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Thread: PID on a HX machine?

  1. #1
    Senior Member SniffCoffee's Avatar
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    PID on a HX machine?

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I see that Bezzera make a HX machine with a PID. *Can anyone explain to me how that works? *

    Does the PID monitor the boiler temperature - which is usually the steam temp in a HX, right? *

    How then is the group head temp regulated if there isnt a pressurestat?

    Ive done a search of old threads for the last year but couldnt come up with an answer - although some people mentioned in passing that a PID wouldnt really be necessary on a HX machine?

    Yours in confusion,

    Sniff *:)

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    Senior Member Koffee_Kosmo's Avatar
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    Re: PID on a HX machine?


    Quote Originally Posted by 08160E0315160D0C620 link=1275439729/0#0 date=1275439729
    I see that Bezzera make a HX machine with a PID.Can anyone explain to me how that works?

    Does the PID monitor the boiler temperature - which is usually the steam temp in a HX, right?

    How then is the group head temp regulated if there isnt a pressurestat?

    Ive done a search of old threads for the last year but couldnt come up with an answer - although some people mentioned in passing that a PID wouldnt really be necessary on a HX machine?

    Yours in confusion
    I believe you are referring to the Bezzera BZ 07 with PID

    I am almost certain that all the BZ 07 models have an adjustable heating element inside or before the brew head in addition to the boiler element

    KK

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    Re: PID on a HX machine?

    I wouldnt have thought that there was a great need for a PID in an HX machine.

    Take the silvia for example. These machines are great with PIDs because brew temp is controlled as they dont have the stability of a big HX machine and with a small boiler its steam is more regular because there isnt that wide gap of the thermostat.

    Neither of those advantages are present in a PID HX machine. The boiler is big enough that it can take up the slack from the pressurestat gap and the thermosyphon design will keep the brew temp approximately stable as the group head temperature would stay the same as the boiler temp changes.

    I think the only advantage of a PID is that you can easily change the boiler temperature and therefore the brew and steam temperature albeit simultaneously. The other downside of an HX PIDd is that it takes time before the boiler temp change translates into brew temp change.

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    Re: PID on a HX machine?

    hehehe....

    for those people that cant handle the truth, the display on a PID machine tells them what they want to see according to what they have set, not what really is happening. Atleast for some machines.....

    They are another example of the tail wagging the dog ie the clients pushing the market to get manufacturers to give them what they want, even though they dont know anything about what they are specifying.

    Apologies as usual, for being so up front with the truth.

    Rgerdz,
    Attilio
    very first CS site sponsor

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    A_M
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    Re: PID on a HX machine?

    Quote Originally Posted by 06322533281F032F26262525400 link=1275439729/3#3 date=1275444933
    hehehe....

    for those people that cant handle the truth, the display on a PID machine tells them what they want to see according to what they have set, not what really is happening.

    They are another example of the tail wagging the dog ie the clients telling manufacturers what they want, even though they dont know anything about what they are specifying.

    Apoliogoes as usual, for being so blunt with the truth.

    Rgerdz,
    Attilio
    very first CS site sponsor
    I agree..

    MARKETING and BLING...

    Some have a place for very specific needs..

    BUT great bling.. Get the ones with the blue leds ;)

  6. #6
    Senior Member SniffCoffee's Avatar
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    Re: PID on a HX machine?

    Aaargh! :D

    Attilio, AM, stop speaking in tongues!

    If the PID is controlling the steam boiler, then how is the brew temp controlled without a pressurestat? Is there some sort of thermostat that controls the grouphead temp then? :-?

    Sniff
    PS Attilio, is the sale still on?

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    Re: PID on a HX machine?

    Sniff the pressurestat does exactly the same thing as a thermostat or PID. *Pretty sure that the pressure/temp relationship would be linear so they both achieve the same thing albeit a different way.

    As we all know the max temp of water at atmospheric pressure is 100. Under pressure the boiling point or max temp is higher so thats how a pressure stat works.

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    A_M
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    Re: PID on a HX machine?

