Jacketed Boilers - What temperature do you run at?

With so many Bain Marie Boilers being used now I thought this might be a straight forward question.

What temperature do you run your jacket temperature at for your stripping run and for your spirit run? Is there an ideal scenario? ie "x" above the boiling point of the your boiler contents?

I'm looking at purchasing an 18kW steam generator and I have the option to customise the code for the unit to do exactly what I need it to. Since it's also bigger than I need for my trial unit I'll use some of the excess steam (via a heat exchanger) to make hot water.

Cheers in advanced,



  • so I can't sleep, saw this and decided 'hey, lemme google 19kw steam generator and see what TMW is looking at'..

    Check out this heating element!


    And this one...


    Mr. Steam.... hahahaha... anyone remember Mr Tea and Father Guido Sarduchi?

    160 x 120 - 5K
  • edited March 2015

    I believe the Mr Steam CU750 is a Sussman ES-18 boiler. If not, they look awfully familiar. Expensive piece of kit. Is that what you are talking about? Or one of those smaller sauna units? If sauna, watch out, many of those units have a timer that will shut them down 30 minutes in. Also, if a sauna unit, you can't return condensate, so you'll want to plumb it using something like reverse osmosis as the feed water, otherwise you are going to eventually cake it up with heavy use.

    Are you talking steam jacket (steam filled) or bain maire (liquid filled), only asking because in the case of steam, it's more common to talk about jacket pressure than temperature (although yes, both apply).

    For heat up, we are running only around 12psi, although my plumber has been beating into my head that raising the pressure significantly is not transferring more heat into the kettle. He wants to bet some serious money that heat up time will not be appreciably different at 5psi vs 12psi. Once you are into a run, very low, Probably less than 2psi. Heck I've heard guys say that once they are into the run, they turn it down until the gauge barely reads anything.

    Looking at the latent and sensible heat charts by PSI, it's pretty clear that while raising the psi is increasing the temp, the total heat energy being transmitted isn't significantly different.

    Steam Tables (PDF)

  • Thanks gents,

    It's a commercial variant of the sauna steam generator. The code is being specifically modified for my needs by the manufacturer. I'll have 3 x 6kW elements, 415v 3 phase power inlet.

    At the moment all I've asked for is continuous 100oC steam via an on/off switch. I didn't think I'd want anything more than 100oC atmospheric. This is being made for my stripping column, so I didn't specify anything less than 100oC either! I expect I'll need to descale at the end of each run.

    While I was at it I got to thinking...I could plumb this in to a jacketed boiler and use it for my spirit run. It's not enough juice for a stripping run outside of a stripping still (ie stripping via a large pot) but it's about the right amount of heat for a spirit run.

    I figured the temperature people run jackets at will depend on the products they make and the flavour profile they are trying to hit.

    In general I thought most would be aiming for as small a gradient as possible, once boiling is achieved. Just enough to do the job and no more. ie ~20-30watts per litre maximum.

    At 100oC I'd be looking at about 14.7psi. This temperature is higher than I expect and I'd have no control over it at present. My options are to include a control loop on pressure or temperature, I'm just not sure how you jacketed guys are tweaking your steam pressure throughout your run.

    I guess what I'd like to see is something like this (for example): How to run a jacketed boiler - 101

    1. Start steam to still jacket at 14psi/100oC/212oF until still contents reach 70oC
    2. At still contents = 70oC/158oF back off the steam pressure to 10psi/90oC/194oF and place the still into full reflux or wait to start collecting distillate, depending on the type of still.

    If people are making whisky using a jacketed boiler and they are running the jacket pressure/temperature differently from what I've described above please chime in.



  • edited March 2015

    With a unit like that, especially if you are able to feed it with filtered water (and no condensate return), I'd directly inject it into the still boiler (or reboiler). Just account for the additional water added during the run.

    From an efficiency perspective, it's significantly higher than an atmospheric jacket.

    That's all theoretical mind you, I've never tried it.

  • Guys I think you need to clarify which psi you are talking about. Psi or psig. Most folks talking about steam jackets are thinking of pressure ABOVE atmospheric. So this would be psig and 14 psig would be more than 100 degrees C.

  • edited March 2015

    Gauge pressure, psig.

  • I'm the noob here, looking for the clarification and guidance and how to run a jacketed boiler. I'll order the unit tonight and in a few weeks I guess I'll figure it out ;)

  • My 500l BM runs at 5psig on its own it with 24500w. If the charge gets low it might rise to 12psig before the pressure gauge starts letting out steam.

  • It may be apples to oranges, but I know that at the brewery, my jacketed 20bbl boil kettle takes just shy of twice as long to reach a rolling boil when our steam boiler is running at 8psi vs 14psi. I am still digesting your posted steam table @grim, and am by no means an expert on steam, but it does seem to me that steam at a higher temperature should release more heat upon condensation?

    I have also noticed that as we go through the brew week and the kettle gets more jacket fouling there is a noticeable decrease in efficiency, so that is something to consider as well...baked protein certainly doesn’t help heat transfer...

  • Once the steam is condensed the condensate will have a much higher deltaT if using HP steam. The interesting thing is the latent heat value drops with higher pressure making the total heat value very similar. If a trap takes the condensate away hot and your only using the latent heat then you miss out on making use of this extra Sensible? heat. Interesting. Depending on the design you might be better off with lower pressure.

    The bottom line in the chart must be supercritical, where the Latent value drops to zero? No difference between gas and liquid, cool.

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