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Gaggia Classic with PID and EM0480 - Bitter Coffee and Early Blonding?

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  • JojoS
    replied
    There are many mods and electronic mods that are toyed around with by some Gaggia Classic users. Pre-heating coils wrapped around the boiler that is connected between vibe pump and boiler plus some arduino board to trigger the boiler to turn on full power instead of PID pulsing for better intra shot temp stability. The boiler ends up with higher temp after the shot and recovery time is reported to be much much shorter. I am ok with just the PID to control starting brew temp and steam for my daily use. I make my lattes one at a time.

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  • Dimal
    replied
    Originally posted by JojoS View Post
    Getting the PID to reach SV after the shot is usually under a minute but that does not mean the temp of the water inside the boiler is stable enough for a repeatable temp shot profile. The small boiler size of 100 ml. on the Gaggia simply can not be compared with those of a Silvia or other machines with a much bigger boiler.
    Yes, you're right about that...

    And that was one of the issues which was causing me to wonder about the optimisation of the installation design. A 100ml/1,300W boiler versus a 400ml/1,200W boiler... The Gaggia should be capable of very decent performance with regards to recovery time. In fact, one of our members (going back a few years) was able to achieve the sorts of recovery (brew water Temp.) that I was referring to. I can't remember the configuration of his installation, but being a theoretical physicist, he put a lot of thought into it.

    Mal.

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  • JojoS
    replied
    Originally posted by Dimal View Post
    Hmmm...

    That time seems inordinately long for a 1,300W element Boiler using PID control. My first true espresso machine was an Imat Mokita (basically a rebadged Lelit) and this used the same sized boiler as a Silvia with a 1,200W element. With the PID values set optimally, and with an optimally located t/couple, the Mokita's recovery time was just over a minute for a double shot and always beat me locking in the Group Handle for subsequent shots.

    I think more investigation and optimisation should be pursued to improve this performance...

    Mal.
    Getting the PID to reach SV after the shot is usually under a minute but that does not mean the temp of the water inside the boiler is stable enough for a repeatable temp shot profile. The small boiler size of 100 ml. on the Gaggia simply can not be compared with those of a Silvia or other machines with a much bigger boiler.

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  • Dragunov21
    replied
    Originally posted by coffee_machinist View Post
    This thread may have some useful data for you
    If you have time to look at it, I'd be interested to know what you think of the link in post #8?

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  • Dragunov21
    replied
    Originally posted by Dimal View Post
    Hmmm...

    That time seems inordinately long for a 1,300W element Boiler using PID control. My first true espresso machine was an Imat Mokita (basically a rebadged Lelit) and this used the same sized boiler as a Silvia with a 1,200W element. With the PID values set optimally, and with an optimally located t/couple, the Mokita's recovery time was just over a minute for a double shot and always beat me locking in the Group Handle for subsequent shots.

    I think more investigation and optimisation should be pursued to improve this performance...

    Mal.
    Both element and thermocouple are mounted in the boiler housing, not the water, so there's substantial lag.

    The metal of the boiler housing heats up fast and is held at temperature, but the time it takes for the heat to transfer to the water takes a substantial amount of time (and the rate at which it does so decreases as the temperature differential decreases, I imagine).

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  • Colen001
    replied
    Thanks again to all, the thread you directed me to coffee_machinist was very insightful. From what I can gather your saying the data showed a 20 degree temp drop from the boiler to the grouphead. So in theory the best setting would be around 112 for the SV on the PID to get 92 from the grouphead. This seems high, and id assume once the boiler/grouphead are warm from say the first shot, the second and so on would be above 92 (unless recovery time is fast due to the loss of temp from the pouring of the shot). My sleeping patterns are gonna be way off from all this "testing" haha. For interest sakes I had my first attempt at roasting some beans today in a popper, so easy, so much cheaper, and of course I couldn't help myself and try a bit; a whole new level of coffee quality was experienced! Why didn't I do this years ago???

