Not Bad Chaz, close to everything you will need?
WOW alot of good advise,
concider all. It is always nice to get interesting opinions and good advise.
OK now MINE, everybody has one, OPINION which I hope will also be good advise.
As noted missing generator circuit, input(take asprin).
Most all diesel boilers are ordered with coolant pump.
As expressed, when idiling you will need it.
Good advise on the supply and return manifold ( use regular on-off valves)3 ways are expensive.
Good suggestions on the summer and winter valve.
As noted no need to close both, supply and return.
Think, Detroit supplying manifold, generator supplying manifold, webasto supplying manifold.
Of course if you have supply you need return (cold in your drawing).
Some circuits can be run in parrallell and some can be series depending on use.
Full 3/4" minimum, (prefer1" pex) from and to the manifolds. 3/4" or 1/2" pex or heater hose from there, depending on btu of the heat exchanger and load.
" It is beautiful for an engineer to shape and design the same way that an artist shapes and designs. But whether the whole process makes any sense, whether men become happier - that I can no longer decide."
Grand Pops Saying was " There is technology today to do anything the human mind can imagine." I live by that.
" WHO SAID CAN'T?
someone is always doing something
Someone else said was impossible. " unknown