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  #61  
Old 03-11-2010
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Ther are many components to efficiency, but the main two are...

* Exhaust temperature. lower is better.
* Control of excess oxygen, or draft control.

The fuel type is not specifically relevant, but generally proper draft control and low stack temperatures (high efficiency) are simpler to achieve with propane. That said, diesel clearly offers the best combination of simple and compact "BTU storage" in a fuel tank and is more efficient in that sense.

I suggest Googling general furnace efficiency to learn more.
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  #62  
Old 04-05-2010
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Scottyt's right. Though John R Pollard makes some interesting observations, the total amount of heat that comes out of the stove has to equal the heat generated by the burning fuel--no more, no less, counting that which goes up the flue or is otherwise lost to outside.
What heat is radiated after the flame is out is only that which was absorbed by the stove and surrounding objects while the flame was burning. When the stove was first lit, the metal and the boat had to absorb heat before it was hot enough to radiate heat. You might say that's the heat it gives off after the flame goes out.
Baffles, materials etc. make a stove more efficient by controling the air flow to the flame, limiting the flamable gasses that escape without being burned, and limiting the heat that's lost up the flue. They make the stove heat the boat more efficiently, but by themselves don't make it any hotter.
So Medsailor's calculations stand on their own, and don't need to take stove design into account.
John V.
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  #63  
Old 04-05-2010
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Quote:
Originally Posted by JVallely View Post
Scottyt's right. Though John R Pollard makes some interesting observations, the total amount of heat that comes out of the stove has to equal the heat generated by the burning fuel--no more, no less, counting that which goes up the flue or is otherwise lost to outside.
What heat is radiated after the flame is out is only that which was absorbed by the stove and surrounding objects while the flame was burning. When the stove was first lit, the metal and the boat had to absorb heat before it was hot enough to radiate heat. You might say that's the heat it gives off after the flame goes out.
Baffles, materials etc. make a stove more efficient by controling the air flow to the flame, limiting the flamable gasses that escape without being burned, and limiting the heat that's lost up the flue. They make the stove heat the boat more efficiently, but by themselves don't make it any hotter.
So Medsailor's calculations stand on their own, and don't need to take stove design into account.
John V.
You know, I've been meaning to get back to this one. Intuitively, I'm inclined to agree that you (and Scotty) are correct on this.

Yet I do continue to wonder what the advantage to having the appliance is then (other than containing and venting the exhaust). Why not just run the open flame from a burner?

I guess what I mean in part by this is, that when "rating" the output of a heater, does the rating standard or formula only track btu content of the fuel source?

Or, in other words, are we talking about apples and oranges? There is a btu content of the fuel source, and a btu rating of the appliance. But are they necessarily one and the same?

This would seem like a crude way to calculate btu output of an appliance -- seems like any two appliance that consumed the same amount of fuel would always have the same btu rating (the fuel's btu rating). And yet some appliances (heaters for example) are rated more/less efficient than others with identical output.

I still would be interested to hear how the numbers crunch on the diesel version of the Dickinson heaters. This might give us some indication if we're comparing apples to oranges. But I'll let someone else do that.
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  #64  
Old 04-05-2010
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An electric heater is great for use pier side, then a drip type diesel or kerosene heater like a taylor lavac stove. Taylors 079D I use a combination of electric heat and the kerosene heater to keep the cabin toasty warm even down to 20 degrees F.
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Old 04-05-2010
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Those are good questions about measuring the efficiency of the fuel vs that of the appliance, and I don't know the answers, precisely. From my experience heating with wood, I can tell you that the efficiency of a stove refers to its ability to extract the maximum amount of heat from the fuel. It's measured in various ways. But basically, a cord of dry locust will contain x BTU's. Stove A will burn it and produce a percentage of that, while stove B will produce a different percentage.
Much has to do with the amount of the fuel that actually gets burned. Combustion requires fuel, air and heat. Much flamable gas leaves the burn zone without combusting because it never encounters air and heat in sufficient amounts before it gets sucked out of the stove. A more efficient stove puts the right amount of air, heated to the right temperature, in the right place. Likewise, a flue that is too cold won't draw enough air into the burn zone; one that is too hot is burning some of the fuel after it's left the combustion chamber and it goes up the chimney. All stoves aren't equal and internal design matters, but an inefficient stove gets more heat out of a unit of fuel than an open flame does, just by managing the above three requirements better. And by absorbing some of the excess heat to radiate after the fuel burns out.
I don't know how manufacturers tweak their numbers to their advantage, but I'm sure they do and personally I don't take them seriously. Outside temp, flue temp, room air temp, humidity and other factors affect whether my stove burns as efficiently in my boat as it did in the lab that tested it. I wouldn't expect every Newport 9000 to produce 9000 btu's uniformly. I'd just expect it to produce less than a Newport 12000. About the only thing we can predict or control is how well we insulate.
Probably more than you wanted to hear, but it's about all I have to think about during the long northern winter.
John V.
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Old 04-26-2010
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Tiny Tot by FATSCO

