does it have to be petrol?

    To run most electric water heaters would require about a 2.5 KW generator, but since most people don't want to shut everything else off you would probably need about 5 KW. A much more efficient approach is to mount a heat exchanger on the generator exhaust like this http://www.polarpowerinc.com/products/heat_exchanger/heat_exchanger.htm . In general most engines convert 1/3 of the energy released by burning fuel into mechanical energy, 1/6 of the energy goes into the water jacket and 1/2 of the energy goes out the exhaust. Typical air to water heat exchangers are about 67% efficient so you can recover 2/3 of 1/2 or an amount equal to the output of the engine. So with a 2.5 KW generator and an exhaust heat exchanger you can get 2.5 KW of electrical power and 2.5 KW of heat.

    An even more efficient approach would be to put a large alternator and an exhaust heat exchanger on the main engine. :)

    Why didn't this principal apply to diesel and petrol engines?

    Cheers;
    Mike Schooley
     
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  4. Portager
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    Portager Senior Member

    A college of mine once did a demonstration of our system for a military customer. The electrical power on the customers boat was too unreliable to run our system (they had brown-outs when high power loads kicked in which caused our computers to reset). His solution was to go out and purchase a portable generator and strap it on the aft deck. The customer vetoed the gasoline (petrol) generator, but he agreed to a diesel generator. Things were going swimmingly until we cleared the break water. About a 1/4 mile out somebody noticed that the aft deck was on fire. Turned out that the portable generator fuel tank wasn't splash proof. It splashed fuel on the deck and something ignited it. Fortunately the customers boat was aluminum and all the fire did was scorch the paint so we got off the hook. The moral I came away with was if it wasn't designed for marine use be very careful using it in a marine application.



    My research indicated that the Takagi is the best quality propane tankless water heater and the only one recommend for Hydronics. It sells for $1497.00 compared to the Webasto at US $1,750 or a $253 cost difference. The propane system requires a propane sniffer at US ~$225 so the cost difference is US $28. You still need a propane locker and propane tanks. Where is the cost savings?

    I did find the Poloma tankless propane water heater only costs US $340, but I also found references on the live aboard list that indicated that their surveyor flagged it as a safety risk and their insurance company made them remove it.

    Cheers;
    Mike Schooley
     
  5. Willallison
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    Willallison Senior Member

    Mike, I simply use the Webasto as a well known example of the type - the Takagi may indeed be a better unit. But check out the Webasto Thermo 90S - it is a hydronic unit and would fit the bill nicely.

    I use a methylated spirits cooker (and heater) on my boat. I use it precisely because it is safe - any spills, leaks etc that result in fire can simply be extinguished with water - try that with diesel and you'll do nothing but spread it. The by-product of its combustion is water (plus a little CO2), so there is no CO problem.

    Terry Johnson also states that "there is more to keeping a boat warm and dry than just producing heat. Porper air flow through all the spaces of a boat helps distribute heat, remove moisture...."
    I always ensure that I have a little ventilation when I'm cooking or heating for exactly this reason.

    Diesel stoves have a nasty reputation for making your food taste like fuel.....what more reason could you want?

    You need a great deal more than 2.5kW to run a tankless system. The Eemax system I referred to in an earlier post is simply not up to the job - most of the domestic systems I looked at used about 28kW - that's a bloody big generator!
    A 2.5kw generator needs to operate for at least 1/2 and hour in order to heat enough water for 1 five minute shower using an immersion heater. No matter how you do it, it simply isn't an efficient means of getting hot water - better to go the diesel or gas route.
    I only looked at petrol generators because the fuel supply was already on board - plus they tend to be quieter, cheaper to buy and lighter.

    For me, it always has - but designing a boat to accept two different types of cookers is a whole lot different to designing one to accept both shaft drive diesel and outboard propulsion!

    As I said before - we all have our views on the best way to go about getting hot water, heat and food. This should be one area where we can all be accomodated. Rather than arguing about which is the best way, lets come up with a design which will allow us to install the system of our choice.....
     
  6. Portager
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    Portager Senior Member

    ???The Webasto Thermo 90S is an excellent diesel heater. We have both recommended it. The Takagi is an excellent propane heater.

