Tankless water heaters

[wingssail]

Originally Posted by AndyEss

...I don’t go below and shower if it’s blowing, and I don’t use hot water often for washing dishes...

One of our mottos on board Wings is that we arrive clean, well rested, and first.

The clean part usually means a shower (a hot shower) in the last hour or so before arrival at a port after a long crossing. If the crossing is rough that means we're showering in rough conditions.

Being at sea on a boat does not mean camping out or giving up the conveniences of home (in our case, the boat).

It has not been a problem.

[wingssail]

Originally Posted by Dockhead

It cost $145??! As the trollface meme says, lolololololol.

Your boat, your rules, your budget, your economy, but:

Propane is not "far safer than alcohol, diesel and CNG". This is just factually totally incorrect. The problem with propane on a boat is that its being much heavier than air, it settles in the bilge, forming what is in essence a fuel-air bomb (see: https://en.wikipedia.org/wiki/Thermobaric_weapon). CNG is lighter than air and floats harmlessly away. Alcohol is not too good from a fire point of view, but at least cannot form an explosive mixture. Diesel is extremely safe. If you even intended to start a fire with diesel fuel, you would find it a challenge to ignite. Propane is a very good weapon, of extreme destructive ability in an environment where it cannot drain away and dissipate, like in a house. 100 grams of propane, mixed with air, has the explosive power of 195 grams of TNT.

Here's just one example of what can happen: https://assets.publishing.service.go..._trenchard.pdf

You trust a $145 Mexican device to keep you separated from that kind of explosion? Is money really that tight?

Did you miss the point that we chose it for convenience and safety, not price. And hey, is it really necessary to point out that it is a "Mexican device"? Do you have prejudice against Mexican devices? I judge the quality not the race of the maker.

Your boat your rules, but if we are ever in the same anchorage, we'll have the sundowners on my boat, not yours.

That is what you came up with? One instance in 20 years? And it seems to me that the propane locker was not properly sealed and allowed gas to run down to the gen-set space. Is that allowed in UK? Ours need to be vented overboard.

Alcohol stoves cause burns and fires due to their invisible flame.

Diesel needs to be started by something, usually alcohol, and the fumes are toxic, plus if the flame goes out (gets blown out) the diesel stoves I've used do not have flame detectors which can cut off the flow of fuel. (Correct me if I am wrong about this.) In 1980, or thereabouts, a diesel fire on a US Army Reserve Tugboat off Point Robinson in Puget Sound burned and killed four crew members. I was on the scene and we were pulling people out of the water after they jumped in. It was terrible, the burns, and the fire could not be put out. The boat, around 100ft, burned and sank. Diesel.
CNG is lighter than air and rises. Good. It is useless most places in the world
and not too safe if you are in Papua New Guinea trying to modify your CNG system to use some other fuel.
Propane has a very effective leak detection system: our noses. Anywhere in the boat we can smell the slightest propane leak. We can even tell when it is getting low because the smell changes. It would not occur the way the report you provided states because the gas valve would be off at night and the gas, if leaking, would vent overboard. The safety of propane is also due to the common availability of parts needed to maintain it and keep it is good repair.

I'm not trying to change you views, I know that is not possible. But maybe you can cool down the rhetoric. Other peoples views have some validity too.

[boatpoker]

Originally Posted by AndyEss

I don’t understand what the size of a boat has to do with carbon monoxide production.

The size of the boat has to do with the ability to draw combustion air and expell exhaust air from the unit. Opening ports, hatches the exhaust and intakes must all be minimum distances from each other. These minimum distances and the extra ducting involved make it almost impossible for vessels of the size most common on this forum.

Also the unit itself must be designed to accomodate intake air from outside the vessel to sealed combustion and exhaust to outside the vessel.

This only applies if interested in meeting ABYC Standards or following manufacturers instructions. If this is not a concern to you, I will not argue

[wingssail]

Originally Posted by Pete7

Hmm, not this side of the pond and all come with instructions not to fit in boats, presumably for a good reason. Shame because I did look and decided not to.
Pete

They told us the same thing in 1986. The dealer put on the receipt, "Not for use in a boat" however he was only a boat equipment dealer. However he could not say what exactly were the reasons. Nothing was said about distances apart of intake and exhaust vents or any other reason.

F**k it I said, and I installed it.

Worked good for about 10 years, then got rusty. The next one was stainless steel, looked nice, worked better.

So, like boat poker says, if you are a slave to regulations done by some guy in an office, who's thinking about 200lt/min of water heated, in a ferry boat, with paying passengers, then, don't do it. Our little toys, however, are designed with safety in mind for a small installation as needed for the use we put them to.

