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Thread: Questions on PIDing an HX

  1. #1
    ale
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    Questions on PIDing an HX

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi all,
    PIDing an HX has been widely discussed but since Ill use, on my expobar leva 1boiler, two solutions which are not so common, Id like to get your comments before making the final decision.

    1) I will install a PT100 sensor on the external surface of the group incoming pipe (by means of a metal tie and thermal paste). I will then thermal insulate the pipe and sensor with closed cell silicon sponge. In this way the group heating transient will shorten and the actual brewing temp will be closer to the measured one.

    2) To get good on-demand steaming capacity; rather than adjusting the PID to an higher temp., I prefer to connect the pressure-stat (set to 1.3Bar) in parallel to the SSR by means of a simple lever switch.

    Any comment is welcomed.
    Thanks



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    Re: Questions on PIDing an HX

    what "group incoming" pipe are you talking about?

    changing boiler pressure (temp) is not a suitable way of changing your shot temperature.

    The heat exchanger system in our coffee machines is already such an imprecise one due to it being a non-steady flow system most of the time, that adding a precise device such as a PID will do little to nothing for your coffees. All it will give you is deadband adjustment and a fancy looking digital display on the front of your machine, thats it.

    I think youre trying to get more out of that machine than its fundamental design will allow you to do. Not to mention that all the brass components are so heavy that they take 20+mins to reach a steady state temp.

    In my opinion, it wont work at all.

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    Senior Member GregWormald's Avatar
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    Re: Questions on PIDing an HX

    Since (IIRC) the heat in the water is proportional to the pressure, having a PID *and* a pressure-stat means two controllers for the heating element.

    Hows this supposed to work again? What would the PID be controlling?

    Greg

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    Re: Questions on PIDing an HX

    I dont see how a PID would help regulate brew water temp in a hx.* I think putting the thermocouple on the inlet pipe would help give you an idea of brew water temp after / during cooling flushes etc though. Although it still wouldnt tell you the temp of the water at the puck due to heat transfer to / from the group I guess.

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    Mal Dimal's Avatar
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    Re: Questions on PIDing an HX

    There is only one reason to opt for a PID controlled Boiler in a HX machine, rather than the ubiquitous Pressurestat, and thats convenience of adjustment for the rare occasions that adjustment may be necessary.

    There are absolutely no performance benefits to be gained and depending on how au fait you are with how to configure a PID Controller properly, performance may even be worse.

    Id stick with a high quality P/stat with the addition of an SSR to handle the switching current. This too can be stuffed up by the unwary, if you dont ensure that the switching current circumvents the Control Box, you will still be up for a new one in the not too distant future, or at the very least, a board repair to replace the relay.

    If you dont really know what you are doing with mains voltage hardware and wiring, better to let a qualified, licensed person to do all this for you.... You could go up in smoke :o

    Mal.

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    Re: Questions on PIDing an HX

    Quote Originally Posted by 577A7E727F130 link=1317373479/4#4 date=1317472408
    There is only one reason to opt for a PID controlled Boiler in a HX machine, rather than the ubiquitous Pressurestat, and thats convenience of adjustment for the rare occasions that adjustment may be necessary.

    There are absolutely no performance benefits to be gained and depending on how au fait you are with how to configure a PID Controller properly, performance may even be worse.

    Id stick with a high quality P/stat with the addition of an SSR to handle the switching current. This too can be stuffed up by the unwary, if you dont ensure that the switching current circumvents the Control Box, you will still be up for a new one in the not too distant future, or at the very least, a board repair to replace the relay.

    If you dont really know what you are doing with mains voltage hardware and wiring, better to let a qualified, licensed person to do all this for you.... You could go up in smoke :o

    Mal.
    Hi Mal,

    My only observation with the PID HX Vivi is that the PID reacts more rapidly to the change in boiler temperature than an analogue pressurestat does. The element is on immediately when you call for steam and this makes for more sustained steam than what I see from comparable pressurestat machines. This is all pretty academic as you can only texture for two milky coffees anyway.

    I am with the others in that I cannot see any benefit in placing a PID somewhere between the boiler and group in an attempt to control temperature at the group as this will continue to be dictated by HX design and any use of thermosyphon restrictors.

    Chris

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    Mal Dimal's Avatar
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    Re: Questions on PIDing an HX

    Appreciate what youre saying Chris but in my opinion itd be down to gnats whisker of difference. If the Controller installation isnt ideal and/or the Controllers configuration is also less than ideal, then all bets are off.... ;)

    Mal.

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    Re: Questions on PIDing an HX

    Quote Originally Posted by 1F32363A375B0 link=1317373479/6#6 date=1317530158
    Appreciate what youre saying Chris but in my opinion itd be down to gnats whisker of difference. If the Controller installation isnt ideal and/or the Controllers configuration is also less than ideal, then all bets are off.... ;)

    Mal.
    Too right Mal,

    I was gonna suggest a bees dicky though...[smiley=thumbsup.gif]

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    Mal Dimal's Avatar
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    Re: Questions on PIDing an HX

    Ill raise you two gnats whiskers to your one bee dicky.... ;D

    Mal.