    The risk of diesel spill for permanently plumbed systems is nonexistent, except at the fill spout where there isn't an igntion source. The main issue with methylated spirits cooker is the consumption of oxygen and the production of water. For every pound on fuel burned you produce 7 pounds of water.

    I think you made my point very well. If the combustion is confined, combustion air is drawn from outside and all exhaust products are vent overboard then the interior oxygen is not depleted and the water vapor isn't a problem, therefore ventilation requirements are reduced and the efficiency of the system is greatly improved.

    I think you have confused diesel stove with the old pressurized kerosene stoves. The diesel stoves I am talking about have a sealed combustion chamber and the heat is conducted into the heating plate. Combustion air comes from outside and all exhaust products go outside. These units do not have a reputation for making your food smell like fuel. They do have a reputation for being the safest and most efficient stove available. There is also a lot of erroneous information and misconceptions regarding them. The only valid complaints I know of is they take longer to heat up than a propane stove.

    I was trying to be nice. If the water is heated by waste heat and stored in an insulated container you can accumulate heat over the day and use it as required. 1 hour of generator operation per day (plus some margin for heat loss) would be sufficient for 2 showers. It will take more than an hour per day to recharge the battery bank.

    What about gas and diesel stern drives. A duo-prop stern drive provides 10% to 15% more thrust than a single prop, so a 135 HP to 140 HP duo-prop stern drive equals a 150 HP outboard. The 135 HP gas stern drive is lower cost than a 150 HP outboard and you get heat and electrical power very economically. In addition the buyer/builder has the option of using diesel.

    I am trying very hard to make the selected system work, but I don't think most people fully understand the impact that choosing an outboard has on the rest of the system. I said a long time ago that we need to add the cost of the water heater to the cost of the outboard to compare it to the inboard. Now we know that with either the propane or diesel tankless water heater will cost >$3,000 US. Did we make the right choice?

    Cheers;
    Mike Schooley
     
  7. Willallison
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    Willallison Senior Member

    Ok, if diesel is the best cooker and Webasto / Takagi both make excellent heater / hot water systems, then for those who choose this option, the cost would be similar regardless of engine type. And if you want hot water and space heating on demand (without running an engine) then the options are still the same.
    I, for instance, wouldn't install a Webasto system, because I couldn't justify the cost. I'd have something like a Bosch LPG tankless heater (for about $400) and a small 2-burner stove. I wouldn't install an oven in a boat the size of O-1 and I'd rather use my BBQ out the back anyway. My experience is that the little metho heater I already have (<$100 US) does an excellent job, so I wouldn't bother going to the expense of an all out, plumbed in system. Yes it creates moisture so I need to ventilate more than would otherwise be necessary, but it gives out so much heat that it doesn't matter.

    I'm not saying that this is the best or only option for everyone - quite the opposite in fact - as I said before O-1 should be engineered to accept all the feasable cooking and heating options.

    That's exactly what I said - you'd need to run a generator for at least an hour in order to have two showers. Therefore, regardless of type, a tankless sytem is a more efficient way of doing it. Granted, if you're running a generator (with sufficient capacity) anyway, then you might as well be using it to heat water.
    As far as needing to run for more than an hour a day to maintain battery charge goes, I guess it really depends on how you use your electricity and on your batteries. I have two semi-deep cycle batteries on my boat. Essentially I use one as both the house and starting battery and keep the other as a 'spare'. In five years of cruising I've only once been without battery power (alternator wasn't working correctly). On a daily basis I would average about 30 minutes running, but on occaisions I have remained at anchor for 2 - 3 days (this has necessitated the use of my 'spare' to start the motor so as not to completely destroy the house battery) Without the quite high drain electric fridge that I have on board, I could comfortably go longer.
    I have also found that I need to run for at least 30 minutes in order to heat my water enough for a shower. But of course, it doesn't stay hot for very long, so am restricted to showering just after going somewhere - not always when I want my shower. I've also regularly just gone for a raz for 1/2 an hour in order to heat the water up - and I can tell you, that definitely isn't the most efficient way to heat water!:D

    Choosing outboards does have ramifications as far as hot water goes. You can't simply use excess heat to create stored hot water. But for about the same cost as a decent heat exchange type hot water cylinder, you can have an LPG tankless heater which is able to provide instant hot water on demand. I don't see that as a bad trade-off. And whilst I don't want to re-ignite the debate over propulsion systems, take a look at the Surf Scooter that has been talked about recently http://www.devlinboat.com/dcsurfscoter25.htm
    Where's the cockpit gone - it's full of engine! To avoid this you would need to raise the floor at least 1/2 a meter - suddenly it's a very different boat.
     
