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Old 25-04-2013, 06:56   #16
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Re: A Cautionary Tale

Another problem, apart from the weight, about fitting a larger calorifier/water heater, is the power needed to warm 20 or 30 gallons. When at sea or anchor this would be from the generator, or the engine. Either way, it would take a long time from cold to warm all the water to fill the tub, and if we only wanted it intermittently for washing, etc., then we would still have to warm it all, which is a waste of power to have it lying idle.
This is why an instantaneous supply, tankless heater sounds so sensible. Power is only used when on demand, and we have two large propane cylinders in boxes on deck, with contents gauges, so we wouldn’t be using any diesel.
I’d like to know why are they considered dangerous when heeled?
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Old 25-04-2013, 10:11   #17
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Re: A Cautionary Tale

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I’d like to know why are they considered dangerous when heeled?
Try taking a camping stove meant for gas vapour (i.e. camping stoves which doesn't make use of an inverted canister) and tilt it back and forth. That should give you a starting point. Please do it outdoors and with safety goggles and gloves etc.

There are two results: It will flame horrendously, and it will most likely sputter and choke in the end, and gas will stream out of it.
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Old 25-04-2013, 10:17   #18
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Re: A Cautionary Tale

I've had two tankless propane units on boats. No issues with either and they worked great. Assuming you pay attention to safety when you install it, no reason it shouldnt be as safe as a propane cookstove... probably safer if used the same way and the new water heaters have all kinds of safety controls in them.. for instance, a propane cook stove will continue to put out gas if blown out by wind from a nearby port or hatch. (or at least the one ihad would) The modern water heater shuts off flow.
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Old 25-04-2013, 10:32   #19
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I've had two tankless propane units on boats. No issues with either and they worked great. Assuming you pay attention to safety when you install it, no reason it shouldnt be as safe as a propane cookstove... probably safer if used the same way and the new water heaters have all kinds of safety controls in them.. for instance, a propane cook stove will continue to put out gas if blown out by wind from a nearby port or hatch. (or at least the one ihad would) The modern water heater shuts off flow.
This echo's my experience and thoughts. Every system on your boat is dangerous, the idea that you could eliminate risk on a boat is silly. You adhere to good practice and...omg... common sense, and these dangers are mitigated to an acceptable level.

I have a gasoline engine... With common sense it has as close to zero risk as one can get. Is gasoline dangerous? Yes. Is my boat in danger because I use it? No. Same with an LPG demand water heater. Just don't be stupid.
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Old 25-04-2013, 17:33   #20
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Re: A Cautionary Tale

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Originally Posted by Caracal View Post
Try taking a camping stove meant for gas vapour (i.e. camping stoves which doesn't make use of an inverted canister) and tilt it back and forth. That should give you a starting point. Please do it outdoors and with safety goggles and gloves etc.

There are two results: It will flame horrendously, and it will most likely sputter and choke in the end, and gas will stream out of it.
Caracal, I don't understand how this demo relates to the use of a LPG flash heater on board a yacht. The heater is fed from the same LPG tank that your stove is, and the stove works just fine when heeled. Liquid/vapour separation occurs in the tank, not in the burner.

Cheers,

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Old 25-04-2013, 17:42   #21
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Re: A Cautionary Tale

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Banned by the government ?? Are they illegal to have on board? Hot foods a necessity but not hot showers? Interesting.....
yes banned unless room sealed. you have to heat your water by another means
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Old 25-04-2013, 18:09   #22
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Re: A Cautionary Tale

As I understand it, the main reason small camping-gaz cookers flare up when tilted is that they don't have a regulator, which impedes liquefied gas from getting as far as the burner jet.
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Old 25-04-2013, 18:16   #23
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Re: A Cautionary Tale

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Caracal, I don't understand how this demo relates to the use of a LPG flash heater on board a yacht. The heater is fed from the same LPG tank that your stove is, and the stove works just fine when heeled. Liquid/vapour separation occurs in the tank, not in the burner.

Cheers,

Jim
Well, your gas stove is propably gimballed and most likely made to take both vapourised and liquid gas. I'm not saying an "instant" heater for sure doesn't have that capability, but I very much doubt it.
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Old 25-04-2013, 19:08   #24
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Re: A Cautionary Tale

tankless or instantaneous water heaters are illegal in Australia in boats or caravans and if the boat is sold must be inspected by a registered gas fitter ,so if it has been done by an owner short cuts are usually taken, the reason this is so is because tankless must have a balanced flue so no products of combustion can enter the living spaces, stoves on the other hand are legal because of the small amount of lpg required ,but even then must have a sniffer installed ,I personally have installed the webasto unit which runs off diesel and 12v a much safer alternative and most boats have both joe the gas man
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Old 25-04-2013, 19:27   #25
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As I understand it, the main reason small camping-gaz cookers flare up when tilted is that they don't have a regulator, which impedes liquefied gas from getting as far as the burner jet.
"Camp stoves" which run on liquid fuel (as most do) produce vapor from the liquid fuel in the vaporization tube which is part of the burner assembly. Liquid fuel flows from tank to the hot vaporization tube where the heat converts it to gas. If the tube is not hot enough or more fuel flows than it can handle (like by elevating or overpressurizing the tank) then it will flare.

Propane by contrast seperates into liquid and gas (vapor) inside the tank. Only gas vapor flows thru the hose to the appliance. The regulator near the tank only controls pressure of this gas. Thus no flare under any kind of normal circumstances....unless maybe you are trying to cook on an inverted cat...

Kerosene or pressurized alcohol stoves found on boats work on the same principle as camp stoves.
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Old 25-04-2013, 19:43   #26
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Re: A Cautionary Tale

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Well, your gas stove is propably gimballed and most likely made to take both vapourised and liquid gas. I'm not saying an "instant" heater for sure doesn't have that capability, but I very much doubt it.
Yes, the stove is gimballed, but no, it is not "made to take both vapourised and liquid gas". As others have tried to point out, the phase separation from liquid to gas occurs within the storage tank, not in the stove or heater.

Nothing so far posted has shown that the flash heater when installed and operated correctly is hazardous.

Cheers,

Jim
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Old 25-04-2013, 19:53   #27
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Re: A Cautionary Tale

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Nothing so far posted has shown that the flash heater when installed and operated correctly is hazardous.
Fair enough. Do what you must.
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