Creative Heater Plumbing

Bill Reilly of San Francisco, California, asks:

“To increase energy efficiency onboard I am wondering if I could plumb my water heater into my generator’s cooling system so that it shares the circuit from the main engine coolant loop that heats the hot water. It seems that a couple of sturdy Y-valves and brass one-way valves would adequately isolate these two systems, which never operate at the same time. Of course, I’d use the same coolant in both systems.”

Nigel Calder replies:

What you are proposing will work just fine. You need to ensure all the hoses are fully bled so that you do not introduce any airlocks into the system that could stall coolant flow for either engine. (The cooling pumps on the freshwater side of both engines are centrifugal pumps that can get airbound.) You may also be able to get a twin heat-exchanger unit for your hot-water tank, in which case you won’t need the Y-valves and won’t have to do any valve switching. There also won’t be any mixing of the coolant from the two engines. This would simplify the installation and avoid the potential for operating errors. For example, accidentally putting the Y-valves in the wrong positions could stall the coolant flow through both engines.

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