[AndyEss]

Originally Posted by Pete7

Hmm, not this side of the pond and all come with instructions not to fit in boats, presumably for a good reason. Shame because I did look and decided not to.

Pete

Well on our side of the pond, propane use is allowed on boats. It works quite well (with proper safety considerations), relatively inexpensive, reliable, and does not give off carcinogenic exhaust fumes as given off in large concentrations by low temperature/low pressure burning of diesel fuel

[AndyEss]

Originally Posted by boatpoker

The size of the boat has to do with the ability to draw combustion air and expell exhaust air from the unit. Opening ports, hatches the exhaust and intakes must all be minimum distances from each other. These minimum distances and the extra ducting involved make it almost impossible for vessels of the size most common on this forum.

Also the unit itself must be designed to accomodate intake air from outside the vessel to sealed combustion and exhaust to outside the vessel.

This only applies if interested in meeting ABYC Standards or following manufacturers instructions. If this is not a concern to you, I will not argue

It’s a low Btu water heater for Claude’s sake, not a coal fired power plant. I know my home propane tankless water heater has forced air because it is a condensing unit, and it is about 5 times larger than my boat heater, but convection easily takes care of venting the exhaust. Propane burns very cleanly because it is a short chain hydrocarbon.
Further, I don’t see anywhere of the same concern of the horrific, nuclear winter type concerns for propane cook stoves.
As Mainesail pointed out, propane cook stoves are allowed with no outside venting or outside combustion air because they are supposedly “under observation” or somesuch during use.
The thing about the propane water heater is all the safety sensors don’t get tired, they don’t get seasick, and they don’t walk away from the heater and get distracted by other activities. All of which human operators of cook stoves might be prone to do.
I consider the water heater to be far safer in design and operation than my propane cook stove. There is no open flame to set things on fire as there might be around a cook stove, or within frying pans on the burners.

[john61ct]

Once an owner has been informed of the fact that propane on a boat is dangerous

then of course s/he is free to do as they like.

We all have different levels of risk tolerance, and ability to follow clearly spelled out safety test / checklisted protocols for reducing the risks involved.

I'm not stating my own preference on the matter, just pointing out "to each their own" applies once we've helped inform each other.

Getting into a petrol-fueled vehicle traveling fast on our highways is likely riskier than anything else we do, except say SCUBA, rock climbing, looking for a nice wife in beer bars. . .

Single-handing long bluewater passages without AIS, radar etc is also considered "reckless" by many.

[Chotu]

I have to put in my experience. Add some fuel (diesel? Propane?) to the fire.

Propane systems can be absolutely safe. They just need to be looked at after every decade or two. I have had propane in RVs and in boats for decades. I build my own too. From standard off the shelf parts at the hardware store. Copper refrigerator tubing and flare fittings. That's it.

I have a proper propane locker that drains overboard and run a single line with no splices from the manifold in that locker to the propane powered device. That means there is one, single point of possible leak per device and that is at the connection to the device itself.

I have made some propane systems on RVs at first and saw the leftovers of one in a British boat I used to own. They even had a propane refrigeratior in that one.

I built a boat without thru hulls below the waterline. None. Propane (and gasoline..oh my!) has a slightly elevated risk as compared to diesel. No doubt. However, seacock failure is about the same risk level. I traded one risk for another and designed safety into my systems.

I have propane refrigeration, a propane cooktop, a propane cabin heater and was installing a propane on demand hot water heater (inboard gasoline tanks too!!!). I figured might as well stick with one fuel.

I noticed the old British boat had a propane refrigerator so I tried it out. It's actually a 3 way propane/DC/AC refrigerator. No digging in a pit for my food. Just like in a house. Swing open the door and get whatever. Keeps ice cream hard too.

It all works just fine. As do inboard gasoline tanks that are not in an engine room and don't leak. My boat has outboards.

The key to safety with propane is the propane locker and manifold along with running a single uninterrupted line to each device. You can't cobble together splices and Y connections around the boat. ABYC specifies a single uninterrupted line.

Surely a robust set of solar panels, induction cooktop, DC refrigeration and a DC powered hot water heater are the best way to go. Or so you'd think, but then again, the majority of fires on boats are electrical in nature. DC still seems nice though. You don't need to worry about running out of sun. Or refilling the sun.

But basically it's "pick your poison" as none of these systems are without risk.

Propane is also infinitely more reliable than other sources. Clean burning so no soot buildup like diesel, can't break or corrode like electrical components, no generator to maintain, it literally can't fail. It's a hollow tube with no moving parts. There is certainly something to be said about that.

