Bain-Marie Pot Boiler vs Pot Belly Boiler

I have recently been looking at these two configurations.

For those whom have or have used either the Bain-Marie Pot Boiler vs. the electrical pot belly boiler, which is better and why ???

Obviously the Bain-Marie is gentler but is this really an issue ?? It also takes longer in heat up.

So if you were to start again, which one would be your preference.


  • I like the sound of the system that Swede is using.

    He has a Bain Marie that doubles up as a direct steam injector. It starts in Bain Marie mode, and then when the water in the jacket actually starts to boil, the steam is injected into the boiler charge. This combines both jacketed and steam injection modes of operation.

    Starting from scratch? It would be worth considering a Bain Marie boiler that ALSO had an immersion element directly into the boiler charge.

    As for taking longer to heat up this isn't really an issue. The bath volume is not significant compared to the boiler charge.

    What really puts a limit on the heat up time is how long it takes to transfer the energy into the boiler charge. Pump in too much energy with any boiler configuration, and you will get to a point where the energy input exceeds the rate that it can be absorbed by the boiler charge and at that point you will get burning.

  • A heat flux calculation is required to determine the running conditions.
    Maximum flux for organics = 70,000-125,000 Btu/ft2h (Kern p459)
    The practical limit for natural circulation = 12,000 Btu/ft2h
    I look to work around the 5,000-7,000 Btu/ft2h mark, but each to his own.

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