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Thread: Temperature sensor - E61 HX or SBDU Group Head Thermometer from TTP Coffee Sensor

  1. #51
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    I've just bought one of the Coffee Sensor Pro models for my ECM Technika (rotary). This is the one that places the shaft of the thermometer into the water stream, rather than having another layer of metal, so should provide faster, less attenuated responses. It took about a week to arrive, so that's pretty good from Romania.

    First some observations: I know Tudor says it's all his own design, but it is similar looking to Eric's thermometer, although the price is substantially less. They both use a modified Taylor thermometer and a nylon/Teflon ferrule. Eric uses a two-part ferrule, while Tudor's design has a single unit. As far as I can tell the shaft is held securely by the ferrule. (Kinda important with nearly 10-bar brew pressure and 100C+ water). Tudor - if you follow this, you might want to get some help with the instructions - I think they are more geared towards your original model and don't factor in the ferrule.

    I've always gone on the flash boil plus 4 seconds flush technique for the ECM and generally have been happy with the taste I get. Being a data nerd I just wanted more!

    Now the use:
    I'm assuming use will be very similar to Eric's unit. Having read about 3-dozen threads on this topic here and and on other forums (H-B) and watching a few videos, I am still confused over the temps I should be starting & shooting for. 94C (201-202F) onto the puck seems to be the goal. (BTW - there's another thread running here: https://coffeesnobs.com.au/brewing-e...chnika-iv.html)

    The advice/instructions vary markedly between machine types (start in high 80s.... start in high 90s.... it will read 2C above the ideal puck temp... aim to be 2-under the puck temp etc etc). There is also somewhat conflicting information on what you are measuring but the most logical and consistent for my machine (ECM Technika) is that initially you are measuring group head temp and 10-15 seconds into the shot, you are measuring the brew temp water hitting the puck. There are plenty of graphs using a group head sensor and a scace. Some HX machines show the group head temp at 96/204 while the puck is showing 94/202. Graphs for my machine or Rockets mostly show a convergence to 94/202 after 10-15 seconds.... so that is what I am going for. (Thoughts welcome here!!!!!)

    After dropping my pstat to cycle between 0.9 and 1.15-bar (as per suggestions from Eric and Dan Kehn), my machine idles at around 96-97C. The Coffee Sensor is very good for letting me know when my machine is stablised and ready, rather than guessing. (Hint: much longer than I thought) The lower pstat (down from 1.4-bar) means much shorter flush/flash boiling and a further drop might mean virtually no flushing needed????

    My routine - and looking for critiques - is flush-n-go. Flush the machine until it goes up (to about 101C) and comes back down to 97/98 (hard to get precise). Load the already packed portafilter and start the shot immediately

    In the meantime, the Coffee Sensor has dropped to about 95/96. It will come back up to 97C when the shot starts, but within 10-15 seconds is stable around 94C.... which I take to be the water temp hitting the puck.

    The real test is the taste and it seems okay. I tried with a lower start temp to give a 92/93 end temp. It seemed sweeter, but I was getting variation in my grind and therefore shot length... so a few too many variables.

    BTW if you are doing a second shot within 5 minutes on the ECM, it seems it's a different technique, catching the group head temp on the way up. It's all about whether the water from the HX is taking or giving heat to the E-61 head and vice versa.

    Bottom line of a long post - the Coffee Sensor Pro seems to react quickly, and gives me a more informed coffee experience. I can see when my machine is really ready and I can get repeatable shots, as far as temp goes, rather than guessing about the length of the flash boil and flush. Is it worth the money? I am a coffee addict and a data nerd so hell yes! Is the coffee better? I'm sure it is..... isn't it?
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  3. #53
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    Follow-up on the pstat

    Just a quick separate thought on dropping the pstat to 0.9-1.15 bar..

    My flash boil lasts 2-3 seconds after an hour warm-up. Before when it was peaking at 1.4-bar (as I bought it) flash boiling would last 5-seconds+.

    The Coffee Sensor Pro showed me I was idling at just over 99C with the higher pstat. It now idles at 96/97C

    Yes it takes longer to stablise and yes it takes longer for recovery, but throwing a hand-towel over the group head when I turn the machine on seems to speed things up. I assume I might be using less power to maintain the boiler at a slightly lower temp.

    I am using less water on a cooling flush and if I drop the pstat down to peak at 1-bar (Eric's advice), maybe the cooling flush will be only a few seconds. I would be worried about losing steam pressure though. 1-bar = 99.63C, while 1.1-bar = 102.32C. You can flush down quickly but not up.
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  4. #54
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    Like you my Technika had its pstat set to about 1.4; and I also have turned it down. (I have it sitting at about 1, not sure of the range as it seems pretty tight).
    I feel like I've lost a bit of steam power; and while it does idle at a lower temp (about the same as yours) I still need to flush about the same volume of water (about 150-200ml); I'm not sure if this is related to the HX tank volume and is the amount needed before the the group sees some cooler water to start moving it down.
    I'm just glad I can now see whats going on; and I've got some chance to control it but am still wishing I had a double boiler (or a single boiler with a rotary but they don't seem to exist). I'm considering getting someone who knows what they are doing to convert it to a double boiler; but I think I'll need to save up at bit before I can afford it.

