warm water off 12V

[thinwater]

12A for an hour is 0.144 KWH = about 490 BTU. 7 gallons = 58 pounds. At about 1 degree F per BTU, that's 8.5 degrees per hours or about 15 degrees in 2 hours after heating the cooler and insulation losses. 24 AH power used.

The man measured something very wrong. Less water or more amps.

No, you can't do it at the shower head. The power draw would be enormous; about 20,000 BTU/hr minimum for instant heaters. Just do the math. You learned it in high school.

---

The one assumption you are all making is that the engine can heat water. Not if the boat is outboard powered. But there aren't many outboard powered boats with that much extra power. We have a propane instant heater. Much nicer.

 

[Neeves]

Propane instant heater - another vote. Though both Thin and I had/have a Propane heater in a multihull and location and space in the 'right' location might be a real issue in a mono.

Black bag, another vote - even better 4 black bags if you want to do the washing up or laundry. Much more civilised if you are in sunny Australia (where we yearn for that wind and its cooling effect . )

The other problem not expressed (though the assumption everyone has a calorifier is close) is where are you getting all this fresh water from?

Take care, stay safe

Jonathan

 

[thinwater]

BTW, propane instant heaters must be installed correctly and must be vented. The firing rate is about 3-4 times higher than your stove or cabin heater when they are on and they put out a LOT of CO2. 25,000-30,000 BTU is typical. Think of heating all that shower water in just a few minutes, not hours.

 

[PaulRainbow]

The OP has a modest motorboat (see his avatar). He isn't going to be "sailing" in the Caribbean, Med, or Oz

He's also not going to be heating water with a vast solar array, he doesn't have one, neither does he have a big inverter or a giant battery bank, he has a pair of modest leisure batteries (he recently posted about fitting a pair of new 100ah AGMs). I am assuming that his boat has a calorifier, which may be an incorrect assumption. If it does, it's the best way of heating water, for his circumstances, IMO.

That said, as he's normally only away from shore power for a weekend, a tank full of hot water should last the weekend if used sparingly, certainly should stay hot enough for a shower at the end of day one, beginning of day two.

Finally, has man evolved to a state where he cannot manage a day without a shower ? Or wash in cold water ?

 

[Neeves]

The OP has a modest motorboat (see his avatar), fitted with a fairly sizeable inboard diesel (compared to most on here) that will be fresh water cooled. He isn't going to be "sailing" in the Caribbean, Med, or Oz

He's also not going to be heating water with a vast solar array, he doesn't have one, neither does he have a big inverter or a giant battery bank, he has a pair of modest leisure batteries (he recently posted about fitting a pair of new 100ah AGMs). I am assuming that his boat has a calorifier, which may be an incorrect assumption. If it does, it's the best way of heating water, for his circumstances, IMO.

That said, as he's normally only away from shore power for a weekend, a tank full of hot water should last the weekend if used sparingly, certainly should stay hot enough for a shower at the end of day one, beginning of day two.

Finally, has man evolved to a state where he cannot manage a day without a shower ? Or wash in cold water ?

If he has a calorifier - why is he asking the question? He obviously does not have a calorifier or his problem might be - too much hot water - as to go anywhere - he has to run his engine(s).

Man can do without a shower - granddaughters think it a birthright. If you want your granddaughter, and/or wife, to enjoy life on the water it merits catering to their whims.

Personally as I live in the 21st Century and do not want to go back to camping, as in the 60's I think having 2 showers a day, whether in Oz or Scotland should be possible. In Scotland a hot shower after an invigorating cold day on the water is as pleasant as a cool (but no need for cold) shower after a hot day in the Australian or Caribbean sun - location has no bearing.

But possibly sailors in the UK don't take their granddaughter with them on the water and pine after the 'good old days'.

Jonathan

 

[Neeves]

BTW, propane instant heaters must be installed correctly and must be vented. The firing rate is about 3-4 times higher than your stove or cabin heater when they are on and they put out a LOT of CO2. 25,000-30,000 BTU is typical. Think of heating all that shower water in just a few minutes, not hours.

Yes - ours is located against the cockpit bulkhead and vents to the cockpit - venting might be the reason they are not common on monohulls.

J

 

[Wing Mark]

I would imagine a far more efficient way to take the chill off shower water with 12v heating might be to have an element in the shower head. So only water actually used is heated. A small container ie 1 litre with heating element and thermostat to turn off the current when set water temp is reached ie when water is turned off. This way you conserve not just electricity but water also. Or perhaps a foot operated valve for water flow with switch connected. I imagine you would need a lot more current than 12amps but then for a lot shorter time. Interesting to figure the water flow min. needed and watts needed to raise temp perhaps 10 degrees.

We ahve an electric shower at home, it heats the water as you use it.
It's 10kW and it's closer to 'adequate' than 'aspirational'.

 

[AntarcticPilot]

Yes - ours is located against the cockpit bulkhead and vents to the cockpit - venting might be the reason they are not common on monohulls.

J

I think another issue is that pilot lights don't like heeling.