You might look in a Tiny Tot by FASTCO ( they have a website) . They are small and efficient and retro sturdy and can burn whatever little bits you can find on the beach including bark. With the stove top attachment you can cook or make coffee. Sailors have used them for years.
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  #67  
Old 05-02-2010
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Informative Thread

Wow - there's a lot of great information in this thread!

I'll chip in with my two cents' worth... My boat came with a force 10 propane (exposed flame) bulkhead heater. It's essentially useless as far as I am concerned, because it simply loads the cabin with moisture, and has obvious carbon monixide risks, while you're at it. When cruising, I might use it on a very cold morning and then vent the cabin while we sail. As an on-again, off-again winter liveaboard in a wet climate, I found that an oil-filled electric heater coupled with a basic fan kept the boat toasty warm, and a dehumidifier running into the bilge kept the cabin bone dry, all at an affordable cost, with very little in the way of up-front cost.

That said, for cruising, I'll replace the force 10 with a dickensen propane bulkhead heater, but only because there's already propane to the heater. If I were starting from scratch, I'd use a diesel heater, partially because they are more efficient, and partly to cycle through the fuel in my tank more often. Even though I spend a lot of days sailing, during the winter my diesel fuel can sit for a long time, and that doesn't do anyone any favors.

So I'll substitute the open flame propane bulkhead heater for a closed flame dickenson for the time being, and then install a hydronic system running on diesel when the money faiery pays me her next visit. I like that you can capture heat from the heat exchanger during the day to keep the boat warm if you are running under power.

Friends who have such a system changed out their Espar diesel furnace for a german variant, which they say cut their annual maintenance costs down from $1-$1.5K per year, to about $1K every 5 years. They heat a 44 foot sailboat, and can achieve positively tropical temperatures when it's below freezing out.

I'd love a wood heater on board if it suited my needs, but the reality is that I simply don't have the space for wood, or the time to muck around with it when I have sailing students aboard.

Any thoughts on the best manufacturer and configuration for a hydronic system would be much appreciated.

Cheers!
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  #68  
Old 05-09-2010
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Diesel....but with a caveat.

Being from Alaska, I have come to often desiring heat, quite often requiring heat, and fairly often needing to jury-rig ways so that I can continue having heat.

I've seen minus 58 degrees in Fairbanks, Alaska, and thus have grown quite fond of localized, indoor heat. I still hate OUTDOOR heat and humidy, but indoor heat that one can shut-off when one desires is quite fine in my book. I think too many nights of non-banking woodstoves at minus fifty degrees turned me into a real-life Sam McGee from Robert Service's "The Cremation of Sam McGee. See link here http://www.arcticwebsite.com/ServiceCremation.html, as least as far a desiring heat.

As far as boat-heat is concerned, I have a "Hi-Seas" diesel bulkead heater that works via a small brass electric fuel-pump and a fancy, mechanical control valve. This system worked great for a number of years, and the quiet, steady tick from the fuel-pump always told me everything was okay with the system. That tick meant blessed heat...and as long as it was ticking, I was warm. Diesel is DEFINITELY the ticket for good, efficient boat heat in a cold environment...but there is a caveat:

Well, sounds can be just as deceiving as looks, and sometimes one can have more heat than one would EVER want..

