Calorifier Puzzle

[Dockhead]

My calorifier does a great job of providing piping hot showers to several people every morning when we're cruising.

As long, that is, as we have used the immersion heater either from shore power or generator power.

Running the engine doesn't seem to heat up the calorifier, although I have checked and double checked the valves.

Is it simply a matter of temperature? The water in the calorifier is held at a very high temperature, I would guess about 90C, and is mixed with cold water to provide "hot water", thus stretching the capacity. The engine fresh water cooling circuit doesn't run at 90C, so maybe it just doesn't create the same temperature?

Or is something else wrong? The calorifier has pressure relief valves or thermostats on the heat exchanger loops (see photo) which look like the ones you see on hydronic radiators. I don't know why such devices are needed. Maybe I've got them set wrong? Anyone have any ideas?

[DeepFrz]

I would suspect that your coolant from the engine isn't circulating through the calorifier (what a funny way to say "hot water tank"). Yes, the relief valves are necessary safety devices however that looks like a shutoff valve to me. This is what the hot water tank safety valve looks like.

http://www.youtube.com/watch?v=5Sm5dHAqTcI

Does it make any difference if you turn the valve from one end of travel to the other?

What temp. does your engine run at? Is it possible you need a new thermostat?

Do the coolant lines from the engine to the calorifier get hot? You should be able to tell by touch if coolant is flowing through the heat exchanger.

Have you double checked that the coolant outlet and return lines are located properly on the engine? The service manual should point out the correct locations.

[Blue Stocking]

Are the engine lines to and from the heater full of fluid, and not "air-bubbled"?

[ConradG]

Could it be that the valves are thermostatic to shut off the flow of coolant when the water temp is above the engine running temp ( or a set point) to prevent the cooler (although still hot) coolant from robbing your system of heat (and heating your engine)?? When the water is cold does the engine coolant flow?