 

[Wing Mark]

BTW, propane instant heaters must be installed correctly and must be vented. The firing rate is about 3-4 times higher than your stove or cabin heater when they are on and they put out a LOT of CO2. 25,000-30,000 BTU is typical. Think of heating all that shower water in just a few minutes, not hours.

Is that BTU per second or what?
BTU is a unit of energy not power and it's meaningless to anyone other than plumbers and septics.

 

[Neeves]

I think another issue is that pilot lights don't like heeling.

So its a good thing our heater is on a catamaran (and in this case the OP has a Mobo that should not heel (much) . The few MoBos I have been on could relatively easily take a gas water heater as the unit could quite comfortably fit against the cockpit bulkhead (do they call it a 'cockpit') and vent through the bulkhead.

Our pilot light is only on when we need hot water, when showers, washing up etc is completed - we religiously shut off the gas to the boiler (it also saves gas . I think you can get more sophisticated boiler than ours that automatically light when there is a demand for hot water (but I might be wrong - but I vaguely recall an instant hot water system where you could here the piezo-electric light clicking on and off to light the boiler pilot... )

Noting Thins comments about being fitted by a professional - its not a difficult installation, you just need the space, the water and gas feed - all of which you can do yourself and then have it inspected. If its installed within an enclosed space - it needs a decent flow of air to the boiler. Ours is contained in an aluminium 'box' with a vented (rattan mesh), wooden, door.

Jonathan

 

[PaulRainbow]

If he has a calorifier - why is he asking the question? He obviously does not have a calorifier or his problem might be - too much hot water - as to go anywhere - he has to run his engine(s).

Man can do without a shower - granddaughters think it a birthright. If you want your granddaughter, and/or wife, to enjoy life on the water it merits catering to their whims.

Personally as I live in the 21st Century and do not want to go back to camping, as in the 60's I think having 2 showers a day, whether in Oz or Scotland should be possible. In Scotland a hot shower after an invigorating cold day on the water is as pleasant as a cool (but no need for cold) shower after a hot day in the Australian or Caribbean sun - location has no bearing.

But possibly sailors in the UK don't take their granddaughter with them on the water and pine after the 'good old days'.

Jonathan

As usual, you base your replies on the blinkered view of how you do things.

The OP has a small motorboat, he has not mentioned taking his grandchildren away to Australia on it, most likely because he doesn't have any grandchildren.

He has simply asked if the device in post #1 will give enough hot water, in 1 hour, for a quick shower. It seems everyone here has agreed that it won't and some have suggested some possible alternatives, most of us have based those alternatives on the boat that the OP has and the use to which he puts his boat.

Fitting propane heating on a trailored motorboat doesn't seem like a great solution to me.

 

[thinwater]

Is that BTU per second or what?
BTU is a unit of energy not power and it's meaningless to anyone other than plumbers and septics.

BTU/h. I wouold think also, that you would have done the conversion and switly realized that your 10KW unit is in the same general range.

Google works. All the instant units are in a similar output range. But you are, pedantically speaking, correct. We have the bad habit of referring to an XX BTU air conditioning system, when we mean BTU/h. You knew this, of course, and according to Websters my usage fell within the commonplace slang:

Despite its name, the British thermal unit, or BTU, may be more widely used in North America than in Britain. Air conditioners, furnaces, and stoves are generally rated by BTUs. (Though "BTUs" is often short for "BTUs per hour;" in air-conditioner ratings, for instance, "BTUs" really means "BTUs of cooling capacity per hour".)

So you were being a bit silly.

 

[thinwater]

Yes - ours is located against the cockpit bulkhead and vents to the cockpit - venting might be the reason they are not common on monohulls.

J

Mine is in a sealed-off bow compartment that holds only that and the holding tank. It vents through a closeable deck stack.

 

[PaulRainbow]

every one just seems to assume that everyone else has a colorifier

You are correct. I was making that "assumption" based on knowledge of the OPs boat, with it's fairly large inboard diesel. If he hasn't changed it (his avatar does show a different boat, which would be an entirely different kettle of fish ) it's one of these:

26 HT - Aquador - PDF Catalogs | Documentation | Boating Brochures

Came standard with a cold water system, hot water was an option.

 

[geem]

Is that BTU per second or what?
BTU is a unit of energy not power and it's meaningless to anyone other than plumbers and septics.

It's a British Thermal Unit used by Americans?

 

[westernman]

If you have an inboard engine, then a calorifier is really by far the best way to go. My 85 hp engine will get the water to piping hot in about 10 minutes from a cold start.

You need a lot of electricity to heat water. Doing it from batteries will knacker them pretty quickly - and how are to going to recharge them? Start the engine?
So get a calorifier. They are not complicated to install.

 

[cherod]

If you have an inboard engine, then a calorifier is really by far the best way to go. My 85 hp engine will get the water to piping hot in about 10 minutes from a cold start.

You need a lot of electricity to heat water. Doing it from batteries will knacker them pretty quickly - and how are to going to recharge them? Start the engine?
So get a calorifier. They are not complicated to install.

people seem to assume that everyone has a fresh water cooling system .
nothing to do with the OP

 

[westernman]

people seem to assume that everyone has a fresh water cooling system .
nothing to do with the OP

You can use one with a raw water cooled engine as well.
By far the most inboard engines are water cooled - not many are air cooled.