The first time I woke up and put my feet down on a spreading puddle of diesel fuel on the cabin sole, I knew I should look into the cause.

The first time I woke up to a puddle of spreading, FLAMING diesel fuel on the same cabin sole, I knew I should look into the cause and find a solution RIGHT NOW...I mean, not tomorrow, not next hour...THIS minute. Nothing like flames on a boat to get one into quick action. After using almost 3 fire-extinguishers to put out the flaming puddle and making SURE it was out (a stream of flaming oil kept coming from the heater onto the sole like napalm!!), I began to ascertain the problem and then a possible solution. No damage, thankfully except for days of finding yellow extinguisher dust EVERYWHERE and my ego. I think my ego was even coated with that yellow dust!

The problem #1: The fancy mechanical control valve decided to go haywire internally. Problem #2: The trusty electric fuel pump doesn't know it was an accomplice to a boat that could have burned to the water-line and didn't know when to shut-off.

The solution. The circular file for both of offending parts. Well, I still use the electric fuel pump as a transfer pump and a bleeding pump.

I still needed heat, though. These kinda things usually happen when it's frigid...strange, eh? My solution: I obtained a copper 1 and a half gallon day tank with bicycle valve from an old kerosene stove. I went to the hardware and aqcuired a very simple and cheap needle valve-type shutoff valve that fits 1/4" copper pipe and a new length of pipe. I connected the pipe to the day-tank's output fitting and the connected the needle shutoff valve directly to the input for the heater. The day-tank fits neatly in the head, and after I took off the blue paint and polished the copper, it looks nice to boot. I drilled a small hole for an air hose through the bulkhead, and bungy-corded an old-fashioned style bicycle hand-pump to the main cabin bulkhead, this I attached to the day-tanks air fitting. Am looking for an old brass antique-style bike pump that works. Anybody have one?

The system works wonderfully and extremely simply AND much more safely. Here's how:

When I want heat, I simply pump up the air in the day-tank, pressurizing the fuel/air mixture. This starts the fuel flow. I adjust the needle-valve so it lets in just enough fuel to light the heater, I then pump up the day-tank to full pressure and re-adjust the needle-valve so it works fine for a steady flame. Gradually, as fuel is used, the tank air-pressure drops...and so every once in a while, I need to re-pump the day-tank. It is safer because if I fall asleep or leave the boat, the air pressure drops to the point where it doesn't allow ANY fuel to the heater...thus acting as a good fail-safe to anymore unexpected fires.

With this system, the day-tank fuel lasts about three days worth of heat at a gallon and a half. That's about a buck fifty a day for heating costs at three bucks a gallon. When using the original electric fuel-pump format, I used up quite a bit more heater diesel fuel and plus had the disadvantage of a burning boat.

This system keeps the boat at a toasty 68 to 80 degrees (except for the lower ankle sections of the cabin...but a flame-thrower doesn't keep these areas warm on ANY boat!), and does so with grace and simplicity and safety. And becasue I grew up as a woodstover, I love the self-reliance of knowing that I can have blessed heat even without relying on a bit of 'lectricity!! I don't mind a little pumping....it keeps the blood flowing! Keep it simple.

I'll post some pictures when I get them uploaded from my camera.
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  #69  
Old 05-10-2010
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Great story, thanks. You can probably find the brass pump on ebay (like everything else).
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Old 06-12-2010
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Have you considered kerosene? (As used in cabin kerosene lamps.) Much less smelly than diesel. With non-smoke versions it's pretty human-friendly. I used to have a kerosene burner in a central heating system with radiators under the bunks. Excellent combination, kerosene and sailing boats.

The "Ge-HŚ" heater is made in Sweden, by POD AB, thus not available in the US. The only noise is from the circulation pump for the water. Since it is a 12 V pump run on 6 V you have to put your ear next to it to hear it. It has 1.3 kW effect, and requires four 1-m radiators. With that onboard I could sail in the winter, no problem. I put it in the closet, doesn't need much space.

Here is a photo of the burner: POD

Last edited by ulferlingsson; 06-12-2010 at 04:47 PM. Reason: Added product details
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