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Thread: (Utility of) Installing a digital thermometer in a E61 group head

  1. #1
    Junior Member DavidJJ's Avatar
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    (Utility of) Installing a digital thermometer in a E61 group head

    Hi everyone,

    I have seen around several photographs of E61 machines with a digital thermometer installed in the brew head by removing the nut that is right there.
    I am in doubt if to install this and would like your opinion. Is there anyone who has already done this and obtained a real benefit?

    Simpy put, my doubt is the following: why is that thermometer supposed to help?
    I mean, I know it offers a further indication of what's happening in the machine (and specifically the brew head, which will of course be lower in temperature from what the PID shows), but what's the point in knowing that the head is at 91.5 when the PID is at 94 if I already know that a certain type of coffee (for my taste) comes out well at 94?

    Is there any specific reason to install that?
    Cheers if you can read this or if you can enlighten me

  2. #2
    Senior Member artman's Avatar
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    I agree with you. I could see a use for it to monitor / test brew temp when tuning a machine (although a scace type device would be better). Once done then it is irrelevant for a normal machine and like you say for a PID DB if you know your offset the absolute figure is irrelevant.

    But some people love gadgets (I'm one) and like gizmos! I also think it doesn't do wonders for the look of the e61 machines having a digital thermometer sticking out in the breeze.

    Cheers
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  3. #3
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    For a dual boiler with PID I understand, but for a HX set to 0.8bar boiler pressure...what's the group head temperature?

  4. #4
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    Quote Originally Posted by DavidJJ View Post
    Hi everyone,

    I have seen around several photographs of E61 machines with a digital thermometer installed in the brew head by removing the nut that is right there.
    I am in doubt if to install this and would like your opinion. Is there anyone who has already done this and obtained a real benefit?

    Simpy put, my doubt is the following: why is that thermometer supposed to help?
    I mean, I know it offers a further indication of what's happening in the machine (and specifically the brew head, which will of course be lower in temperature from what the PID shows), but what's the point in knowing that the head is at 91.5 when the PID is at 94 if I already know that a certain type of coffee (for my taste) comes out well at 94?

    Is there any specific reason to install that?
    Cheers if you can read this or if you can enlighten me
    On a DB machine with a PID I probably wouldn't bother either.
    On a Heat Exchanger machine it shows how quickly the group temperature recovers after you stop the pre-extraction flush. That gives you feedback, so you don't have to time the flush and time the recovery before you pull the shot in order to reproduce a certain temperature profile (the "hump" in the beginning).

  5. #5
    Junior Member DavidJJ's Avatar
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    Thanks everyone for the informative replies. Yes, I was mainly referring to Dual Boiler Machines already fitted with PID.
    I understand the why on HX machines. I would like to hear a discussion between the "supporters/users" of these and the "an E61 machine doesn't need a PID" group of people.
    Cheers,
    David

  6. #6
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    Quote Originally Posted by DavidJJ View Post
    Thanks everyone for the informative replies. Yes, I was mainly referring to Dual Boiler Machines already fitted with PID.
    I understand the why on HX machines. I would like to hear a discussion between the "supporters/users" of these and the "an E61 machine doesn't need a PID" group of people.
    Cheers,
    David
    I think the PID and the grouphead thermometer each serve a slightly different purpose, so one does not necessarily make the other obsolete. TBH This is not based on extensive hands-on experience, but merely on how I understand this systen is supposed to work. Sure, eventually the purpose is to control the brew temperature. However, the PID measures and controls the boiler temperature. The read-out may be either the real boiler temp or what the brew temp is expected to be at these boiler conditions. It is a point of reference, as is the pressurestat setting on a non-PIDed Heat Exchanger machine. However, the PID does not register the dynamics of how varying boiler conditions are passed to the grouphead, which is what the GH thermometer does.
    On a DB machine with an E61 head the water circulates between the brew boiler and the grouphead, so I would expect these dynamics are fairly straightforward. By flushing the group, one directs the grouphead temp up (with a lag) towards that of the brew boiler, which is controlled. On a HX machine with an E61 the temperature gradient between the boiler and the grouphead is a higher and more dynamic. By flushing, the steam pressure and thus the boiler temp drops, thereby starting a heating cycle and at the same time hot HX water is mixed with / displaced by fresh water, so it is less obvious where the group temp is going to end up. This is where the GH thermometer comes in and I feel its added value is not so much depending on whether the HX boiler is controlled by a PID or a pstat. The difference between a PID and a pstat on a HX machine is merely that with the PID the point of reference can be shifted more easily.
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  7. #7
    Mal Dimal's Avatar
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    After several years of using many types of machines, I am of the belief that that PID Controlled Brew Water Temp. coupled with an E-61 or other massive Group, is completely superfluous. The lag experienced between the time the Controller experiences a disturbance and when this correction is actually experienced at the Group Head is enormous. The only real-world benefit is the ease with which the PID Controller allows one to alter the Brew Water Boiler Setpoint, as pointed out above. The shear mass of the E-61 Group really renders the prospect of a useful integration of PID control, moot.

    If you're after truly effective PID Controlled output of the Brew water Temp., then you require a low-mass Group, an appropriate Input Power to Water Volume Ratio of the Brew Boiler and if coupled with a Group Head Heating Element, then very stable brew water temperature is possible.

    Of course, there are many ways of 'skinning a cat' in order to achieve an end-goal but PID Controllers coupled with E-61 Group machines is not the best way to go. Looks great of course but in a pure engineering sense, it doesn't make a lot of sense...

    Mal.
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  8. #8
    Senior Member Magic_Matt's Avatar
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    Quote Originally Posted by Dimal View Post
    After several years of using many types of machines, I am of the belief that that PID Controlled Brew Water Temp. coupled with an E-61 or other massive Group, is completely superfluous. The lag experienced between the time the Controller experiences a disturbance and when this correction is actually experienced at the Group Head is enormous. The only real-world benefit is the ease with which the PID Controller allows one to alter the Brew Water Boiler Setpoint, as pointed out above. The shear mass of the E-61 Group really renders the prospect of a useful integration of PID control, moot.

    If you're after truly effective PID Controlled output of the Brew water Temp., then you require a low-mass Group, an appropriate Input Power to Water Volume Ratio of the Brew Boiler and if coupled with a Group Head Heating Element, then very stable brew water temperature is possible.

    Of course, there are many ways of 'skinning a cat' in order to achieve an end-goal but PID Controllers coupled with E-61 Group machines is not the best way to go. Looks great of course but in a pure engineering sense, it doesn't make a lot of sense...

    Mal.
    All depends on usage, I guess. I tend to have a couple of milk coffees in the morning, then if working from home, an espresso or long black in the early afternoon - giving plenty of time for the group to cool (I'll typically turn the machine off in between).

    Now, if I could control the PID and steam boiler off switch remotely via Google Home, it'd be even better

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