    Quote Originally Posted by 647A626F797A61600E0 link=1275439729/5#5 date=1275445471
    Aaargh!

    Attilio, AM, stop speaking in tongues! *

    If the PID is controlling the steam boiler, then how is the brew temp controlled without a pressurestat? *Is there some sort of thermostat that controls the grouphead temp then? *
    We dont speak in tongues! .. We use KISS.

    How ever for a quick explanation..

    http://en.wikipedia.org/wiki/PID_controller

    Then look at you machine and how it all works and al the physics involved.. Ie A single boiler Vs HX etc etc Then try and decide how to wire up the PID to gain some improvement.

    In a single boiler.. Some improvement. *For many, reading a value has lots of emotional satisfaction.. *OOOhhh Arr *look 93.2156C am I not good.

    Further more trying to manage heat layers and the thermal properties between the Boiler / HX and Group is a balancing act.. *Once ya get it set up.. Great... After that; unless ya into lots of tweaking and ya taste buds are trained.. WHO cares.. BRAGGING RIGHTS.

    Oh... Now where did ya place the PID sensors.. What is their accuracy.. *Opps a big rush and lots of steam and hot water required...

    The PID can not control or manage any of that.. *That is Elements and thermal mass.. *Once stable.. Some tweaks..

    OH... 93.2156C *What ... An Audit.. Thats what the display says.. *OH.. Turn that pot / cal factor. *Oooo Cool; now it reads 63.5C *:-? *So how come my coffee tastes the same *::) ::) ::)

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    Senior Member SniffCoffee's Avatar
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    Re: PID on a HX machine?

    Well as far as I can work out there doesnt seem to be much point in a PID on a HX. If the brew water is being heated through the coil in the steam boiler then the PID would presumably always be set to the higher temperature for the steam and to have any effect on the brew temp would mean lowering the PID to the brew temp level and then raising again to steam which sort of seems to avoid the benefit of a HX in that you can steam and brew at the same time...so effectively youre turning your HX into a single boiler?

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    Re: PID on a HX machine?

    There was a great explanation on this on HomeBarista forum a while back - google it

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    Re: PID on a HX machine?

    Not sure if you understand the concept too well. If an HX machine was at normal brew boiler temp then the water coming out of the head would be far lower than ideal.

    Cold fresh brew water is heated instantly through the coil of pipes in the boiler when the brew button is pressed and the pump turns on. This is quite crude and temps would fluctuate dramatically depending on temp of the cold brew water going etc(for example if I leave my machine on the water in the tank will be quite warm so if i topped up the tank with fresh cold water that would then affect the temp of the brew water after going through the heat exchanger) The stability in an HX machine comes from the large amount of brass. HX machines have what is called a thermosyphon and this pumps water from the boiler through the group head etc. The temperature of the group assembly essentially remains stable. If you wanted to then adjust the brew temp independent to the the steam/boiler you would alter the flow of water in the thermosyphon. This is a mod that some of our sponsors do but it is not something you would change from week to week. Since the brew temp stability is dependent on the temp of the group etc so when you make a change to the boiler temp you have to wait long enough for the thermosyphon to bring the group up to temp or down to temp.

    Since a dual boiler machine has a brew boiler and the brew water is a constant temp unlike my example of above with cold vs warm tank water, that is one less variable and therefore better stability because of that.

    I hope that helps and after that rant I hope Im right but that is how I understand it.

  12. #12
    Mal Dimal's Avatar
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    Re: PID on a HX machine?

    Great post Attilio..... [smiley=tekst-toppie.gif]

    To back up what Attilio has said, in an HX espresso machine it is almost bordering on ludicrous to suggest that boiler temperature should be controlled by a PID Controller. It just makes absolutely no sense at all.

    The Primary purpose of the Boiler in a HX machine is to supply good quality Steam at preferred volumes and rate of delivery. The Brew Water Temperature is controlled, not by the temperature of the water in the Boiler so much but by the design of the Heat Exchanger system, the Group and how the water is delivered from the Boiler to the Group.

