Planar or even Chinese ! Diesel hot water /heaters

[ghostlymoron]

I'd plumb them in parallel with a non return valve in the flow from each heat source. I was once told that an internal combustion engine produces twice as much heat as mechanical power so that's a lot of heat available.

 

[Lucy52]

......... I was once told that an internal combustion engine produces twice as much heat as mechanical power.

Not far out, Modern diesels engines can be as much as 40 — 45% efficient, less so with older engines, so all the rest is heat in one form or another.