Domestic Hot Water - What are the options?

[alisdair4]

I am just about to buy a new (larger) boat. Problem is, she doesn't have pressurised water (good, from my perspective, as I find such systems wasteful) or a heat exchanger on the engine, so no domestic hot water. (bad, from the perspective of SWMBO)! The engine is a Volvo Penta M2DB with a raw seawater cooling system, so without re-engining there would seem no way of using the engine to heat the water. Have other forum-ites had to deal with this problem? Would a solar panel acting on a 12V immersion heater do the job, for example?

 

[Whitelighter]

Kettle?

 

[roly_voya]

You can run H/W from seawater cooling system, just take it from the engin outlet through the coil and back to the exhaust injection elbow. There is some question about seawater and tin solder so idealy should be one peice copper ellement or S/S. It will be a bit slower than with indirect cooling as the thermostat is set to about 70deg instead of about 85.

As to the engine I would check it out really carfully as they where discontinued in 1974 I believe so is over 30 years old and spares are somwhat difficult to come by - Also buy a good set of ear defenders, I kid you not, before I replaced ours you had to literally shout to be heard in the saloon when it was running although it has to be said soundproofing is always difficult on a wooden boat. I would definatly make the sort of offer that anticipated a new engine within a year or two

 

[cliff]

[ QUOTE ]
You can run H/W from seawater cooling system, just take it from the engin outlet through the coil and back to the exhaust injection elbow.

[/ QUOTE ]Duh! very wasteful ... Tap off below the stat, through a circulation pump (electric powered) to the calorifier then back to the block NOT to exhaust injection elbow. For efficient heating a circulation pump is needed on a raw water cooled engine.

As for the engine itself, agreed considering age and spares availability and "it's a volvo" - I would knock £4~5k off the price to help cover the costs of re-engining and if seller did not agree then walk away.
--------------------

"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[AIDY]

beat me too it /forums/images/graemlins/laugh.gif

 

[alisdair4]

Thanks for the advice on the hot water. As for the engine, I may have the engine model wrong, as the boat was launched in 83. But as I am in Germany, and the boat is in Scotland, checking such details is difficult! It certainly isn't particulalry noisy and seems to be in OK condition. However, survey report awaited, and the surveyor was specifically told to have good look at the engine.

 

[Anonymous]

Leaving to others the powerful arguments against the engine, have you considered gas water heating? I know several people who have this and find it much more convenient as you don't have to run the engine to make hot water. OTOH, if you are a marina boat, you don't have the benefit of being able to use electricity.

I don't have any knowledge or details of suitable gas water heaters, but I am sure others here will be able to help.

 

[angelsson]

Cliff is spot on, as usual, if you google 'calorifier' lots of info and scematic daigrams especially on the Albion water heater site (no connection with them) or any others there.

 

[headrowe]

Just fitted calorifier to raw water cooled volvo md17d after asking the forum for thier advice and opinions. Recieved some really useful information which I acted upon and am very pleased with the outcome.Took a hose from one cylinder drain plug into coil in calorifier and one back into another cylinder with a small circulating pump between.No problems so far! Many said the water would not be hot enough but I can assure you it is. We also have a paloma gas water heater which is brilliant as long as you have venting capabilities.

 

[angelsson]

Sounds ok, what sort of pump did you employ.

 

[Gunfleet]

This looks like an obvious solution to the old 1GM10 raw water problem. I hate all that warm water being wasted while I boil kettles. Could you suggest a pump Cliff?

edit - sorry, didn't read the post above.

 

[VicS]

[ QUOTE ]
Duh! very wasteful ... Tap off below the stat ......

[/ QUOTE ] Not really feasible on an MD2B to tap into the water system before the thermostat as the thermostat housing is part of the exhaust manifold. If someone were to be tempeted to tap into the hose actually below the thermostat they would be very disappointed as that is the cold water bypass!

Roly Voya's suggestion may not be the most effective as the water will not be all that hot, being a mixture of the hot water leaving the engine and cold water flowing through the bypass but it is the simplest arrangement imaginable, requiring no pumps or components other than the calorifier.

It would not be difficult to separate the bypass water, taking just the hot water from the engine (That should be about 60C) to the calorifier and combining that with the pass water between calorifier and exhaust injection. Again no extra pump required. It will need the existing bypass connection on the thermostat cover to be plugged and the fitting of a Y or T piece to combine the 2 flows.

 

[Roach1948]

[ QUOTE ]
Kettle?

[/ QUOTE ] Not such a bad idea even if you do have a hot water system. Roach, only being 22ft, I just have a one litre stainless pump action thermos bungy lashed by the sink. When I boil the kettle for any drinks I make sure I fill it up to the brim and top up my thermos. I have hot water on tap for the whole day then.

For showers I use one of those Solar things - they work really well. If it is a cloudy day, I pour some of the hot water from the thermos into that - and hey presto warm shower!

 

[alisdair4]

Apparently, the engine in the boat is a Volvo Penta md11c - sorry for the confusion. The info given has been really useful - thanks to all who replied!

 

[VicS]

[ QUOTE ]
Apparently, the engine in the boat is a Volvo Penta md11c

[/ QUOTE ] My last suggestion will definitely work with a MD11C. Disconnect the lower hose from the thermostat cover and route a replacement from the connection on the underside of the manifold to the injection elbow. Blank off the connection on the cover. Take the hose from the top of the thermostat cover to a calorifier. Take the outlet from the calorifier coil to a T or Y piece in the hose going to the injection elbow.

No pumps needed!

All the heat available will go to the calorifier and you should get a supply of water at about 60C.

 

[headrowe]

Bought a water circulating pump of ebay.Was for a mercedes sprinter van! needed something fairly inexpensive and as usual all the "marine" pumps were ££££ loaded. This was a brand new Bosch 12v pump (retail £138+ vat) bought for £27 inc postage. Identical apart from make to a friends marine pump £120+

 

[orizaba]

it might also be worth considering fitting an expansion/ pressure tank into the system to stop pulsation,not sure if it would be a problem using a calorifier but it smooths the flow and tends to help the pump out,also should give you a steady stream of hot water.
as an aside to calorifiers we,ve used for many years now both on the narrowboat and yacht a garden pressure sprayer,an old idea but worth a mention.holds 5l water,1kettle of hot ,rest cold or whatever,controllable flow,decent shower using less than 5l. water cost 10-15 squid, no sunshine needed, good for the uk