    A standard Pressurestat in a so-called Prosumer machine, will maintain Boiler Pressure at +/- 0.05Bar. This equates to a Temperature range from nominal of +/- 0.8C or expressed in another way, a peak temperature of 1.6C above the nominal setting. This is NOT the range of temperature variation reflected in the Brew Water as this is totally dependent on the HX system design as a whole. If you were to substitute the Pressurestat for a PID Controller, sure, you would be able to control the Boiler Water Temperature to a much tighter band but the only place youre going to see this (if it is at all possible) is in the Temperature of the Steam being delivered, not the Brew Water.

    If you want to attain the sense of having absolute control over the Brew Water Temperature, then you need to to start thinking decent quality Dual Boiler machines with one of the Boilers dedicated to the Brew Water. Alternatively, buy a Silvia, Quaha/Imat/Nemox/Lelit style of machine and dedicate this to pulling espresso only.

    HX espresso machines with PID Boiler Control is an absolute furphy but, if you like looking at bright LEDs and pushing buttons, then go for it..... ::)

    Mal.
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    Senior Member Koffee_Kosmo's Avatar
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    Re: PID on a HX machine?

    Snip from the Bezzera Italy web site
    http://www.bezzera.it/home_ing.html

    PID SYSTEM: on BZ07
    PID temperature control system, replaces traditional pressure switch, shows the boiler temperature on a display, the temperature can be adjusted by the user in a range from 85C to 100C .

    KK

  14. #14
    A_M
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    Re: PID on a HX machine?

    Quote Originally Posted by 56727B7B78784256726E70721D0 link=1275439729/12#12 date=1275481075
    Snip from the Bezzera Italy web site
    http://www.bezzera.it/home_ing.html

    PID SYSTEM: on BZ07
    PID temperature control system, replaces traditional pressure switch, shows the boiler temperature on a display, the temperature can be adjusted by the user in a range from 85C to 100C .

    KK
    If the unit is installed and totally replaces a manual */ bellows system; there are some gains...

    It should not be called a PID... Marketing and pandering to some section of the market..

    Does my DCM have a PID controller NO.. *

    Does it perform the same if not better functions YES..

    Because the PID is - *A generic control loop feedback mechanism; that is mass produced to allow others to use..

    A high end system will / should have its own dedicated control loop feedback mechanism that should outperform any Generic system.. *


    A little like... *many after market car products... Perform a function and when used on a car that is 20years old... Makes big difference..

    But like many after market products... Would I want the genuine ABS breaking system on my BMW or SABB or a cheep Chinese copy..

    For the old EH.. The copy will do fine and may well add something.. *With my new car... I want the system that is tailored to my car..


    OH... And I do not want 101 lights all over the place.. *People say to me.. The DCM should have a digital readout.. NOT required....

    BLING that is confusing / misleading and not required..

    But the masses love it and the marketing eat up the advertising dollars and real functionality and development, is stifled.

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    Re: PID on a HX machine?

    Quote Originally Posted by 524C54594F4C5756380 link=1275439729/8#8 date=1275457916
    Well as far as I can work out there doesnt seem to be much point in a PID on a HX
    Apart from the lack of real benifits mentioned here relating to temperature there is a couple of side benifits to having a PID/SSR (solid state relay) on a machine.

    Silence when not in use so no clicking on and off (much as some may like this to say their machine is on), no points to get earwigs under or burnout and generally easy user adjustment of the Temp from the outside of the machine while a PStat is normally covers off to get to it.

    More marketing bling than anything else I reckon. ::)

  16. #16
    A_M
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    Re: PID on a HX machine?

    Quote Originally Posted by 5B5C58575F554050575E390 link=1275439729/14#14 date=1275485498
    SSR (solid state relay) on a machine.
    The KLIIb has SSR as a reley replacement... Was a good move... But due to teh heavy current load need additional cooling.. Then teh fan started to make noises... I think coffee fines and teh odd splash from the drainer got in... And teh bearings dried and and it would squeal like a PIG...

    Still... If done right... Better that a relay and arcing contacts that generate all forts of rf noise..

    All comes back o Fit for purpose and COST ;)

  17. #17
    Mal Dimal's Avatar
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    Re: PID on a HX machine?