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  • Dimal
    replied
    Originally posted by JojoS View Post
    Based on Auber's testing, recovery time is about 4 minutes after pulling a shot or flushing.
    Hmmm...

    That time seems inordinately long for a 1,300W element Boiler using PID control. My first true espresso machine was an Imat Mokita (basically a rebadged Lelit) and this used the same sized boiler as a Silvia with a 1,200W element. With the PID values set optimally, and with an optimally located t/couple, the Mokita's recovery time was just over a minute for a double shot and always beat me locking in the Group Handle for subsequent shots.

    I think more investigation and optimisation should be pursued to improve this performance...

    Mal.

    Leave a comment:


  • coffee_machinist
    replied
    This thread may have some useful data for you

    Leave a comment:


  • JojoS
    replied
    Idle time will definitely impact the offset. Based on Auber's testing, recovery time is about 4 minutes after pulling a shot or flushing. There are many tricks that you can do with the Gaggia Classic and they can all be found in the Gaggia Users Forum. Some members have built a thermofilter to try to measure the brew temp as accurately as possible. I have not gone that far. I just adjust PID SV based on taste and my roast profile for a particular coffee.

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  • Dragunov21
    replied
    Originally posted by Colen001 View Post
    The thing I am wondering about the temps is, the thermocouple for the PID is attached to the outside of the boiler (washer type, where the old thermostat was) and as I have set at only 92 I am wondering if by the time it gets to the group head its probably lost 10 degree or so. Will set the PID SV to 103 and see how that goes just for interest sake.
    There should be an offset programmed in.

    The temperature will also drop substantially over the course of a shot.

    It's also worth noting that because of the boiler-mounted element/TC, you will need to let the machine rest for a substantialy period 5-15mins?) between shots, as once the heating element kicks in you'll have a massive temperature differential between the boiler housing and the water.

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  • MrJack
    replied
    Apologies Jojo, I misinterpreted what Colen had meant.

    Yes, there will be a temperature difference between the boiler external surface and the group water.

    It's likely that the boiler surface will be slightly cooler than the boiler water (and the thermocouple could be slightly cooler again, depending on how it's connected). Insulating the outside should result in a measurement closer to the water temp (note, this would actually increase the difference between the measured temp and the group temp, but should result in a more reliable measurement).

    In any case, measuring the group water temperature and the allowing an offset in the setpoint to account for the difference should give you a reasonable ball park. From there I would adjust to taste (if you can notice a difference).

    Note: You might find the required offset will vary depending on ambient temp, airflow and how long the machine has been on.

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  • Colen001
    replied
    The thing I am wondering about the temps is, the thermocouple for the PID is attached to the outside of the boiler (washer type, where the old thermostat was) and as I have set at only 92 I am wondering if by the time it gets to the group head its probably lost 10 degree or so. Will set the PID SV to 103 and see how that goes just for interest sake.

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  • MrJack
    replied
    Jojo, 103°C is boiler temp, not group temp (which is reportedly optimal at 92°C).

    Colen is asking about brew (I.e. group) temperature.

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  • JojoS
    replied
    I use 103 degrees Celsius on my Auber PID. They suggest 102. I use a triple basket that I dose with 22.6 grams of ground coffee to yield 42 grams of espresso in about 28 to 30 seconds from start of pump. I am guessing that your shots are over extracted due to channeling and brew temp too cold. Try weighing both the ground coffee and the espresso to not exceed 50% extraction. I use a Eureka Mignon Manual grinder. A bottomless portafilter will also help in pinpointing problems in the process.

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  • Colen001
    replied
    Hey folks, bit of an update, ended up trying the double basket and wow do they make a difference! Definitely a whole lot better coffee. Il see if I can get some temps today from the group head. What temperature would you all recommend? I've heard 92 is the butter zone but figured I'd get others opinions being how easy it is to set it with the PID. Thanks heaps folks

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