  8. Portager
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    Portager Senior Member

    Be very careful with any LPG system. Research it thoroughly and make sure that the manufacturer recommends it for your intended use.

    The Aqua Star models 38B and 125 are made by Bosch.

    "The 38B is not approved for boat or RV installations." http://www.controlledenergy.com/pdf/38bman.pdf

    "This product is not approved for manufactured homes (mobile home), recreational vehicles (RV) or boats." http://www.controlledenergy.com/pdf/125xman.pdf

    The Aqua Star model 240FX is made by Takagi. The FAQ at http://www.houseneeds.com/shop/HeatingProducts/WaterHeating/t-k1/240fxfaq.asp states, "Can tankless water heaters be installed anywhere?
    The Aqua Star 240FX (or any gas tankless water heater) cannot be installed inside of bathrooms or bedrooms or in mobile homes, recreational vehicles or boats. Closets are fine as long as adequate air supply is present."

    Cheers;
    Mike Schooley
     
  9. Willallison
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    Willallison Senior Member

  10. Tim Bard
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    Tim Bard Junior Member

    Hi, I too am looking at diesel for power, cooking, heating nd water heating. Why carry more than one fuel? For power diesel engines and outboards are availble, for cooking, baking and cabin heating look at WALLAS from Finland. For water heating look at EBERSPACHER from Germany. It seems that the cooking heating thing is a "done deal". I am trying to figure out how to adapt the smallest EBER to provide hot water for the galley and shower on demand. I haven't had time to contact EBER on this yet but it seems this can be easily done. The only problem I haven't worked outhe detail on is how to simply store a volume of hot water without a real tank. One concept is to use oversized piping from the heater to the use points and a very small re-circulation pump back to the heater inlet, how best to control this is ???. The main pump from the sweet water tank can be a Flo-jet constant pressure VSD (no tank) pump for hot and cold.

    All of this is for a modern Edwardian Gentlemens Launch for the Bays and Hawkesbury area of OZ.

    Regards,

    Tim
     
  11. Willallison
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    Willallison Senior Member

    Got a pic of the boat Tim?
     
  12. guest

    guest Guest

    propane hot water heaters

    I actually did some serious research into propane hot water heaters some time ago. I had a manufacturer lined up, for prices that would put takagi to shame. I tried to do some market research and found that the market is not ready for this yet. A number of insurance policies will not cover a marine vessel with this type of item. So.. I dropped the idea. But, If anyone is interested in ordering a quantity of these things, post your contact info.
     
  13. Duane Mc
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    Duane Mc Junior Member

    Has anybody ever seen or read about a small electric heating device that attaches to a shower outlet and makes warm shower water?

    I remember seeing one at a small resort washroom during a visit on the island Culebra about a decade ago -- it contained a small electric coil that somehow safely separated the water flow from a 120 volt current and produced very warm water.

    Because there is no hot water holding tank and makes warm water on demand, it seems like such a device would be nice on a boat. Using an inverter to make 120 volts would be necessary though -- I wonder how many watts it draws?

    Duane
     
  14. Willallison
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    Willallison Senior Member

    These devices are readily available - and mention has been made of them before for possible O-1 heaters - the problem is that the amount of energy required to run them would require either a massive (and heavy, expensive) battery bank or a generator. In bigger boats, the latter isn't a problem - then again, neither is space for a hot water cylinder. It also means that you lose any heating capacity that can be gained whilst underway - ie heat from the engine
     

  15. Duane Mc
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    Duane Mc Junior Member

    Thanks Will, I guess that would be a problem as to why these little electric heaters are not so popular on boats -- the power draw would really tax the battery banks.

    However, since they would only operate for -- say, a three to five minute shower, perhaps some kind of capacitor storage device instead of a battery source would work. Capacitors -- unlike batteries, release lots of electrical energy quickly and are light weight devices. Still, there is that problem of making lots of electricity in the first place.

    Duane
     
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