    Quote Originally Posted by 71555C5C5F5F6571554957553A0 link=1275439729/12#12 date=1275481075
    Snip from the Bezzera Italy web site
    http://www.bezzera.it/home_ing.html

    PID SYSTEM: on BZ07
    PID temperature control system, replaces traditional pressure switch, shows the boiler temperature on a display, the temperature can be adjusted by the user in a range from 85C to 100C .

    KK
    Youre confusing an electronic thermostat with a PID Controller KK.... Totally different kettle of fish...

    Mal.

  18. #18
    Mal Dimal's Avatar
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    Re: PID on a HX machine?

    Quote Originally Posted by 5F585C535B514454535A3D0 link=1275439729/14#14 date=1275485498
    Silence when not in use so no clicking on and off (much as some may like this to say their machine is on), no points to get earwigs under or burnout and generally easy user adjustment of the Temp from the outside of the machine while a PStat is normally covers off to get to it.
    This just isnt the case with the Mater units that most "Prosumer machine manufacturers use. It is impossible to hear the operation of one of these but maybe a young child or someone with undamaged hearing could hear the micro-relay operating.... Once again, I cant hear it.

    You are no doubt referring to a Sirai type P/stat bf and yes, for a purely domestic usage population, these are quite noisy and waayyy overkill for the intended purpose. They also suffer from a wider dead-band than the latest Mater units, not that that is a really big deal.

    On the other hand SSR installation to switch the heating element current is an excellent thing to do as the early demise of Prosumer P/stats is close to 100% due to the electrical erosion of the main contacts. This upgrade puts an end to that.

    Is an electronic T/stat a worthwhile option for P/stat replacement? My personal opinion based on several decades of working with all manner of instrumentation, electrical and electronic systems from an electrical engineering point of view, is NO. I bet the electronic T/stat in the Bezzera BZ-07 doesnt come cheap..... ::)

    Mal.

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    Re: PID on a HX machine?

    Mal,

    Re: Toppie!

    Thanks. I assume you are referring to the post immediately above yours, that mysteriously disappeared and no one can see....but if I say so myself, yes it was a toppie ;)

    I removed it because I am not sure that my straightforward / pragmatic / direct style (usually pro KISS principle), is always welcome.

    That said......Most of you blokes need to take a step back and think about the thousands of other readers that are silently looking in on this site at any one time. *The things that are written, influence what people think and ultimately what they end up buying. Too much technical stuff, some of it correct, much of it not correct.....much of it irrelevant....but it still influences those (the majority?) that dont have the skills to sort the truth from the bulldust, or the words from the acronyms.

    Someone needs to stand up and say......the topic is out of control. Of course it is a free topic board, and you blokes can carry on if you wish despite that a great proportion of readers are probably not understanding the discussion.

    Sniff:
    Mate, come on in, have a chat and I will explain. A 15 minute talk blows 24 pages of time consuming writing out of the water.

    Regardz,
    A.


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    Re: PID on a HX machine?

    Quote Originally Posted by 4F7B6C7A61564A666F6F6C6C090 link=1275439729/18#18 date=1275517724
    I removed it because I am not sure that my straightforward / pragmatic / direct style (usually pro KISS principle), is always welcome.
    So... *If it needs to be said; to bring the topic *back into perspective.. SAY IT..

    I must admit.. I actively search out your input and posts..

    WHY... Because you can often put in a post what I struggle to say in 10 posts..

    Too much going on and all to often it is about assumptions..

    KISS every time but it is hard when they dont know, what they dont know, and thus detail, is too out there...... >>>

    For me it is this post... http://coffeesnobs.com.au/YaBB.pl?num=1265274280/2#2

    Then again... How many understand, even the detail in that post...


    Quote Originally Posted by 4F7B6C7A61564A666F6F6C6C090 link=1275439729/18#18 date=1275517724
    Someone needs to stand up and say......the topic is out of control. *
    Attilio... * In addition to part 1: above; If a Person of your character and background and understanding can not speak their mind as to technical info and your experiences!!!!!!

