Sorry to be a bit late to respond to this – I have been busy with the annual bulletin.
Can we confirm that we are talking about a blown air deisel heater such as an eberspacher or a webasto unit? I presume it isnt a vertically mounted unit such as that illustrated in Timothy’s photos? It makes a big difference.
Calista has an Eberspacher Autronic D2 mounted in the engine compartment. There is plenty of room on the starboard side aft to fit this type of heater. Atalanta engine spaces are even longer than Calista’s by the way. The inlet combustion air it taken from the engine compartment. The exhaust passes through the bulkhead into the aft cabin footwell over the top of the footwell and out of the side of the boat just below the gunwhale. The exhause is important so some detail:
It is constructed from the manufacturers stainless exhaust tube (important that you use propriatory exhaust tube intended for this type of heater). I must emphasise that the exhaust is REALLY well insulated using multiple layers of glass fibre tape intended to insulate rally car exhausts. It has an outer layer of corrugated alloy tubing to protect humans from the glass fibres. In operation it is cool enough to HOLD the outer alloy layer when the heater has been working at full power however long it has been on. The clamps on each end of the exhaust need to be checked for tightness periodically – I have known then fall off after an approved installer has finished servising a unit on a commercial vessel.
The inlet heater air is taken from the port footwell, and the heater output is ducted to the aft cabin, main cabin and forward cabin, as well as the oilskin locker. (Titanias are slightly different to Atalantas). All of the heater ducting is insulated. This model of heater has its thermostat in the heater itself. So it needs to take air from the cabin, not cold air from outside, if it is to know when to turn the heat down as the cabin heats up.
The control unit for the heater is mounted on the bulkhead inside the cabin. It has fault code reading facilities to help to maintain the heater.
Incidentally, I have found that it shuts itself down to a low output mode quite quickly, and takes less than an amp in this mode. So I have used it on long winter evenings while cruising out of season away from shore power. I dont tend to leave it on overnight – although I am sure I could.
Final comment: I chose this type of heater deliberately because I wanted to heat all areas of the boat including the aft cabin, and I wanted it to use diesel fuel. I dont think any other type would have done what I wanted.