Tankless water heaters

[Chotu]

Originally Posted by wingssail

The biggest problem is that the water temp for dishes is too hot for the shower.

So I take it you are going straight to the shower head with the hot water from the tankless propane heater? You are not using cold water to mix with it?

[S/V Adeline]

Originally Posted by Lepke

All the AC tankless heaters I have seen are 240v and draw 30 amps or more. Many dive and fishing boats have an on deck shower powered by propane. And electric tankless doesn't heat as high as a conventional water heater. Usually to about 110°F.

The only one I have had experience with is Titan out of Florida, but they offer 110v, draws under 30 amps and fully adjustable (will scald your skin off). We used it for two years.

[mvweebles]

I realize OP asked about electric heaters, there are propane heaters made for RV use such as this Excel model that happens to be vent-free. Fairly decent reviews.

[Maine Sail]

For anyone considering LPG on-demand water heaters just be aware that insurance surveys, if you have a sharp surveyor, will not be in compliance for (US & Canada). We have had to remove a few on-demand propane water heaters due to surveys.

The only way they will be is if they are "room sealed" combustion. This means they need to exhaust to the exterior and take combustion air also from the exterior of the vessel. The only one I know of currently, that can meet the marine standards for on-demand LPG, is the Precision Temp Showermate M-550 EC which can be set up for room sealed combustion.

[mvweebles]

Originally Posted by Maine Sail

The only way they will be is if they are "room sealed" combustion. This means they need to exhaust to the exterior and take combustion air also from the exterior of the vessel.

I don't have a dog in this fight - I'm perfectly happy with my traditional 6-gal electric/engine heat tank, and I question the practicality of using propane for heating purposes (water or ambient), that's a personal decision. Curious how a [ventless] propane stove is considered safe but a [ventless] propane water heater is not?

[Maine Sail]

Originally Posted by mvweebles

I don't have a dog in this fight - I'm perfectly happy with my traditional 6-gal electric/engine heat tank, and I question the practicality of using propane for heating purposes (water or ambient), that's a personal decision. Curious how a [ventless] propane stove is considered safe but a [ventless] propane water heater is not?

A propane stove is considered an attended appliance where a water heater, under the standards, is considered an unattended appliance. Two different classifications of appliance types.

[kenbo]

Originally Posted by Maine Sail

A propane stove is considered an attended appliance where a water heater, under the standards, is considered an unattended appliance. Two different classifications of appliance types.

That's funny, let me introduce you to my wife!

[AndyEss]

Interesting discussion here. Mainesail - thank you for your knowledgeable input.
A lot of this discussion is predicated on how we use our boats. I live on the hook and spend as little time in a marina as possible, so don’t have access to shore power. I do have an electric/engine coolant heat exchanger water heater. The little time I motor, it does a great job of heating water.
I don’t have an onboard generator and don’t want one - just another piece of machinery I would have to maintain and have disturb my peace and quiet, much less my neighbors. My electrical needs are satisfied with 450W of solar panels (about the maximum my boat will easily support) and a wind generator.
My propane tankless heater is mounted in my forepeak right in the shower/head compartment (no V-berth in a HC38) directly under the foredeck hatch. I replaced the dead Wolter heater that the PO had mounted in the same spot with a decent quality residential heater. My experience with heaters intended for RVs has been bad, where residential heaters have been excellent except for rust issues. The heater is direct vented with no bends in the exhaust. Manuals for the heaters allow even 90 degree bends in exhaust lines, subject to some geometrical restrictions, but I had no need to go anywhere except vertically to the deck vent. I personally would be leery of a heater that didn’t vent exhaust, but have no direct experience.
The requirement for outside combustion air makes some sense, as boats can be exceptionally well sealed as compared to a house. Very few houses sink due to leaky construction. As mvweebles notes, stoves don’t need a source of outside air. I personally would think that oven baking would be worse than my own use of the propane water heater as my heater is right next to me while I shower. The rare times I bake, I have been known to wander off and do other things than stare at the oven. Same topic - do the Esper or Webasto diesel boat heaters include requirements for outside combustion air?
Propane for heating water over electric is analogous in many ways to discussions of diesel versus electric propulsion. Propane, though not as energy dense as diesel, is far more energy dense than the best battery. My boat is set up with an ondeck propane storage box that holds 3x10lb propane tanks. One tank lasts me over a month, but I am pretty frugal in my shower times. The problem with sailing with eye candy is that they notoriously are not - which for short trips is no issue.

