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Heat Exchange Vs Dual boiler - Commercial

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  • Heat Exchange Vs Dual boiler - Commercial

    Okay, I thought Id split this off from another thread because I would love to debate this further, much much further. Here is the story so far:

    Originally posted by Wushoes - David S link=1197450139/15#25 date=1197555919
    Yes, very good coffee can be had from a single boiler heat exchanger. But there are a few problems with heat exchangers than La Marzocco has over these machines.

    Take for example the heat exchanger heating. Broken down, we can think of it as almost cyclical like a sine wave. So 1 in every few shots may be the "perfect" shot but every other one will either be sour or bitter. La Marzocco FB80 and GB5s have less than 0.1 deg C accuracy. La Marzocco Lineas with a 1 deg C accuracy (even with a PID on it)....but still a hell of a lot better than Heat Exchanger machines.

    I can tell you from personal experience, going from a San Marino to BFC to Azkoyen to Marzocco....there is no comparison.
    Originally posted by Pioneer Roaster link=1197450139/15#26 date=1197583138

    Firstly, unless the marzocco is PID then you will still have fluctuations. Heating water in a boiler has the same characteristics wether its a big boiler in a hx or a little boiler in a dual. The small boiler of a dual boiler machine means the fluctuations are easier to control but there is a trade off. The big down fall of all dual boilers machines is inferior (de-oxygenated) water quality due to your brew water being in contact with an element. While a good hx machine may fluctuate by a degree or two (if that) in the boiler, the hx(where water actually comes from) and group head reduce this fluctuation with each thermal transfer.

    Marzocco boards are prone to failure in the wrong hands, what is the cost these days? $2k+, not to mention down time?  
    Their are many bad machines of both type. Id take my 3 group ECM Michealangelo over a marzocco any day, try run that down or get a fluctuation.
    Originally posted by Wushoes - David S link=1197450139/30#35 date=1197599711

    My point is, even a La Marzocco Linea with a PID installed will still have a 1 degree C fluctuation. Flush a Marzocco and you get a steady stream of water....flush a HX and youll get sizzling water for a few seconds. Yes you can bring the pressure down....but that will inherently bring the brew temp down....below optimum temperature. Im not saying La Marzocco is the be all and end all. "The proof is in the cup."

    I think theres a reason why Australias top barsitas only want to work on La Marzocco and Synesso.
    Originally posted by robusto link=1197450139/30#36 date=1197600648
    What I sense here is a lot of ....snob value. (How surprising for this site!!)  
    Originally posted by GrindOnDemand link=1197450139/30#37 date=1197602449
    Well, as one of Australias top baristas, Im quite happy working on my Nuova Simonelli! ;D ;D

  • #2
    Re: Heat Exchange Vs Dual boiler - Commercial

    While I can appreciate that dual boiler machines have pros, they also have cons. As with hx machines.
    However, alot of the pros of dual boiler machines seem to be based on opinion.

    Originally posted by Wushoes - David S link=1197450139/30#35 date=1197599711
       I think theres a reason why Australias top barsitas only want to work on La Marzocco and Synesso.
    Really? Scott Callaghan??? From all talks with him he is a hx man. Anne Cooper??? bit of a generalisation dont you think. Maybe all the best baristas you know?

    Lets try keep this debate to fact.

    Not all hx machines spit steam and water. There are good ones and bad ones, as with dual boiler machines.

    Dual boilers only have good temp stabilty with PID, as does my PID hx Reneka.

    Dual boilers have no better or worse temp stability and steam recovery than an equivelant priced hx machine. There is no point comparing a marzocco to a san marino, one is twice the price. Lets compare apples with apples.

    Here are my facts in favour of hx machines.

    Espresso water from dual boilers is in contact with an element, this causing deoxygenation of the water, thus not carrying all the delicate flavours of a good espresso.  