    Then maybe I have been conned ...

    For if you do not feel comfortable in making a post, then there is something seriously wrong with the forum..


    Speak ya mind.. If you dont; the truth and or another view to consider... Will never be available to anyone. *And that would be a shame...

    PS. I thought your post was right on the nail... Not always 100% in agreement, but 100% support your approach...


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    Re: PID on a HX machine?

    From what I understand an HX system works by heating fresh cool water by passing it through piping that is passed through the boiler - thus temperature of the

    water at this stage is in relation to the boiler temperature.

    The water then enters the group system which is designed to reduce the heat to an acceptable temperature for espresso making.

    The group style is either:
    (a) thermosyphon which uses water from the boiler and depending on the flow of hot water within this system determines the temp of this system.
    (b) electrically heated.
    (c) big lump of metal which is heated by its location near the boiler.
    (d) any others??

    All these systems use a large mass of metal to obtain temperature stability and reduce the water temperature to the group temperature.

    If this is so wouldnt a hotter boiler give hotter water in the end, especially in (a) due to the thermosyphon running hotter water through it and (c)

    the group would be hotter because the boiler is hotter. Option (b) seems to be the least affected by boiler temperature.

    Do I have this totally or partially wrong.
    I dont have any experience in these at all, this is just my understanding and would like to to have it explained more.

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    A_M
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    Re: PID on a HX machine?

    Quote Originally Posted by 524940565558210 link=1275439729/20#20 date=1275528366
    I dont have any experience in these at all, this is just my understanding and would like to to have it explained more.
    Actually Of Topic and should be in another Topic..

    Been discussed a few times B4.


    1: http://www.home-barista.com/hx-love.

    and

    2: http://coffeetime.wikidot.com/heat-exchanger-machines-how-they-work

    and

    3: http://www.chriscoffee.com/faq#23

    and

    4: Do a degree in thermo dynamics and specialise in boilers etc..



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    Re: PID on a HX machine?

    Quote Originally Posted by 110A0315161B620 link=1275439729/20#20 date=1275528366
    If this is so wouldnt a hotter boiler give hotter water in the end, especially in (a) due to the thermosyphon running hotter water through it and (c)
    Yes it does, but the thermal mass of the E-61 group stabilizes it, thats why cooling flushes are needed on machines where the pressure stat is set high for increased steam (or through poor thermosyphon design i believe)

    The difference in boiler temperature is lower than most think in the on/off cycle, some relate the pressure guage to temperature directly when i believe, actual temp within the boiler only changes 2-4 degrees depending on the dead band, someone correct me if im wrong.

    I was caught up in the thought of an installation of a PID in my GPP, then through the careful guidance of the experts here, i decided it would be pure bling with very little actual difference in the cup, if any at all.

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    Re: PID on a HX machine?

    i know a pid on HX (in the boiler) is overkill but arent you just replacing a pstat with a PID and creating a tighter dead band? (and adding a SSR)

    it could be beneficial if you can keep your boiler water stable at any given temp, you can fine tune the ghead to deliver a stable water supply. cant you?

    that said, on any given day as the temp in the room goes up and down you would need to adjust the PID to compensate for the temp at the Ghead as it is directly effecting the delivery temp of the water.

    even on normal pstat e61 group heads ambient temp is going to effect it, isnt it?

    this is heading into theoretical benefits but interesting discussion

    my HX ghead bolts the boiler, I did think that controlling the boiler water temp via PID may be simpler for me than a piped thermosyphon set up machine. *I still would need 3 temp readings of one at ghead and one at boiler and one on delivery water.

    eg Ghead sitting on 85" and boiler sitting on 105" would = 93" delivery

    i could then learn to compensate Ghead temp to delivery via increasing or decreasing PID temp..... (would it work?)

    crazy idea....... ?? just thoughts really

    ps to really make it work i am going to need to heat my Ghead to keep it constant arent i = PID X 2

  25. #25
    Senior Member SniffCoffee's Avatar
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    Re: PID on a HX machine?

    Thanks everyone for their contributions and links.


