WATER AND SPACE HEATING SYSTEMS:
Boat fitters often specify diesel forced air (or even gas) central heating systems for new boats. These gas and diesel central heating systems can be very convenient and take up little space, BUT the diesel versions can have noisy exhausts (at night in a line of moored boats!!!) and spares can be expensive. Recently there has been a concern as to whether the red diesel available from marinas has a sufficiently high cetane rating to suit these systems. Of course the cetane issue may no longer be a problem when red diesel is abolished - but then there is the cost.  There may be scope for having two different classes of diesel on board - complicated? The initial outlay of fitting such a system can cost an arm and a leg (of course high cost items can have high profit margins - if we were cynics we might suspect that's why some boat builders like to fit them).

Contrast all of that with a relatively cheap solid fuel fire. They come in a variety of styles, some with a back boiler to heat radiators or the domestic hot water (although their strength is with their space heating, rather than as water heating systems). They provide a cheery winter glow with fuel bought, cheaply, anywhere round the canal system (or use free wood from fallen trees). A solid fuel fire draws in the cooler, water vapour laden, air at the bottom to fuel the burning process. The water content drawn in, or produced in burning, is then expelled from the fire box interior, up the chimney - providing a warm AND dry boat. It isn't a matter of whether or not water vapour is produced - The real issue is whether or not the system gets rid of the water vapour that IS produced. A boiler located under the back deck is going to do little to expel water vapour (condensation) found in the saloon or galley, whereas solid fuel fires (and drip-fed diesel systems) located in the saloon DO get rid of that condensation. Sometimes the old tried and tested solutions work better than some modern alternatives.

For Domestic water heating, a calorifier (domestic hot water tank - designed for use on a boat) can be put to good use. With a calorifier one or more coils of pipe pass through the tank containing the domestic water. Heat is transferred from the hot water in the copper coil(s) to the main body of fresh water in the tank. The hot water running through the coils could come from the engine cooling system or perhaps from the solid fuel fire back boiler (or ideally from both) - free water heating has got to be good.

Even when not cruising, we merely run the engine for an hour early in the day - batteries charge and domestic water heats up; Repeat the process in the evening before tea time - job done. When cruising, of course, it just happens anyway.  These are all just examples of the integrated system we mentioned earlier - we go into these factors in more detail on our courses:

Liveaboard Equipment  12v Charging systems  Water/Space Heating