    Dual boilers still have tracks(piping) from the boiler to the group head, this means that they may require a flush as the water can cool after leaving the boiler.


    Comment


    • #3
      Re: Heat Exchange Vs Dual boiler - Commercial

      Hey Jason,

      Im glad that you started up this topic.  Theres certainly a lot to talk about and Ill throw out some stuff to get the ball rolling ...

      In a nutshell, I think its worthwhile starting off by making a few very simple observations that Im sure that most people would agree with:

      (a) the quality of the coffee that you are using is more or less going to be determinative of the quality of the shot that you can expect, regardless of machine

      (b) HX and DB refer to one tiny feature in a whole galaxy of features in a machine; some HX machines will perform a lot better than others; some DB machines will perform a lot better than others and, finally, some HX machines will perform a lot better than some DBs (and vice-versa)

      (c) likewise, "temperature stability" is just one thing in a whole galaxy of things that make a difference to the end result

      So here are a few things that I think need to be further considered/that are pet peeves of mine.  There are a lot of clever people with experience out there and I hope that they will chime in to elaborate and correct me where necessary.

      The term "temperature stability."  

      I have three issues with this term:

      (a) Measuring temperature stability is notoriously difficult and by no means as simple as sticking your k type thermo in a filter basket or on top of your puck.  John Bicht is a professional engineer, notorious for inventing the versalab M3 espresso machine, and he gives a tiny taste of the difficulties that confront people in this thread.  For those who dont want to read the article, he shows that a typical jaycar type DVM with a K-type thermocouple will give a typical error of 7.96F (presumably from the actual/absolute value).  So, to give an example, if you get your DVM and a K-type thermocouple and get a reading of 91C and I get mine and calibrate my machine until the thermocouple reads 91C, and our measurement techniques are so spot on as to be reasonably comparable (an assumption that I reckon would be false), it would still be possible that you were brewing at 87C and I was brewing at 95C!  This means that getting  any sort of readout of an absolute value using affordable equipment is basically not going to happen.  This doesnt surprise me one iota.  In the lab at uni, the ballpark measurement equipment is always relatively cheap, but getting that extra decimal point of precision costs a hell of a lot more.

      That was absolute values.  Now lets talk about "stability."  First up, you need a datalogging thermocouple to get any sort of picture of your machines "stability."  Again, measuring isnt a simple exercise.  To get a meaningful measurement, you need to mimic the conditions that the puck will experience.  I dont have a link to a neat article by Scace, but he is the authority in the field.  He works for the US NIST (National Institute of Science and Technology, IIRC) and basically does this stuff for a living.  Many of us are familiar with the hugely expensive "scace device" that he knocked up.  I dont know how bad readings done any other way are likely to be, but I wouldnt be surprised if readings done any other way were pretty unreliable.

      It is pretty funny.  I reckon that reading all of the usual forums I have probably seen almost every single machine in the world referred to by someone as "thermo-stable" or words to that effect.  These words are almost never backed up by any mention of the measurement methodology or even the results!  Frankly, I would fall off my chair in amazement if even half of these measurements were based on any sort of half-way credible measurement.

      This is part of the reason why though I work on machines with a neat little PID readout, I have never bothered with any serious sort of thermometry.

      (b) Does temperature stability mean that the profile is as close to flat as possible?  Or does it mean repeatability?  The former seems to be closer to the natural meaning of the words.

      (c) Is there really any sort of sensible literature out there that quantifies the impact that temperature stability actually makes on a shot?  Or is it art for arts sake?

      Dont get me wrong.  I love the FB80; it is easily the best machine that I have ever used, but I dont put it all down to temperature stability ... even though I make frequent temperature adjustments!

      ...

      Comment


      • #4
        Re: Heat Exchange Vs Dual boiler - Commercial

        ... and what about the coffee?

