Hydro Hot system Question - works sometimes?

steveownby wrote:
The diesel burner should be left on at all times and in the primary heating source for the boiler fluid.

This is a bit misleading. While driving, the engine will heat the boiler fluid. That boiler fluid heat can also be augmented by by the electric element.
With these systems, we normally use the diesel burner when starting from a cold tank or when heat is wanted quickly, say first thing in the morning. Or, if no electric is avail.
YMMV and you'll soon learn how to use it and under which circumstances.