The reason I tried propane was the fact that it's in RVs without failure. And an RV is a MUCH more unforgiving place than a sailboat for lines and connectors. It's violently banging around continuously over the bumps of roads. A boat is gently moving in comparison.

I'm here to report that no, proper propane installations don't leak. Yes, I'm still alive. Even with a proper gasoline tank installation. And yes, they can be done with absolute safety.

I'm also here to report that it's not terribly convenient to have to fill the tanks every couple months. I carry 80lbs (4 standard BBQ tanks) which lasts a couple months. And yes, they do add some weight as diesel or other petroleum based energy sources do as well, but that the electrical savings using propane requires a smaller battery bank, less wiring, etc so it's actually lighter.

On the carbon monoxide side of things, I'm paranoid. Everything is direct vent. I don't mess around with carbon monoxide. The British boat I once had had an unvented propane hot water heater in the head. We started using it and were shocked to find lethal levels of carbon monoxide accumulate in minutes in the head. I'm so paranoid I use the co alarms with the ppm readouts. Your exposure is short, but at the same time, it's very high. Don't locate an unvented propane appliance in a small space. It's like what boatpoker said. You may not die or even get sick but it is poison and is not healthy to breathe often.

[GordMay]

Originally Posted by boatpoker

The size of the boat has to do with the ability to draw combustion air and expell exhaust air from the unit. Opening ports, hatches the exhaust and intakes must all be minimum distances from each other. These minimum distances and the extra ducting involved make it almost impossible for vessels of the size most common on this forum ...

I believe that the referenced minimum separation distances refer to VENTILATION intakes, and exhaust vents, not combustion-air intakes.
ie: Ventilation system intakes must be sufficiently separated away from potential contaminant sources.
Ventilation intake must draw through an intake grille or register located on an outside wall or soffit and not the roof.
Ventilation intakes must be located at least "10" (varies by jurisdiction) feet from any appliance (exhaust) vent, or any vent opening from a plumbing drainage system.
As boatpoker noted, you can't place an exhaust vent "near" an opening (doorway/hatch).

[Dockhead]

Originally Posted by wingssail

That is what you came up with? One instance in 20 years? And it seems to me that the propane locker was not properly sealed and allowed gas to run down to the gen-set space. Is that allowed in UK? Ours need to be vented overboard.

I mentioned the Lord Trenchard case only because it was the subject of a full MAIB accident report, which has a lot of important detail in it, relevant to this discussion. There are previous threads on CF with references to dozens of accidents, if you care to do a search. As I said, someone gets blown up almost every year.


The Lord Trenchard case is particularly interesting and particularly relevant because the boat was a Royal Navy training vessel which was exceedingly well run, much better than any cruising boat I know, with great care taken with gas safety, much more care than taken on any cruising boat I know. This degree of care went so far as to require the crew to pump out the bilges every morning -- pump out gases using the diaphragm hand bilge pump.


Despite all this care, they blew themselves up, and one cadet lost a leg, and the boat was blown to smithereens. The gas locker on Lord Trenchard of course drained overboard. The problem happened because of a tiny flaw in the sealing where the gas pipe left the locker, and that was enough to allow a fatal quantity of leaked gas into the hull volume. Remember, propane has twice the explosive power by weight of TNT. It only takes a little bit.


Moral of the story -- gas on board is bloody dangerous and is not "absolutely safe" even if you are really careful. "Reasonably safe" -- perhaps. But how reasonably safe is a boat where safety rules are flaunted and derided as something produced by gnomes in offices?

Originally Posted by wingssail

. . . Propane has a very effective leak detection system: our noses. Anywhere in the boat we can smell the slightest propane leak. We can even tell when it is getting low because the smell changes.

Wait a minutes, you detect leaks by smell? If you ever smell propane on your boat, it's too late, you're already sitting in a bomb.


And what are you smelling when you are "telling it is getting low" -- combustion products? You don't even vent it? Have you ever heard of carbon monoxide?

Originally Posted by wingssail

It would not occur the way the report you provided states because the gas valve would be off at night and the gas, if leaking, would vent overboard. . . .

That is precisely what the Lord Trenchard crew thought! That's exactly why I posted that report.




Be safe, man. A really good start to being safe with gas on board is scrupulously following the ABYC rules, which are very sensible and very effective.

[daletournier]

Originally Posted by Dockhead

I mentioned the Lord Trenchard case only because it was the subject of a full MAIB accident report, which has a lot of important detail in it, relevant to this discussion. There are previous threads on CF with references to dozens of accidents, if you care to do a search. As I said, someone gets blown up almost every year.