        We seldom really get back to this. There are two things to take into account:

        (a) People have different flavour preferences. From what I have tried out over the past few years, the virtue of LM/Synesso is clarity of flavour. The virtue of e61 machines is body and mouthfeel. To be sure, there is a certain amount of tweakage that can be done, but the bottom line is that people will simply have their own preferences and it is utterly foolish to try to declare one machine to be the "best."

        (b) Different blends perform differently on different machines. I have a nice story about this. Donnie, one of the roasters at work, roasted up a few kilograms of about ten different origins and invited me to help him come up with a new blend. (Actually, I invited myself along ;P) We were using a HX machine. We went through the different candidates and created a shortlist. Then we fooled around with percentages. The last cup that we got up to on the HX was incredible - body, mouthfeel, sweetness, fruit, nut ... it had it all ... and youd bloody well hope so, after that much effort on one machine! Then our grinder broke, so we moved everything over to the FB80 and the blend simply wasnt balanced. It would have been very interesting to try out some of the origins that didnt make the shortlist on the FB80, but there is only so much coffee that the human body can take! Similarly, last week I got to visit Dean Morgan and have some shots from his Mirage, which were completely different to how they tasted on the cupping Synesso at St Ali.

        Espresso water from dual boilers is in contact with an element, this causing deoxygenation of the water, thus not carrying all the delicate flavours of a good espresso.

        This might be fact, but we need to follow the analysis through. A reduced oxygen content will merely change the relative solubility of the thousands of compounds that go into making espresso. Some of these will taste good. Some will taste bad. It would be a great experiment to do a triangle cupping using regular water in two of the cups and water with a lower oxygen content in the other. Otherwise, it might well be some other quality of the two machines that are compared that is responsible for the flavour difference. In fact, drawing water from the groups of two different machines and using it to cup probably is the only way to sensibly get some information. Ill have to try it when Im back in Melb. Thanks for the idea! Im excited!

        Dual boilers still have tracks(piping) from the boiler to the group head, this means that they may require a flush as the water can cool after leaving the boiler.
        This was, and still is, the big criticism of the Linea AV/FB70 AV (AV = volumetric). EE/semiauto machines do not have this problem, seeing as they dont have a flowmeter. Multiple boiler machines dont have this problem because the flowmeter is before the individual brew boilers. The GB5/FB80 have Pierros group caps with the flowmeter submerged into them, which fixes this problem. This is just one reason why the GB5 series is way better than the Linea series and why they are correspondingly more expensive.


        ... theres probably a book to be written on the subject, but, for now, this post will have to do. Perhaps well call it installment one ;P

        Cheers,

        Luca

        Comment


        • #5
          Re: Heat Exchange Vs Dual boiler - Commercial

          All very good stuff Luca, well worth absorbing as always.

          Just one point on the reliability of thermocouples (and the dvm for that matter). Immersing the bead into boiling water and seeing whether the reading shows 100°C should test the accuracy. For the pedants among us, that is at sea level, and of course, in an open container.

          Comment


          • #6
            Re: Heat Exchange Vs Dual boiler - Commercial

            I didnt think my posts would cause this much controversy! You lot get hung up over a bunch of nothing.

            Originally posted by Pioneer Roaster link=1197616758/0#1 date=1197617413
            Dual boilers still have tracks(piping) from the boiler to the group head, this means that they may require a flush as the water can cool after leaving the boiler.
            No such problem with the GB5/FB80. Saturated group heads with the flow meter built in for automatic machines.

            HX can never be compared to dual boiler....plain and simple....as you said...apples to apples.

            Comment


            • #7
              Re: Heat Exchange Vs Dual boiler - Commercial

              Originally posted by Pioneer Roaster link=1197616758/0#1 date=1197617413
              Lets try keep this debate to fact.

              Not all hx machines spit steam and water. There are good ones and bad ones, as with dual boiler machines.
              Yep, the only thing that "spits" steam and water on my Grimac HX is the steam wand and the hot water tap.  The groups  NEVER do.  They are very well behaved, even when sitting idle for several hours at 0.9 to 1.0 bar.