    Can I summarise so far:

    1. *The PID together with a SSR in the Bezzera replaces the pressurestat. *PID keeps temp in boiler at steam level (at least above 100 degrees)

    2. *The PID gives an operating range *on the display of 85 - 100 (see KKs post and the Bezzera website)....this is less than steam level.

    3. *So presumably the PID temp is referring to brew temp at the grouphead (and in reality the PID is keeping the water temp in the boiler at least 15 degrees higher than the displayed temp to allow for steaming). *

    4. *Therefore, allowing for the flow / pressure of the water going through the HX, the boffins have calculated that the temp displayed should be the temp of the water coming out at the grouphead. *[Insert Attilios/AMs/Mals/ everyone elses qualifications to this expectation here! ::)]

    5. *Thus, the PID on the boiler is not necessarily going to overcome issues of temp surfing on a HX, but perhaps gives the user some bling to play with rather than twisting a screw on a pressurestat.

    Here endeth the lesson.

    Yours in slightly less confusion,

    Sniff *;)

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    Re: PID on a HX machine?

    Minor thing too on the Bezz it is actually an electrically heated group not thermosyphon going back to the OP machine in question so raising or lowering boiler temp will have less effect on group temp other than what is heated due to contact to the boiler.

    Without going into uni level thermodynamics and steam cycles you boiler is over 120 degrees and under pressure which keeps the bulk of the water as a liquid in the bottom of the boiler but wet steam above the water line which is the bit used for milk steaming.

    Rough chart for general info, please note this is machine specific and will vary machine to machine:

    Boiler Pressure Boiler Temp HX & Espresso Temp
    0.84 bar 117.5C 244F 88C-90C 190F-194F
    1.00 bar 120.0C 248F 90C-92C 194F-198F
    1.17 bar 122.5C 253F 92C-94C 198F-201F
    1.33 bar 125.0C 257F 94C-96C 201F-205F

  27. #27
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    Re: PID on a HX machine?

    Much of this is good and useful information, however

    Given the level of precision we are discussing in our machines, its prudent to be mindful that the user is likely to be responsible for far greater variation than any of the switching technologies were debating here...

    Its pretty easy to get all pent up about process rather than outcome, no :-?

    2mcm

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    Re: PID on a HX machine?

    Quote Originally Posted by 732C342229222E272724242C202F410 link=1275439729/26#26 date=1275536450
    Its pretty easy to get all pent up about process rather than outcome, no :-?
    2mcm
    for sure, its fun to consider but :)



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    Re: PID on a HX machine?

    Quote Originally Posted by 7671757A72786D7D7A73140 link=1275439729/25#25 date=1275536443
    Minor thing too on the Bezz it is actually an electrically heated group not thermosyphon going back to the OP machine in question so raising or lowering boiler temp will have less effect on group temp other than what is heated due to contact to the boiler.
    So if the PID is on the electrically heated grouphead then that should keep it at a pretty stable temperature even if the boiler temperature is raised or lowered and even with contact with the boiler???

  30. #30
    A_M
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    Re: PID on a HX machine?

    Quote Originally Posted by 48535A4C4F423B0 link=1275439729/28#28 date=1275538122
    So if the PID is on the electrically heated grouphead then that should keep it at a pretty stable temperature even if the boiler temperature is raised or lowered and even with contact with the boiler???
    NO and a little yes

    Just remember NO cooling so if an over shoot (deadband etc etc) then the cooling rate and control *is subject to air temp and flow.

    If ya boiler is at HOt HOT and it carries through to the group.. The PID or other controller can not cool... Just does not try to heat..

    That is why temp control on these systems is so interesting..

    If *too hot...

    One way would be to dump some boiler water and then fill. *Then one would also need to build in delays and pump / mixing actions to get the layers of hot and cold working.. Then add another delay and dead band for allowing the heat / cooling to be transferred to the rest of the system.

    Not worth it cause teh temps are not as critical as some like to think... Bigger issue is teh user ;)

    Oh and if ya think the boiler is at one temp... Forget it... there are layers and depending on temps etc .. can be interesting.. *Another reason why temp probes are at particular points and the the Heat Exchange chamber may be at a special placement.