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    ale
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    Re: Questions on PIDing an HX

    Hi all,

    I just finshed PID-ing the leva..

    installed the PT100 sensor on the external surface of boiler , underneath the thermal insulation at about boiler half height.

    connected the output of the SSR in series to the pressure stat (set at 1.3 Bar) in order to have a back-up in case of Pid or ssr* failures

    The result is satisfatorily so far, the boiler temp is kept steady at the set value...

    I tried only one cup ; no need of cooling flush and taste is quite good...






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    Re: Questions on PIDing an HX

    Quote Originally Posted by 636E67020 link=1317373479/9#9 date=1317741299
    I tried only one cup ; no need of cooling flush and taste is quite good...
    Thats because you bought a decent espresso machine, nothign to do with your PID!

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    Re: Questions on PIDing an HX

    Quote Originally Posted by 0E2A30202B22430 link=1317373479/10#10 date=1317771367
    Quote Originally Posted by 636E67020 link=1317373479/9#9 date=1317741299
    I tried only one cup ; no need of cooling flush and taste is quite good...
    Thats because you bought a decent espresso machine, nothing to do with your PID!
    Indeed, a PID on a machine like this is not only overkill, but could potentially negatively affect the shots if you dont get it set/adjusted perfectly.

    In my experience a PID on any HX machine has very little value!

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    Senior Member trentski's Avatar
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    Re: Questions on PIDing an HX

    Quote Originally Posted by 5F525B3E0 link=1317373479/9#9 date=1317741299
    I tried only one cup ; no need of cooling flush and taste is quite good...
    How is that different to the shots before the PID?

    Also are you on 110ish volts or 240ish over there?

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    Re: Questions on PIDing an HX

    I can see the benefit of a PID for a single boiler machine / dual boiler machine and for a HX with regard to steam pressure (maybe), but due to the transient nature of brew water temperature in a HX a PID on the boiler would have no real-world benefit over a pressure-stat, other than perhaps making it easier to regulate pressure / temperature of the boiler.* You are still going to have super-heated water in the heat exchanger given enough idle time regardless of the level of temp control of the boiler, or you are going to affect recovery time otherwise.

    There may be benefits of fitting a PID on a HX, but not with regard to brew water temp control. Unless I am missing something... * *

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    Mal Dimal's Avatar
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    Re: Questions on PIDing an HX

    Quote Originally Posted by 696562494B260 link=1317373479/13#13 date=1317789081
    There may be benefits of fitting a PID on a HX, but not with regard to brew water temp control.* Unless I am missing something... * *
    No mate, youre not.... ;) 8-)

    Brew Water Temp in a HX is affected more by the engineering/design of the hydraulic system than the method used to control the Boiler Water Temp. As Chris from Talk Coffee mentioned above, he noticed a slight improvement in response when the Steam Valve was cracked but otherwise, much of a muchness....

    Mal.

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    ale
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    Re: Questions on PIDing an HX

    thanks to all for the valuable info

    for the Expobar E61 the temp difference between group and boiler is 15.5 C (I made 2 measurements, with boiler temp of 109 and 107.5 C with the machine idling for 1 hour)

    Now the need of cooling flushes is much less (just a 2 seconds flushing only after long idling, otherwise no need at all). I assume the reason is the absence of temperature overrun and lower boiler temp.

    On the other hand, now the problem is the reduced steaming capacity due to lower pressure and longer pressure recovery time.

    Therefore, I plan to install a lever-swicth in series to the pressure stat and connect them in parallel to the SSR.
    By closing the switch, pressure will quickly rise to 1.3 bar and PID temp control will be temporarily excluded.
    I think that would be a good compromise.

    Bye




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    Re: Questions on PIDing an HX

    Dude, you really dont get how a heat exchanger machine works!!!

    The water for coffee comes from COLD water from the water tank. If you want to have the machine not heat up so much from idle, put a restrictor in the heat exchanger, dont lower the boiler temp

    wheres that facepalm smiley...

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    ale
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    Re: Questions on PIDing an HX

    ..I know how an HX works...

    a restrictor is not easy to be found (and even more in China where Im staying) and also the installation may not be that easy...much easier a pid even if, I agree, its not an optimal solution for an HX

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    Re: Questions on PIDing an HX

    Quote Originally Posted by 414C45200 link=1317373479/17#17 date=1318130181
    ..I know how an HX works...

    a restrictor is not easy to be found (and even more in China where Im staying) and also the installation may not be that easy...much easier a pid even if, I agree, its not an optimal solution for an HX
    A restrictor can be as simple as a brass disc with a hole in the centre. YOu can get a few hundred of them for the price of a PID.. :-?



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