              Comment


              • #8
                Re: Heat Exchange Vs Dual boiler - Commercial

                The fact is....any cafe doing reasonable volume with extremely busy periods such as lunch and morning trade will struggle at that pressure.

                Comment


                • #9
                  Re: Heat Exchange Vs Dual boiler - Commercial

                  Even though their boilers are 5x the size of my 4L one? :-/

                  Comment


                  • #10
                    Re: Heat Exchange Vs Dual boiler - Commercial

                    Originally posted by Wushoes - David S link=1197616758/0#5 date=1197634300
                    HX can never be compared to dual boiler....plain and simple....as you said...apples to apples.
                    Agreed, nor can one be said to be better. I realise that there is no perfect machine, and both hx and dual boilers have flaws. But please leave this eliteist dual boiler machines are gods attitude at the door.
                    Like I said, Id take a hx machine anyday, its my preference.

                    As Luca said, its all about the coffee, people have different preferences, and different machines extract differently.

                    Luca, just like when I sent Jessie down some kilos of coffee and you guys could not get the profile he was used to out of it. You have got to develope blends for one type or the other. A good robust blend works well on both.

                    A mate of mine who roasts on the same roaster as me, and has a marzocco  sent me some coffee to try and when we discussed my notes he didnt believe me. He had to come over and try it on the hx himself.

                    Originally posted by Wushoes - David S link=1197616758/0#7 date=1197643643
                    The fact is....any cafe doing reasonable volume with extremely busy periods such as lunch and morning trade will struggle at that pressure.
                    Really? You had better go and tell my staff who work on the 3Gp Michealangelo with 27L boiler that draws 28 amps. They might suddenly not be able to pull 6 espresso and texture 2 big jugs of milk anymore. Or maybe the pressure needle will start to fall after the ECM reads this statement. Dont assume, what experience with high end hx machines have you had to make such a unfounded statement? What is a reasonable volume to you?

                    I once did some cuppings and testing with a custom built 4 group Cimbali with 35 L boiler and an older(new at the time) 4 group FB Marzocco, we were able to taste difference in espressos and milk drinks but as far as performace went it was niether here nor there, price was very comparable too.

                    Comment


                    • #11
                      Re: Heat Exchange Vs Dual boiler - Commercial

                      When I got my Due it was cranked up to high pressure for CAFE use even though rarely did it serve more than 4 people. I needed cooling shots when I first got it. The steam was absolutely insane from the steam wand. The cooling shots revealed a lot of dancing water after sitting for a while, and I think some steam from memory, but not much. I too knocked the pressurestat down for home use and its much better in terms of the smaller cooling flushes and only modest dancing water after a few hours.

                      Cheers

                      Comment


                      • #12
                        Re: Heat Exchange Vs Dual boiler - Commercial

                        Originally posted by Wushoes - David S link=1197616758/0#5 date=1197634300
                        I didnt think my posts would cause this much controversy! You lot get hung up over a bunch of nothing.
                        Bloody Snobs! : ;D

                        Comment


                        • #13
                          Re: Heat Exchange Vs Dual boiler - Commercial

                          "You lot"? YOU lot?

                          And I thought WE were all one big hapy family! Or was that a royal we?

                          Comment


                          • #14
                            Re: Heat Exchange Vs Dual boiler - Commercial

                            Dont you think its time for us to put our collective minds together and design our own CS machine?

                            Then again, we couldnt come to a consensus of a brew system and it would have to be scrapped.

                            Comment


                            • #15
                              Re: Heat Exchange Vs Dual boiler - Commercial

                              Originally posted by robusto link=1197616758/0#12 date=1197679042
                              "You lot"?  YOU lot?

                              And I thought WE were all one big hapy family!  Or was that a royal we?
                              Maybe one big dysfunctional family! :

                              Comment

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