[boatpoker]

Originally Posted by AndyEss

So you have zero personal experience with using tankless propane water heaters on boats.
Got it.

I have such experience. Several manufacturers specifically mention in instructions not to install in a boat or other enclosed space. It is near impossible to install these things in a boat of our size range as specified by the manufacturer (these specifications have reasons). Not one of these things that I've seen meets ABYC Standards* so be aware that Your surveyor will likely call it out in your next survey and your underwriter may require it's removal.

*I have not seen the one Mainesail mentions

[Dockhead]

Originally Posted by boatpoker

I have such experience. Several manufacturers specifically mention in instructions not to install in a boat or other enclosed space. It is near impossible to install these things in a boat of our size range as specified by the manufacturer (these specifications have reasons). Not one of these things meets ABYC Standards so be aware that Your surveyor will likely call it out in your next survey and your underwriter may require it's removal.

Indeed. And God forbid it blows up and kills someone.



I would never have such a contraption on any boat of mine. Propane is really dangerous on boats; someone gets blown up almost every year in the UK. Saying I've used one for 10 years and not blown up yet; ergo it's safe, is like saying I've been driving drunk for 10 years and no crash yet; ergo it's safe.



And don't even start to compare a $200 Chinese contraption designed for a house, to a $2000 marine stove made of quality stainless and designed for the marine environment. Although the stove is pretty dangerous itself.

Cost of production, probably $7, doubtful metal, no corrosion protection, doubtful quality control, full of explosive gas, in a vibrating, moving, salt air marine environment it was never designed for. What could possibly go wrong?


In my opinion, this is the most foolish place to save money you could possibly come up with. Like buying seacocks made from pot metal to save a little money on bronze.


Do yourself a favor and find one of the 100 other ways of making hot water on board, every one of which is at least an order of magnitude safer than this nonsense.


One dead simple way to do this is to buy the smallest Planar or Eberspacher hydronic heater and plumb it into your calorifier (or add a calorifier). Add a radiator or fan coil and you get cabin heat too. Fueled from your main tank so no extra humping of propane. Dead safe. Should cost you less than a grand all in if you do the work yourself.

[wingssail]

Originally Posted by Maine Sail

A propane stove is considered an attended appliance where a water heater, under the standards, is considered an unattended appliance. Two different classifications of appliance types.

Originally Posted by boatpoker

I have such experience. Several manufacturers specifically mention in instructions not to install in a boat or other enclosed space. It is near impossible to install these things in a boat of our size range as specified by the manufacturer (these specifications have reasons). Not one of these things that I've seen meets ABYC Standards* so be aware that Your surveyor will likely call it out in your next survey and your underwriter may require it's removal.

*I have not seen the one Mainesail mentions

This is another case where a rule is blindly followed regardless of whether or not it makes sense.

A propane water heater is no less "an attended appliance" than a stove. In fact it is probably more attended since it only runs when someone has turned on a tap. People don't leave a tap running and walk away. Stoves on the other hand are often left running (thanksgiving turkey dinner anyone?)

Both have safety features. In fact the propane water heaters I see available now days have far more safety features than stoves.

But rules become dogma, logic doesn't enter into the calculation, surveyors follow rules, and often prostrate themselves before them.

Our propane water heater exhausts in the head compartment about 24" from a small hatch, which is open. It uses interior air for combustion, same as the stove. It is safe, yet some surveyors will happily write it up.

But not all. We have had three surveys in 34 years. The propane water heater was always there. It was never listed as an exception or even noted.

(standby, the surveyors here will respond that those were poor surveyors)

[AndyEss]

Originally Posted by boatpoker

I have such experience. Several manufacturers specifically mention in instructions not to install in a boat or other enclosed space. It is near impossible to install these things in a boat of our size range as specified by the manufacturer (these specifications have reasons). Not one of these things that I've seen meets ABYC Standards* so be aware that Your surveyor will likely call it out in your next survey and your underwriter may require it's removal.

*I have not seen the one Mainesail mentions

I don’t understand what the size of a boat has to do with carbon monoxide production. As far as I can tell, Mainesail’s discussion is the most useful here, and he mentions an approved unit that has the only difference of being capable of an exterior combustion air supply. This has nothing to do with boat size.
As for Dockhead’s disdain for propane on a boat, it is allowed by certification organizations. As for the merits or lack there of in Chinese manufacturing, get rid of your cell phones, electronic navigation aids, radios, laptops, tvs, etc as most of them are manufactured in China, or have appreciable Chinese content. British manufacturing (think Jaguar) quality has had little influence on world trade in many decades.
Diesel exhaust is a known carcinogen. Burning diesel at low temperatures (not in a high compression diesel engine) gives off far more exhaust (inefficient combustion) and larger quantities of particulate matter. Cooking on diesel stoves has become rather rare because of the smell and off flavors such cooking devices introduce. I suspect there are significant health issues that might be associated with such stoves.
Propane does have its problems, granted. Diesel burners introduce other problems not associated with propane.

