How much power for water heating

[luke collins]

A 1kw heater will rise that by 30 oc from 10 to 40 in around an hour. Q equal mc delta T /3600. Shc of water is around 4.2.

Regarding risk you should raise it to around 60 oc around twice this engine heating or have a simple controller that has a 7 day timer and 2 stats that makes the heater raise it to 60 oc 2 times a week and by passes the 1 st stat. We do this on refrigeration heat reclaim where we only get low grade heat around 45 oc.

 

[PaulRainbow]

I should also add that heating 1L of water by 80°C takes 334.4kJ.

1 (12V) Amp hour is 43.2kJ.

Boiling a litre of water will therefore take 7.7Ah. The power of the heater will just determine how fast it will heat the water.

NB all the above figures do not take any account of efficiency losses.

Your theoretical 7.7Ah is very close to the real World 7.5Ah i posted in #21

When i first bought my last boat the hot water system was shot, i lived onboard for 3 years before i got around to fitting a new system, using the kettle in a similar way to yourself.

 

[davidej]

This thread has generated enough heat to give the OP hot water for a season.

 

[Alex_Blackwood]

You may be right. Perhaps the OP can chime in.

He is probably sitting in a darkened room somewhere, quietly sobbing!

 

[wingcommander]

Do you have a diesel hot air heater? If so these guys do a heat exchanger that will allow you heat your water from it.

If I was you if look out for an engine preheater from a landrover discovery and do some googling on the campervan YouTube's for the way to run these without a landrover...

WATER HEATERS | Bobil Vans

QUOTE]
I have one of these on order, along with a 22 ltr calorifier. Hopefully will be installed within next week or two so ile report on how good/ not so good it is . My engine is raw water cooled so ime gonna give the Bobil a try first .If its not upto expectations I may look into engine feed , though I am reluctant to push salt water through my new expensive calorifier

 

[Graham376]

QUOTE]
I have one of these on order, along with a 22 ltr calorifier. Hopefully will be installed within next week or two so ile report on how good/ not so good it is . My engine is raw water cooled so ime gonna give the Bobil a try first .If its not upto expectations I may look into engine feed , though I am reluctant to push salt water through my new expensive calorifier

You could always convert to fresh water cooling. I installed a Martec kit on an MD11C in our Berwick and it worked well. Martec - Martec / Volvo Penta

 

[mattnj]

4000w SCR

add one of these inline with the immersion heater, then you can turn up/down the load on a lower power generator....
on my old Jeanneau SO40 i have one of these for years, I ran a 1500w generator and turn the dial up till the load "sounds" about right, takes longer obviously but worked well for me...

You need to remember to turn it back to full when on shorepower or it takes a while to heat up.

 

[westernman]

Wrong forum.

 

[wingcommander]

You could always convert to fresh water cooling. I installed a Martec kit on an MD11C in our Berwick and it worked well. Martec - Martec / Volvo Penta

Not sure they do one for a Bukh 24 though.
Edit . My apologies, just seen the off engine kits....may be worthy of further investigation. Cheers

 

[catlotion]

On the hook, every two days at least I need to run the engine for an hour or so to recharge the house batteries.
That is plently to get the water tank up to well over 60C.

Do you run in gear? I'm on a swing mooring and could do with hot water but worried about boat swinging about uncontrollably...

 

[mattnj]

Do you run in gear? I'm on a swing mooring and could do with hot water but worried about boat swinging about uncontrollably...

Just run in reverse....not much happens

 

[dgadee]

Why not just run the engine at fast idle, in gear, for a while. Charge the batteries and heat the water at the same time.

Beta told me 20 mins a day at fast idle and out of gear would not be a problem if engine was used normally during other part of the day.

 

[Homer J]

I'm the OP and I am amazed (and grateful) for the amount of discussion and advice generated. In note form
1. I have abandoned the battery idea - a pity as I thought it was a good one but you have all persuaded me otherwise
2. I do run the engine and will continue to do so but I always think it is a bit antisocial and someone always gets the fumes (mid-river pontoon)
3. I will explore the option of the webasto heating water - I didn't know that was possible and would solve some of my issues
4. I'm on the South Coast - Beaulieu
5. Uses - occasional showers but can have these in the clubhouse but not keen on the trek across in PJ's in the dark, wet and cold. I'm a water waster and not marvellously efficient at washing up - some of you have amazing methods
6. I was grateful for he legionnaires and water issues advice - I have been remarkably cavalier in the past and shall mend my ways - I never drunk it though but wasn't aware of the breathing risk - I will run the hot tap until cold to empty the tank when I leave the boat
7. Thank you (especially Paul Rainbow) for all of the electrical calculations proving that my idea was fanciful. I was particularly amused by the comment that it would be lighter to bring a tank of hot water with me rather than the battery bank!
8. None of this will matter until January when I hope to be mobile enough to get onto the boat

Thank you to all of you for your help - I will think of another awful idea to get your advice on