Hot water please

[A1Sailor]

I'm looking to buy a boat, and so far have been looking at ones with heat exchanged fresh water, as opposed to raw water, cooled engines - to which could be added a calorifier for hot water. (I know that it is possible to divert the exhaust raw water to do this, but it seems a step too far).
Is another way to simply have a small hot water tank with a 12volt "coil" heater - like a big kettle? This would require lots of electrical power, so would just work when the engine is running. This is obviously true about calorifiers, though.
Is it feasable? Would it work? Or is it only possible with 240volt shore power? Does anybody have any practical experience? Have you got one?

Thanks,


A1

 

[PCUK]

You can run a calorifier from raw water cooled in the same way as fresh water cooled.

 

[prv]

A 12v immersion heater run off the alternator would be technically possible, but it would be a horrendously inefficient way to heat water compared to using the waste heat from the engine. It would take away power from your battery charging ability, and possibly overheat a standard alternator which doesn't expect to power a load that keeps gobbling the full 40 amps indefinitely. You'd also be reducing the propulsive power available, especially if you decided to fix the first two problems by adding a second high-power alternator.

Basically, the idea is a non-starter for any normal sailing yacht.

Pete

 

[vyv_cox]

It is perfectly possible to run a calorifier from a raw-water cooled engine, although not by diverting the flow to the exhaust, as you suggest. There are many examples and numbers of some parts needed on my website under Engine>calorifier.

I am not aware of a 12 volt heater that could be used in this way but assuming a typical small engine electrical system the most that could be extracted from it would be little more than 500 watts. This might be achieved at the expense of quite heavy power consumption. A calorifier is a far more efficient way of generating hot water, although be aware that single cylinder engines are unlikely to produce sufficient heat to run one.

 

[A1Sailor]

As I thought.

Thanks for the responses. I'll look on Vyv's site and educate myself about the set up of raw water calorifiers. Failing which - I'll put the kettle on the stove..!

A1

 

[prv]

Failing which - I'll put the kettle on the stove..!

That's all I do.

Pete

 

[nigelmercier]

A 12v immersion heater run off the alternator would be technically possible...

Really?

 

[grumpy_o_g]

A small Hydronics/Mikuni/Webasto diesel heater would be your best bet though there are some instant gas water heaters around still (Rinnai, etc). Trouble is you're talking around £1,500 at least for diesel install I think.

 

[Csail]

Whats wrong with a rinnai?

 

[prv]

A 12v immersion heater run off the alternator would be technically possible

Really?

Sure, why not?

Wouldn't be particularly powerful, and isn't a sensible choice for all the reasons I gave, but putting a 12v heating element of suitable power in a tank of water is hardly rocket science.

Pete

 

[ffiill]

You can buy 12v immersion heaters-normally used to dump excess energy from solar powered systemsinto domestic hotwater tank.
However a calorifier is great.
My Merc OM636 will heat my tank to boiling on just a run in to harbour and it will last a couple of quick showers washing up and warm water next morning.

 

[ukmctc]

A small Hydronics/Mikuni/Webasto diesel heater would be your best bet though there are some instant gas water heaters around still (Rinnai, etc). Trouble is you're talking around £1,500 at least for diesel install I think.

Eberspacher d5ws water heater ebay £200 - £350, radiator hose, roll of it £30 and connect radiators and connect to hot water tank, which is also connected to engine, not a problem or expensive to run at 0.38 ltrs an hour, or free from engine.

 

[wizard]

Eberspacher d5ws water heater ebay £200 - £350, radiator hose, roll of it £30 and connect radiators and connect to hot water tank, which is also connected to engine, not a problem or expensive to run at 0.38 ltrs an hour, or free from engine.

I like that idea. Its something I have been thinking about for some time in order to have hot water without having to run the engine. Would one of those vehicle pre start water heaters actually work in this situation as well albeit at a slower rate of heating?

