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Old 05-29-2009, 05:18 AM   #1
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Sitting at the island this week, I've determined that the water heater is simply very inefficient means of heating water.

Does anyone out there have any recommendations for flash water heaters?
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Old 05-29-2009, 08:11 AM   #2
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Ken,

What would the main use of the use of the water? what temp range ?
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Old 05-29-2009, 11:53 PM   #3
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Ken,

What would the main use of the use of the water? what temp range ?
Lori needs it for showers and washing dishes. I'm just fine without it, but prefer to keep Lori happy at all costs

So, 110-120F would probably do well.

I've tried to explain to her once in the tropics, hot water will not be needed...she's not a believer.
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Old 05-30-2009, 02:03 AM   #4
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You guys never heard of a SOLAR SHOWER ??? Especially as you say you are headed into the tropics ... on days when the sun is in hiding my solar shower gets filled threequarters with cold water then 1 liter of boiling water from a kettle is added ... perfect !

Hot water for washing dishes ... ??? ... I simply have to ask WHY ??? Unless you wish to sterilise your kitchenware & to do that the water would need to be at a constant 100deg C whilst doing your washing up ... you would need asbestos-lined marigolds for that ... a good detergent such as Fairy (UK) or Dawn (US) will work in salt water & shift the greasiest of remains ... then a quick rinse in freshwater, which if you are fussy about sterility can be a mild bleach solution ... I minimise my use of fresh water by doing the final rinse with a trigger-spray bottle.

Laundry ... the same principle as a solar shower ... get a heavy duty black garbage sack ... put in your laundry with some of the aforementioned detergent & enough seawater to soak everything ... then tie the neck of the sack securely & lay it across your deck ... the sun will heat the contents & the movement of the boat will slosh everything around in a good approximation of what happens in a washing machine ... when done, wring then rinse once or twice with fresh cold water, fabric conditioner as required ... job done.
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Old 05-30-2009, 04:39 AM   #5
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Hi Ken,

Got the picture !

At one time I had an on-demand water heater - seem to remember it was made by an German aircraft company - maybe the Messerschmitt ? It was fairly large , hung vertically 30" x 12" x 6'

gas fired ! Gas always on at the tank, pilot light burning -- switch on the tap and immediately flames roared into action around a copper pipe spiral = hot water in seconds.

Probably not a good idea on a boat !!!

Tadpole suggests a solar heater - how about this one at $15 US

Solar_Shower_5_Gall.jpg

Or something like the one I have in my shower - Electric 220v - 3 kw takes about 30 seconds

to take the chill off water - maybe 110 F. Although it is 3 kw, it is not on for very long. 12" x 10" x5" - Turn on power, set temperature, turn on water = comfortable shower, here in the tropics.

Shower_Elec_on_demand3.jpg
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Old 05-30-2009, 10:13 PM   #6
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1. Solar shower. We've been using one since August 08. Works great. And, if not hot enough because no sun, etc...add a bit of boiling water to the bag.

2. Laundry--we've got a combo washer/dryer with it's own on-demand hot water heater if needed. However we wash laundry in cold water to prolong life of the clothing (even when at home).

3. Dishes--cold salt (or fresh) water wash isn't really a problem. Fresh water rinse. You can set aside my flatware in a perforated (mine is Ikea stainless steel...) drain/holder on the counter top after washing during the day. The next time you're boiling water for tea or coffee, use a cup of boiling water to get rid of any residue which may remain on the flatware. Then, put away the flatware with the other clean flatware.

4. Other sources of hot water include adding a fresh water heat exchanger to your engine and gen-set (if you use either enough for this to be valid). You can do this in series with your raw water cooling and have a very effective source of hot water. We'll be doing this with our gen set in the upcoming year or so.

5. Finally, directly use the wind generator to heat an element in a hot water tank. I've heard of other cruisers doing this as it is a great electricity dump if your batteries are already charged up.

Good luck
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Old 07-01-2009, 05:10 AM   #7
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Most marine water heaters, besides being hooked up to electricity are also hooked up to your engines fresh water cooling system. Running your engine to motor-sail, charge your batteries or enter or leave harbor also heats up your potable water tank.

I am sure your insurance company would instantly cancel your insurance if you had a gas-fired instant water heater on board. A gas flame needs a flue system - - let's see how many boats to you can find with a chimney sticking through the cabin top?

Water usage is a major concern on sailing boats with normally limited storage tanks. Many a new cruising couple have "split" when the female found out she could not "run" the water like when she was living on land. Daily showers and hair washing are not compatible with normal sailboat water tankage. Water-makers are becoming "essential" equipment when females are on board. Then there is the electrical demands of heating water and making water. That means gensets and more complexity, fuel usage and plumbing. You start to see why catamarans are becoming so popular.
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Old 07-01-2009, 03:44 PM   #8
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Most marine water heaters, besides being hooked up to electricity are also hooked up to your engines fresh water cooling system. Running your engine to motor-sail, charge your batteries or enter or leave harbor also heats up your potable water tank.

I am sure your insurance company would instantly cancel your insurance if you had a gas-fired instant water heater on board. A gas flame needs a flue system - - let's see how many boats to you can find with a chimney sticking through the cabin top?

Water usage is a major concern on sailing boats with normally limited storage tanks. Many a new cruising couple have "split" when the female found out she could not "run" the water like when she was living on land. Daily showers and hair washing are not compatible with normal sailboat water tankage. Water-makers are becoming "essential" equipment when females are on board. Then there is the electrical demands of heating water and making water. That means gensets and more complexity, fuel usage and plumbing. You start to see why catamarans are becoming so popular.
I didn't realize that most marine water heaters also included an engine heat exchanger. Of course, that's because we don't have one yet

We have two chimneys--one for a solid fuel galley stove and one for a saloon heater...ummm... the insurance company didn't care. There are numerous folks out there with similar situations.