    Just go and do the advanced Thremo dynamics at uni.. *Just ask and diver or *submariner (coms and radar etc) what temp layers can do to you...

    * the = t e h *::)

  31. #31
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    Re: PID on a HX machine?

    The PID is on the boiler not the grouphead.

    The grouphead on this machine has two small elements (PART 33 below) inserted in the brass block instead of running thermosyphoned water like an E61 head. Like my Izzo groups you also get heat transfered from the hot boiler as the group is still bolted to it as well.

    While the boiler is at say 120 degrees the actual temp of the group will be below this due to being exposed to cooler air than the 120, getting this balance right is part art part science.

    With a thermosyphon loop on the E61 style you are using the temp differential in the boiler (hot water rises) to pass a small lot of water through a loop to add to the heating of the head.


  32. #32
    Senior Member Koffee_Kosmo's Avatar
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    Re: PID on a HX machine?

    The BZ 07 does not have an E61 group head

    Heater element in the BZ 07 group head is to heat the metal part of the head to keep it at a constant temp

    There are 3 popular ways to heat up a group head that I am aware of & they are
    1 - Thermosyphon
    2 - Electric Element
    3 - Brass Bridge

    Not all machines are built the same and one should take the time to study the product before commenting on it with authority

    KK

  33. #33
    A_M
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    Re: PID on a HX machine?

    KISS

    Ya trying to manage temp control and relying on static non managed Air temp to do the cooling.

    Thus lots of smoke and mirrors and being reliant on conduction and convection as ya mediums.. * True control is from both sides.. All this is focused on one approach..

    Side of a barn door.... But it is FIT for purpose..

    And what is in the cup is what matters...

    PS. I *have to control critical incubating blocks on clinical analysers and it has to be linear across a small area *and with in *first crack.... *It is neigh on impossible and requires continuous cycling of heating / cooling blocks and variable fan control for air flow...

    All the PID and HX stuff *etc is wide open and if people think its critical and can be rock stable... They need to start teaching and lecturing the Thermo dynamic classes in uni as to the new sciences etc....

    It is BUCKET temp control at best.

  34. #34
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    Re: PID on a HX machine?

    KK - thanks for your post regarding the ways in which heads are typically heated and that the BZ07 is heated with an electrical element.

    What I would like to do is further clarify what the purpose of the PID controlled heat exchanger machine is. As stated by other esteemed colleagues, a PID on a single boiler machine such as a Rancilio Silvia is predominately focussed at improving the temperature stability. In the case of an HX machine such as the BZ07, the purpose the the PID is provide the flexibility to the user to change the temperature (ie. pressure) of the boiler (which will directly impact the temperature of the water during coffee extraction) to match different coffee blends, origins and roasts.

    By inference, increasing the temperature will increase steam availability while decreasing the temperature will decrease steam availability.

    If you require further clarification, We are only a phone call away on 1300 550 927.

    Chris
    Bezzera Australia

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    Re: PID on a HX machine?

    If the PID was on the heaters in the grouphead I would think that this would reduce the need for cooling flushes as the group wouldnt overheat (or even change temp that much) as long as it could cool itself well enough (fins maybe) when the elements were off

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    Re: PID on a HX machine?

    Shawty have a read of this http://www.home-barista.com/hx-love.html it may clear up a few things for you.

    The cooling flush is to get the water in the HX back to a more reasonable temp not nessecerilly to cool or warm the head although it will do that too. My Izzo likes a warming flush if it has been Idle for a while and is outside on a cool day.

  37. #37
    A_M
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    Re: PID on a HX machine?

    Quote Originally Posted by 3136323D353F2A3A3D34530 link=1275439729/35#35 date=1275544428
    Shawty have a read of this http://www.home-barista.com/hx-love.html it may clear up a few things for you.

    The cooling flush is to get the water in the HX back to a more reasonable temp not nessecerilly to cool or warm the head although it will do that too. My Izzo likes a warming flush if it has been Idle for a while and is outside on a cool day.
    Thanks BF..