 

[Neeves]

As usual, you base your replies on the blinkered view of how you do things.

The OP has a small motorboat, he has not mentioned taking his grandchildren away to Australia on it, most likely because he doesn't have any grandchildren.

He has simply asked if the device in post #1 will give enough hot water, in 1 hour, for a quick shower. It seems everyone here has agreed that it won't and some have suggested some possible alternatives, most of us have based those alternatives on the boat that the OP has and the use to which he puts his boat.

Fitting propane heating on a trailored motorboat doesn't seem like a great solution to me.

The idea Paul, of these threads, is to provide your own experience and experiences. We don't know the OPs background we don't know his vessel. So a cross section of us offer our actual experiences, which maybe blinkered - that depends on how many vessels and different installations with which we have been involved. But if we think our views are blinkered, or being a bit less insulting, not relevant, then we may omit an idea that suits the OPs question perfectly.

I accept, fully, that offering experiences from a commercial service you will have much more knowledge of specific questions but that does not mean you have long term, hands on experiences - which in many cases might be more relevant. Thinwater installed his own gas water heater, or maybe it was a stove - he has expertise that maybe relevant (but maybe blinkered ).

So get off your high horse and allow the forum members to continue to offer their restricted views and allow the OP to filter out those suggestions that do not fit his needs.

He may have grandchildren, he may equally have a yonng wife and I personally would like them to be inclusively part of leisure on the water. Its not an SAS exercise and it is the 21st century - showers need not be a luxury. Go into a yacht club bar at the end of the day and you will find out, sadly, those that do not use showers.

Take care, stay safe

Jonathan

 

[PaulRainbow]

The idea Paul, of these threads, is to provide your own experience and experiences. We don't know the OPs background we don't know his vessel.

The OP has a moderate sized motorboat, that's trailerable. He keeps it on the East coat of the Uk. He mostly weekends, locally. His boat is fitted with 2 moderate sized domestic batteries. If he still has the Aquador 26 it has a large Volvo inboard diesel and the boat was fitted with a domestic water system as standard, hot water was an option and i'm not sure if the option was fitted. Hi avatar is of a different boat, so he may have changed to an outboard powered, small motorboat.

All of that is easily discovered and i've already mentioned most of it, more than once, but you choose to skip over it.

Do you really think, if the boat does not have an existing hot water system, that fitting a propane hot water system to a 26ft motorboat is a feasible option ?

So a cross section of us offer our actual experiences, which maybe blinkered - that depends on how many vessels and different installations with which we have been involved. But if we think our views are blinkered, or being a bit less insulting, not relevant, then we may omit an idea that suits the OPs question perfectly.

Same question, as above.

I accept, fully, that offering experiences from a commercial service you will have much more knowledge of specific questions but that does not mean you have long term, hands on experiences - which in many cases might be more relevant. Thinwater installed his own gas water heater, or maybe it was a stove - he has expertise that maybe relevant (but maybe blinkered ).

Still the same question.

So get off your high horse and allow the forum members to continue to offer their restricted views and allow the OP to filter out those suggestions that do not fit his needs.

He may have grandchildren, he may equally have a yonng wife and I personally would like them to be inclusively part of leisure on the water. Its not an SAS exercise and it is the 21st century - showers need not be a luxury. Go into a yacht club bar at the end of the day and you will find out, sadly, those that do not use showers.

More things that are not relevant to the original question. No one is suggestion not taking a shower long term, but if the OP is weekending he can have a shower the day he goes and one the day he comes back, if having hot water onboard is impossible. But then again, no one is saying it's impossible, as i said earlier, at the worst, a strip wash at the end of day one, with a sink of hot water provided by the kettle would suffice for most sensible people.

You just keep banging on about your long tern cruiser views. Not exactly the same as East coast UK weekend sailing, is it ?

As for "offering experiences from a commercial service" i don't fit plumbing systems, i'm an electrician. I do spend enough time around boats to know that systems suitable, or indeed desirable/essential, on blue water cruising yachts don't necessarily scale down to 26ft coastal motorboats based in the UK.

When someone comes along who wants to fit a blue water cruising yacht out with a domestic hot water system, perhaps even heated at times by spare solar energy, i'm sure you and the other blu water cruisers will be able to share how their systems work and it will be of great help to those who are enquiring. In the meantime, no matter how many times you bring up phantasy grandchildren and young sailing wives you need two showers a day, your systems don't scale for 26ft motorboats.

FYI, my current boat is perfectly able to have a few minor modifications and be classed as a blue water cruiser, she's already spent several years in the Med, or even somewhere a little cooler :Skipper & Delivery Services by Bob Shepton - Home Page

The boat i owned before Rainbow was a 28ft motorboat, with an inboard diesel. This had hot and cold water, shower, cooker, fridge etc and everything needed for UK coastal cruising. So i have personal experience of bot types of boat/requirements/possibilities. The difference seems to be that i can differentiate between to two completely different types of vessel and requirements/possibilities.