Final umm...did you recently get divorced? If so, I'm sorry. But, please don't assume that all women are the same. It is true that almost anyone (male or female) who is dragged into the cruising lifestyle by their spouse isn't going to be happy without some of the normal amenities found at home. Also, if only one half of the couple wants to be cruising, it is only a matter of time before the couple has to deal with unhappiness that this can result in. One can't bully, guilt, or cajole someone into doing something like cruising and then wonder why they're unhappy and end up in divorce.
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Old 07-02-2009, 06:14 AM   #9
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For many years my on-board water heater was a sun-shower. It did very well on sunny calm days but when the sea was rough and there was spray the water was cold. Crew crumbled.

Last year I retired the old raw sea-water cooled engine with a new one with a dual system. Since the new engine was smaller, although slightly more powerful, then the old one I added a water heater. It is amazing. Even with a minimal use of the engine, just getting into an anchorage, there is now hot water. Problem is that the crew, including yours truly, the male skipper, is tempted to use more water.

As we all know cruising and boats are full of compromises and trade-offs.
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Old 07-02-2009, 03:40 PM   #10
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For many years my on-board water heater was a sun-shower. It did very well on sunny calm days but when the sea was rough and there was spray the water was cold. Crew crumbled.

Last year I retired the old raw sea-water cooled engine with a new one with a dual system. Since the new engine was smaller, although slightly more powerful, then the old one I added a water heater. It is amazing. Even with a minimal use of the engine, just getting into an anchorage, there is now hot water. Problem is that the crew, including yours truly, the male skipper, is tempted to use more water.

As we all know cruising and boats are full of compromises and trade-offs.
Both our engine and genset are the type with heat exchangers between antifreeze and raw water--so could have a freshwater heat exchanger added. Further, our engine has a 2.5 ft section of dry exhaust pipe that could be carry a winding of pipe or jacket around it to pull exhaust heat off as well.

We very happily use a solar shower as well. If it's cold/overcast, we just heat a little water on the stove to add to the cool water on the solar shower. We're also afraid that once we add heat exchangers to the engine and genset we'll waste too much water enjoying those showers--our fix for that is that we'll likely continue with adding hot water to the solar shower rather than actually plumbing in hot water to the shower itself.

Fair winds,

PS The only marine hot water heaters that we've seen here in the US with heat exchangers for the engine are very inefficient in terms of their design--a simple pipe going through the middle of the HW heater and a coil--the thermal efficiency looked dismal. We looked at these things because we'd like to employ radiators for a heating system (recall, we're planning on heading to higher latitudes). We figured we'd just put another heat exchanger (likely plate-and-frame) in parallel with the regular heat exchangers (on both genset and engine) and put a control valve on it to pull off engine heat. Nothing like that out there in the US. I do know of a couple radiator heating systems designed for boats but they have their own diesel heater which certainly isn't what we're looking for.
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Old 07-03-2009, 06:45 PM   #11
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There is a reason for the "inefficient" design of the engine cooling system heat transfer systems in US-made water heaters. My engine and a lot of other diesel engines run at 160F to 190F temperatures in the engine fresh water cooling system. If run long enough the water in the hot water tank would rise to that temperature and might pop open the overtemp relief valve. But basically any temperature above 105-110F delivered to a faucet or shower would result in severe burns to the human body. So by making the transfer elements in the water heater "inefficient" it greatly reduces those risks.

Since I run my main engine - a motor-sailor - all the time when at sea I added two shut-off ball valves to the hoses going to and from the water heater. They allow me to manually stop the hot engine coolant from going to the water heater to prevent over-temp'ing the water in the water heater - - and -- in case of a hose rupture/leak I can isolate the water heater from the engine.

Everybody who mentioned it is correct- the more hot water you have the more hot water you use - hot showers are soooooo good.

Down here in the Caribbean we get a lot of "new to cruising" couples who have not made the transition from land-based living to on-boat living. Water heaters, washer/dryers, TV domes, ice-makers, stand up refrigerators, etc. fill up their boats isolating them from the "organic/natural" lifestyles of "real" cruisers. It gets comical sometimes . . .

To those heating for colder - maybe Arctic - climes I installed a NEWPORT diesel cabin heater and it really pumped out some serious heat to warm up the inside of the boat with minimal fuel burn. I did install a stainless flue system with a waterproof deck fitting so that no boarding sea water could enter the chimney. Now that I am in the Caribbean I do not need the system but it worked great when I was "up-North."
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Old 07-06-2009, 05:47 AM   #12
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Well, I dunno about the reason for being inefficient being not to overload the hot water system...ummm...home hydronic heating systems have this down pat. with a combination of temperature control valve and pump...seems the same should be seen here for temperature issues.

My first job as a mechanical engineer many years ago was designing heat transfer systems in a chemical process plant--that experience taught me a lot and believe me, there are many, many ways of getting the hot water efficiently from the engine heat without messing up the engine cooling system OR messing up your desired water delivery system. As far as I can tell, the few systems I've seen here in the USA are just using simple (read "cheap") technology which may suffice simply for "one size fits all" or some such reason...

All I know for sure is, that I'd like to pull waste heat from the engine and gen-set as efficiently as possible and use it to my advantage. And, no system that I've seen on the market does it in a way that I'd like to employ in my boat. Of course, I haven't gone digging for it either.

Regarding having hot water= using it. Yes, I'd say that all our resources are that way--if you have a lot you want to use alot and if you have little, you'll be frugal. Guess that's where one has to demonstrate a little self control, eh?
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