    Provided that link and a few other; a few post previously....

    Done and dusted...


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    Re: PID on a HX machine?

    Quote Originally Posted by 6364606F676D78686F66010 link=1275439729/35#35 date=1275544428
    Shawty have a read of this http://www.home-barista.com/hx-love.html it may clear up a few things for you.

    The cooling flush is to get the water in the HX back to a more reasonable temp not nessecerilly to cool or warm the head although it will do that too. My Izzo likes a warming flush if it has been Idle for a while and is outside on a cool day.
    You must be reading my mind....
    Have just finished reading all articles AM mentioned
    Thanks to both
    This is all very interesting

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    Re: PID on a HX machine?

    Quote Originally Posted by 6D6A6E616963766661680F0 link=1275439729/35#35 date=1275544428
    My Izzo likes a warming flush if it has been Idle for a while and is outside on a cool day. *
    So the Izzo would love a PIDd element in the group to keep it warm enough when left idle on a cool day :P

  40. #40
    Senior Member Koffee_Kosmo's Avatar
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    Re: PID on a HX machine?

    I wrote a small post last week on the workings of the Heat Exchanger System in a coffee machine

    http://coffeesnobs.com.au/YaBB.pl?num=1274527580/14#14

    KK

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    Re: PID on a HX machine?

    Quote Originally Posted by 110A0315161B620 link=1275439729/38#38 date=1275546396
    PIDd element in the group to keep it warm enough when left idle on a cool day
    Nope just wouldnt be the same with a digital display or buttons to make it go beep, manual shots, manual fill is what it is and how it will stay ;) Just like a cooling flush a warming flush in my case is just getting to know the machine to get consistantly good results out of it. In my case it is just pull the lever down and run 100ml or so of water through each of the groups, even without this it still makes great shots but if I do it I get better shots again 8-)

    sorry AM the thread was getting to long and I missed your link :)

  42. #42
    A_M
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    Re: PID on a HX machine?

    Quote Originally Posted by 4245414E464C59494E47200 link=1275439729/40#40 date=1275547816
    sorry AM the thread was getting to long and I missed your link
    NA it is t e h issue with auto correction and that many dont bother or may not understand, even after reading a good article or two...

    I might do an A. and just leave it alone..

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    Re: PID on a HX machine?

    I recall watching a Barista making changes to the boiler temp on an NS Aurelia which is of course an HX machine. She had a particular blend that she felt the temp needed to be different.

    I think a PID would take the guess work out of it all. Unless you know your machine REALLY well and know EXACTLY how far to turn the screw on your PSTAT it could be a pain the the !@#$ making changes to the temp especially considering the delay as you would have to leave the machine to settle in to the new temp.

    So to the OP I reckon the idea of a PID is as crazy as some have pointed out.

  44. #44
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    Re: PID on a HX machine?

    Sorry....

    Im not convinced that any of the "Pro" arguments for PID Controlled Boiler Water Temperature on a HX machine is worthwhile. Like I said above, my background is in electrical engineering, specifically in Control Systems, SCADA and Process Control - Knowledge and experience gained over several decades with systems that are several orders of magnitude more complex than the thermodynamics of a HX Espresso Machine.

    No more posts from me....

    Mal.

  45. #45
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    Re: PID on a HX machine?

    I think that we, as snobs, or at least, coffee geeks, look at the term "PID" technically and literally. To the ignorant masses, "PID" means digital temperature control, and not much more than that.
    Kleenex vs. facial tissue
    Crescent wrench vs. adjustable spanner
    Q-tip vs. cotton swab
    PID vs. digital thermostat
    KY vs. water based lubricant
    You get the idea.

    I agree that there is little real benefit, if any, to be gained from adding a PID to a HX machine. It would add convenience of external adjustment of the temperature as well as adding the SSR to eliminate the contacts of most pressurestats (which can be done without the PID, of course).

    A properly designed HX machine can perform very well, indeed, without the PID. As an example, the brew temperature curve of the Vibiemme Domobar Super is excellent without fancy temperature control of the boiler.



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