Iíve been trying to figure out how to properly use waste heat from my engine
and genset for a couple of years already, and still havenít figured out the right solution.
The thing is this Ė My home port is above 50 degrees N, and I spent last summer mostly above 60. Those are pretty high latitudes. I sail year around. That means I sail a lot in cold weather
, so I am constantly needing heat. Above 60N, you may need heat even in the middle of the summer. I have a pretty good central heating
system Ė a 10kW Eberspacher (Espar) hydronic furnace which makes hot water
and does space heating
through three fan coils. But I donít like to run it constantly Ė for one thing, it consumes diesel fuel
, for another, it is a somewhat high maintenance
piece of equipment
, thirdly Ė it uses electrical
power, and my boat lives on a mid-river mooring
with no shore power
When Iím at anchor
or on my mooring
in the winter time, I find myself heating water
power from my generator
, and even using electrical space heaters, just because the genset is running anyway. Which is a stupid, inefficient way to do it, even though the generator
is running anyway to charge batts. And all the while, the generator is just dumping 10kw or 20kW of heat into the ocean
has two loops in it Ė one from the central heating, one from the engine
. Iíve had the engine loop working before, but lately I havenít been able to get it to work. It seems to get an air lock which is hard to get rid of. The hoses have to curve up over a point higher than the point at which they attach to the engine Ė I guess thatís the problem. When this is not working, I find myself in the stupid situation of arriving at an anchorage with the whole crew desperately wanting a hot shower
, and there is no hot water even though the engine has just been running
So I want to solve all this somehow this winter. I thought and thought about putting in heat exchangers to transfer waste heat from both main engine and generator to the central heating circuit. Then, if I could wire up the pump to run independently from the Eberspacher, I could run the central heating system and heat water off waste heat from either engine or genset. This is a really elegant solution from a functional point of view, but I balked a bit at the complexity Ė all the hoses, heat exchangers, pumps, etc., etc.
So now Iím thinking about something simpler which might also be reasonably effective. Iím just not sure it will work, so I will be interested in expert opinions from here. What if I do the following:
1. Buy one of those bus heaters and put it in under my companionway
stairs, and plumb it into the existing engine-to-calorifier loop.
2. Put a circulation pump in that loop.
3. Put some kind of device Ė some kind of header tank maybe Ė into the high point of the hoses, so I can get the air out.
4. Create a new loop from the generator fresh water circuit, and plumb that into the engine-to-calorifier loop using diverter valves, so that I can switch the valves and put heat into the loop from either engine or generator, depending on which one is being used.
I like the fact that with this variant, there will be much less plumbing
and less hoses Ė very little more hose than what I have now. I like the fact that the bus heater is simple and separate from the existing central heating system. What I donít understand is whether it is acceptable to mix the coolant
from two engines Ė from main engine, and genset, which will happen with this scheme. I use the same coolant
in both engine and genset, and change them religiously every two years, so maybe thereís nothing wrong with commingling the coolant? What do you guys think?
Or does someone have a better scheme than either of these?
As always, grateful for sage advice.