[wingssail]

Dockhead, You are certainly entitled to your prejudice but I disagree with it.

Originally Posted by Dockhead

Indeed. And God forbid it blows up and kills someone.

I would never have such a contraption on any boat of mine. Propane is really dangerous on boats; someone gets blown up almost every year in the UK. Saying I've used one for 10 years and not blown up yet; ergo it's safe, is like saying I've been driving drunk for 10 years and no crash yet; ergo it's safe.

The danger you refer to is over stated. Virtually all the boats I see out cruising have propane stoves, BBQ and in some cases water heaters. I have heard, in my life, of one propane explosion on a boat, which blew the deck off of a 45'Beneteau, the occupant was not killed and hardly injured, and the boat did not burn, and was sold for salvage, and subsequently used for several years by an IBM software engineer I knew well. if someone gets blown up on a boat almost every year in the UK I'd like to see some accounts of this, You should be able to show me 10 or so from the last decade. Perhaps there is some other safety issue in the UK that isn't present elsewhere.

And don't even start to compare a $200 Chinese contraption designed for a house, to a $2000 marine stove made of quality stainless and designed for the marine environment. Although the stove is pretty dangerous itself.

Cost of production, probably $7, doubtful metal, no corrosion protection, doubtful quality control, full of explosive gas, in a vibrating, moving, salt air marine environment it was never designed for. What could possibly go wrong?

Your description is a bit of an exaggeration. My unit is made in Mexico, but similar units are made in Japan and China. It costs $145 USD. The steel cover is heavily enameled powder coating. The interior parts are of high quality and made from cast brass or other similar acceptable metals. The screws are stainless. The electronics are sealed. I rate the quality excellent. The design is such that it efficiently extracts almost all of the heat from the combustion and turns it into hot water. I can hold my hand above its exhaust outlet when it is running on high. It is not hot. There is no pilot light.

We have had four of these since 1986. They do wear out, but each iteration is better. This latest one is very nice. It withstands the vibrating, moving, salt air marine environment just fine. We circumnavigated with these devices. We always had hot water even when we rarely ran the engine. In fact we have no hot water tank and no extraction from the engine. (Did I mention simplicity and less weight?) We have had no problems with gas leaking or any other safety issues. We have had corroded electrical switches which prevented the unit from sensing the water flow and lighting. We have had water leaks. The latest one, (three years) shows no sign of these issues.

I did have an Eberspacher on my boat. It required 15 repairs in 21 months and I removed it after suing the Seattle vendor. It was easily a greater safety hazard than this water heater since it burned vaporized diesel and the hot parts were a definite fire hazard even when it was not malfunctioning.

I have also had stoves fueled by alcohol and diesel and CNG. Propane is far safer than any of these. That is in my experience, not just based on opinion.

In my opinion, this is the most foolish place to save money you could possibly come up with. Like buying seacocks made from pot metal to save a little money on bronze.

You are welcome to your opinion but don't mistake the motivation for buying these devices. It is not to save money. it is for convenience, simplicity, weight savings and safety.

Do yourself a favor and find one of the 100 other ways of making hot water on board, every one of which is at least an order of magnitude safer than this nonsense.
Care to list the 100 ways? Order of magnitude? Can you quantify that?

One dead simple way to do this is to buy the smallest Planar or Eberspacher hydronic heater and plumb it into your calorifier (or add a calorifier). Add a radiator or fan coil and you get cabin heat too. Fueled from your main tank so no extra humping of propane. Dead safe. Should cost you less than a grand all in if you do the work yourself.

Dead simple? I'll install 10 propane water heaters on propane equipped boats faster than you can install one Eberspacher, and they will still be running in five years without repairs. Try that with your diesel unit.

[Pete7]

Originally Posted by AndyEss

As for Dockhead’s disdain for propane on a boat, it is allowed by certification organizations.

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

[Dockhead]

Originally Posted by wingssail

Dockhead, You are certainly entitled to your prejudice but I disagree with it.

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?



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