Converting to hot water

[Trundlebug]

Get one that fits in the available space!

J

+1 Sounds obvious but work on the principle that you can never have too much hot water.
If weight isn't an issue (it isn't on a displacement boat) go for the biggest calorifier you can fit.

It won't affect the time it takes to have some hot water available initially - (as long as the hw take-off is at the top) and the longer you run the more you'll heat up.

The reason is, a well insulated calorifier will keep the water warm for 36-48 hours, so it extends your cruising options and comfort. If you need lots of hot water, you have it. If you want to conserve it and stay longer, you can. If you have several people staying on board, you'll always need lots of hot water. Not just for washing (showers etc) but washing up and everything else.
As it's free heat, there's no reason not to have as big a tank as you can.

Your only choice then becomes, vertical or horizontal calorifier.
The coils on vertical calorifiers are easier to bleed (self bleeding) whereas the coils on horiz tanks require a big push (more than the engine water pump can manage) to bleed the air out initially when you first plumb it in. Thereafter no problems.

 

[vyv_cox]

I am torn between fitting a replacement horizontal calorifier and looking at a diesel powered water heater. I've got an Eberspacher hot air system that works fine, so I don't have any problems with the general idea of a diesel powered system, but the cost is off-putting - 3 or 4 times the price of a replacement calorifier. But the advantage is more or less "instant" hot water; the drawback of the calorifier is that if you haven't run the engine, you don't have hot water. I don't have a mains hook up on board, and don't want one, so a calorifier with an immersion heater is not useful.

Hydronic units come up on Ebay from time to time. Current search page here shows several used ones from about £50. I have two 4 kW ones that have been assembled into one working one. I intend putting it into a small motor boat, driving a calorifier and a couple of small domestic radiators.