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  • Boiler level?

    Hi,

    Is there a rule of thumb for the water level in the boiler of standard HX machines? I have the auto-fill on my Bo-Ema set to 2/3 to 3/4 full of water, and I was wondering whether it should be more/less. A Carimali that Im re-commissioning had the probe at a little over 1/2.

    TIA,
    Phil

  • #2
    Re: Boiler level?

    I there is a sight glass? Halfway between the upper and lower level should be the correct level.

    The more water, the less headroom for steam -- which is no big problem unless you tend to exhaust it all at one sitting.

    In any case, a primary concern is to ensure the element is completely enveloped by water, otherwise it burns out.

    You can easily see its location on the boiler to make sure the level is not set below.

    -Robusto

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    • #3
      Re: Boiler level?

      No, no sight glass on either, they are both autofill. Both of them have the element well and truly at the bottom, so burnout isnt really a problem.

      Its more a general question regarding a balance between production of steam and function of the HX, given that the HX runs from top to bottom. I rarely use steam in any case, so would prefer to optimise conditions for the brew temperature.

      Regards,
      Phil

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      • #4
        Re: Boiler level?

        Phil,

        The level of water in the boiler is part of the "tuning" of the HX thermal recovery -- part of the actual HX sits in the water (fast heat transfer) and part sits in the steam (slower heat transfer) and this can vary from machine to machine (of the same model) and will certainly vary from make to make. The best procedure when overhauling a commercial is to note the position of the level probe - and replace it at that position.

        So there is no "one size fits all" answer.... but as Robusto said above - make sure the elements are well and truly covered - regardless of make / model/

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        • #5
          Re: Boiler level?

          Thanks guys,

          The Bo-Ema was in such a state when it arrived, that I didnt trust the probes postion (it was pushed to the lowest point it could). The Carimali, while apparently in much better condition, also had the probe at the lowest point.....that corresponds to around half full. I plan to start it higher and work down.

          Thanks again and regards,
          Phil

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          • #6
            Re: Boiler level?

            The probe should be a pretty tight sliding fit. If the rod just about falls under its own weight, the level at which you found it may well be wrong and a new kit is in order.

            Perhaps you can look for tell-tale signs along its length: a hint of tarnish where it is exposed to the air... brighter metal where it fits in its sleeve.

            In any case, its worth removing it and cleaning up the tip. It may be encrusted with scale or other nasties which prevent completion of the earthing circuit by the water.

            As JavaB said, though, having the water set too hight --above its design level - will produce overly hot water in the heat exchangers if they were meant to be partly exposed to steam rather than water.

            Nothing wrong with finding that sweet spot yourself, though, with a trusty DMM and thermocouple.

            -Robusto

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            • #7
              Re: Boiler level?

              Definitely good advice on both counts there Robusto...

              It would be a very good starting point to replace the probe where it was and then adjust from there..... and if you follow Robustos suggestion - that should be possible. As the water height is increased you will need longer cooling flushes sooner and the brew temperature (dynamic - whilst extracting) - will increase --- and the reverse is also obviously true.

              And definitely clean the probe.... If scale prevents detection of the water.... autofill continues to fill the boiler until the OPV operates - and sprays water everywhere :-[

              Comment


              • #8
                Re: Boiler level?

                I guess its mostly been said. A coffee tech that I regularly chat to said that he places the probe as high as possible without getting wet steam. That gives you the most stored energy and fastest steam recovery. It also give the fastest HX recovery. So as JavaB said, its best to tune it until youre happy with it.

                My Pav has the probe about half way, while a commercial Bezzera 3 group (16l boiler) that I have had the probe near the top with very little head room (probably the other extreme). I also have another single group Bezzera and that uses a lower level than the 3 group, probably to give more steam volume for the smaller 5l boiler.

                Cheers,

                Mark.

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                • #9
                  Re: Boiler level?

                  The fit in the teflon tube is quite tight, even with the tightening gland completely removed. Unfortunately, there is no patina to show where the previous position was with the Carimali; I suppose I should view that as a good thing cause it means its not that old! It got descaled along with everything else and is shiny bright.

                  When I spoke to the Bo-Ema tech way back when, he also recommended a highish level. The greater thermal inertia of water compared to steam seemed to indicate to me that more than half full would be better; but as the consensus is saying, "suck it and see". As it happens, I have other woes to address before I can play around with levels.


                  Thanks,
                  Phil

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