 

[rudolph_hart]

I'm looking to buy a boat, and so far have been looking at ones with heat exchanged fresh water, as opposed to raw water, cooled engines - to which could be added a calorifier for hot water. (I know that it is possible to divert the exhaust raw water to do this, but it seems a step too far).
Is another way to simply have a small hot water tank with a 12volt "coil" heater - like a big kettle? This would require lots of electrical power, so would just work when the engine is running. This is obviously true about calorifiers, though.
Is it feasable? Would it work? Or is it only possible with 240volt shore power? Does anybody have any practical experience? Have you got one?

Thanks,


A1

You could fit a gas water boiler. Our Dehler 35 was fitted with a Truma one as standard, and it does a great job. It's tucked away at the far aft end of the cockpit locker and is vented through the cockpit sidewall. In about 20 minutes, it heats 14 litres enough for Mrs Phhart to have a shower. It also has an immersion which operates when shorepower connected (not often in our case). Thermostat control looks similar to an Eberspacher unit, and ofcourse it has a separate gas stopcock.

 

[vyv_cox]

You could fit a gas water boiler. Our Dehler 35 was fitted with a Truma one as standard, and it does a great job. It's tucked away at the far aft end of the cockpit locker and is vented through the cockpit sidewall. In about 20 minutes, it heats 14 litres enough for Mrs Phhart to have a shower. It also has an immersion which operates when shorepower connected (not often in our case). Thermostat control looks similar to an Eberspacher unit, and ofcourse it has a separate gas stopcock.

Excellent kit if the one in my motorhome is anything to go by. Unfortunately yours costs £753 from a camping supplier, plus nearly £200 for all the extras required, like stopcock, exhaust hose, controller, etc. A small calorifier can be bought on Ebay for £50, plus some heater hose.

 

[warrenmarkus1]

Try Googling for Handiwash.It is basically a tank with a 12V DC element and draws around 10A, but has a 8L capacity.
They are fitted to BT vans and similar

 

[A1Sailor]

Thanks for all the responses and PMs. To summarise:
1. Calorifier is the way to go - for both Raw Water or Fresh Water Cooled engines. But a small, single cylinder engine doesn't produce enough heat to make it practicable. Might even increase wear in the engine by stopping it reaching a "normal" operating temperature.
2. Using 12volt power would need a current of ~40amps to power a 500watt element - so isn't practicable.
3. Dedicated gas water heater is expensive.
So I'll put the kettle on the gas stove!

A1

 

[Bosun Higgs]

Running a calorifier on a raw water cooled engine can be made to work but it isnt always easy or very effective.

I once had a Prout cat which had a gas powered water heater in the heads - Rinnai or something like that. It was an excellent system producing hot water on demand wherever and whenever you wanted it. Better than an engine powered system IMO.

 

[pelissima]

Thanks for all the responses and PMs. To summarise:
1. Calorifier is the way to go - for both Raw Water or Fresh Water Cooled engines. But a small, single cylinder engine doesn't produce enough heat to make it practicable. Might even increase wear in the engine by stopping it reaching a "normal" operating temperature.
2. Using 12volt power would need a current of ~40amps to power a 500watt element - so isn't practicable.
3. Dedicated gas water heater is expensive.
So I'll put the kettle on the gas stove!

A1

Recently my calorifier gave up the ghost.
I found in Athens a heat exchange for 230euros small and light which looks like the small box on the right of the picture (2 inputs-2 outputs)
http://www.heatexchangersonline.com/
Of course the engine must be running..

 

[Heckler]

Really?

Ive got a box, with a tap on one end and a big 2" threaded cap on the other, its got a 12v immersion coil inside it, it was fitted in an electric utilities van to boil water for a brew, it owes me £25 if any one wants it, its quite heavy so would cost a bit to post.
Its called a Whispaire, 12v 400w 2.5 ltrs see here http://www.whispaire.co.uk/tea-mate-wb.html
Stu
Bluddy heck, they cost £320!!