The Lord Trenchard case is particularly interesting and particularly relevant because the boat was a Royal Navy training vessel which was exceedingly well run, much better than any cruising boat I know, with great care taken with gas safety, much more care than taken on any cruising boat I know. This degree of care went so far as to require the crew to pump out the bilges every morning -- pump out gases using the diaphragm hand bilge pump.


Despite all this care, they blew themselves up, and one cadet lost a leg, and the boat was blown to smithereens. The gas locker on Lord Trenchard of course drained overboard. The problem happened because of a tiny flaw in the sealing where the gas pipe left the locker, and that was enough to allow a fatal quantity of leaked gas into the hull volume. Remember, propane has twice the explosive power by weight of TNT. It only takes a little bit.


Moral of the story -- gas on board is bloody dangerous and is not "absolutely safe" even if you are really careful. "Reasonably safe" -- perhaps. But how reasonably safe is a boat where safety rules are flaunted and derided as something produced by gnomes in offices?





Wait a minutes, you detect leaks by smell? If you ever smell propane on your boat, it's too late, you're already sitting in a bomb.


And what are you smelling when you are "telling it is getting low" -- combustion products? You don't even vent it? Have you ever heard of carbon monoxide?







That is precisely what the Lord Trenchard crew thought! That's exactly why I posted that report.




Be safe, man. A really good start to being safe with gas on board is scrupulously following the ABYC rules, which are very sensible and very effective.

Dh, most of us carry Lpg, that's just a fact. Many sailors live safe fulltime cruising lives heating their water with instant gas heaters, wingsail and the Cates for example, they arent idiots , common sense is the main ingredient nessacary to travel around the world on a cruising sailboat, if you fint have it you'll find a way to kill yourself, gas or no gas.

I've often had to jury rig systems to fill my bottles in foreign countries and I'm sure I've broken ABC rules etc, but I get the job done without dieing.

[Connemara]

Dunno if this applies to onboard systems, but.... We have a tankless water heater in the house, which we like a great deal; the drawback is that you have to run it a while before you get hot water. On board, that would mean going through a lot of fresh water, unless the marine versions are built with some sort of recycling system.

Connemara

[AndyEss]

Originally Posted by Dockhead

This degree of care went so far as to require the crew to pump out the bilges every morning -- pump out gases using the diaphragm hand bilge pump..

I have never heard of any application of a diaphragm pump to move compressible gases. Diaphragm pumps are used to pump incompressible liquids. The incompressibility of the fluid being pumped is what closes the one way intake and exhaust valves of the diaphragm chamber.
Explosion proof blowers are used to remove gases.
No wonder these supposedly ultra safe naval personnel blew themselves up - they were never pumping any gases out of the bilges if in fact they used a diaphragm pump.
Decades ago when I had a gasoline propulsion engine on my first boat, the engine compartment needed to be vented using an explosion proof blower before starting. It was also recommended to vent the compartment after fueling

[wtmf]

I have a stainless tank shaped like a donut and use a 100 watt light bulb to heat the water. Depending on the outside temp it can get very hot in 6 hours but if it is cold at night it will take all day to warm up to comfortable.

[Dockhead]

Originally Posted by daletournier

Dh, most of us carry Lpg, that's just a fact. Many sailors live safe fulltime cruising lives heating their water with instant gas heaters, wingsail and the Cates for example, they arent idiots , common sense is the main ingredient nessacary to travel around the world on a cruising sailboat, if you fint have it you'll find a way to kill yourself, gas or no gas.

I've often had to jury rig systems to fill my bottles in foreign countries and I'm sure I've broken ABC rules etc, but I get the job done without dieing.

I never called anyone an idiot. I have greatest respect for Wingsail and Cates, of course.


But I consider flaunting the rules, violating the manufacturer's own instructions, and apparently not even venting the device, to be extremely bad practice, and I won't mince any words about that, lest doing so might mislead someone else reading this. It's bad practice even if it's done by smart people like Wingsail and Cates. That's my opinion and everyone is entitled to his own, different one; mine is just one voice. But I hope I have argued it persuasively enough that it might help save just one person reading this from tragedy, or even if it just raises a question in someone's mind and stimulates further thought.



"Common sense" sometimes refers to practical wisdom which transcends certain unimportant details, but sometimes "common sense" refers to wilful ignorance of the complexities or full implications of a certain thing. It's a double-edged sword. Don't call lack of proper respect for the dangers of gas on board "common sense".



Like you I've lived with propane on boats my whole life, and I've also done illegal pours from one bottle to another. I'm not entirely proud of the second thing, but done on dry land where spilled gas flows harmlessly away, and with care against overfilling, this is not so horribly dangerous as is spilling gas in a boat with closed bilges.