  5. #55
    Senior Member CafeLotta's Avatar
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    Quote Originally Posted by steve7 View Post
    The advice/instructions vary markedly between machine types (start in high 80s.... start in high 90s.... it will read 2C above the ideal puck temp... aim to be 2-under the puck temp etc etc). There is also somewhat conflicting information on what you are measuring but the most logical and consistent for my machine (ECM Technika) is that initially you are measuring group head temp and 10-15 seconds into the shot, you are measuring the brew temp water hitting the puck.
    The information provided on the HomeBarista website in regard to using a GroupHead thermometer on an Hx machine is probably the most comprehensive available. Eric, the creator of "Eric's Device/GroupHead thermometer" has contributed vast amounts of info there. He has stated that when Brew Water is flowing, the Grouphead Thermometer reads around 2 deg C higher than Brew Water leaving the Shower Screen. I've measured similar for my E61 single boiler.

    On an Hx machine, the balance between Steam Pressure and temperature of Brew Water leaving the Heat Exchanger will always be a balancing act in conjuction with the individual machine's thermosyphon system. Some brands/models leave the factory designed & adjusted properly, some don't. Countless user reviews attest to this. Flash boiling out of the grouphead is either too high a Pressurestat pressure setting or a thermosyphon than runs too hot at idle from my understanding and shouldn't occur but does on some machines. Either way it will temporarily overheat the E61 grouphead. I can duplicate this on my E61 Single Boiler and it will temporarily affect the Brew Water temperature if you don't allow at least a couple of minutes or more for temp to stablise again. All the theoretical talk of how stable the E61 grouphead is temp wise generally assumes a machine has been designed and adjusted correctly. Running overheated water through it or a thermosyphon running hot will temporarily have an impact on Brew Water temp from my observations.

    It will be a bit of trial and error. It's a case of finding the balance between a Pressurestat setting that doesn't compromise you're Steam pressure too much but also doesn't flash boil. If you're thermosyphon is running too hot, you may need a decent flush after sitting idle for a prolonged period and then let temp stabilise for a couple/few minutes. After that judge if you have flash boiling when running Brew Water through. The HomeBarista articles by Eric covers most of this from memory.

    You may have seen this but in case you haven't, a good reference for Hx owners -

    https://www.home-barista.com/hx-love.html

    and Eric's comments -

    https://www.home-barista.com/tips/ho...ine-t6295.html
    Last edited by CafeLotta; 4 Weeks Ago at 01:41 PM. Reason: changed E61 brewhead to grouphead. Added Links.
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  6. #56
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    Great explanation CL...

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  7. #57
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    Quote Originally Posted by CafeLotta View Post
    The information provided on the HomeBarista website in regard to using a GroupHead thermometer on an Hx machine is probably the most comprehensive available. Eric, the creator of "Eric's Device/GroupHead thermometer" has contributed vast amounts of info there. He has stated that when Brew Water is flowing, the Grouphead Thermometer reads around 2 deg C higher than Brew Water leaving the Shower Screen. I've measured similar for my E61 single boiler.

    `
    You may have seen this but in case you haven't, a good reference for Hx owners -

    https://www.home-barista.com/hx-love.html

    and Eric's comments -

    https://www.home-barista.com/tips/ho...ine-t6295.html
    CL - thanks for that. I also saw your note in the other thread. Yes I had read those & other H-B threads and found them informative, although from what I can see different machines run very different temp profiles and recovery times, so what say works for an Anita or Bezzera, doesn't apply to my Technika.

    I am clearly thick about the temperatures and how to interpret what I am observing, so here are a few follow-up questions:

    1: Is your understanding that it should be reading 2C high (eg 96C) for the whole shot or once the shot is underway for say 10-seconds that is: when Brew Water is flowing?

    In Eric's manual for his thermometer he states:
    "Indicated temperatures will be higher than those presented to the puck when using the flush-n-wait technique whereas indicated temperatures will be lower than those presented to the puck when using the flush-n-go technique"
    source: http://users.rcn.com/erics/DigThermAdptr8.pdf

    From my reading it seems I should be using the flush-n-go technique with my machine, which means indicated group head temps are lower not higher. This would suggest I should be aiming to see temperatures a couple of degrees lower than those I want at the screen.

    2: That is 92C on the gauge should mean 94C at the screen????

    3: But is that at the start and end of the shot, because the temperature doesn't stay constant?

    Then there are those who show graphs and say the temps converge after 10 seconds anyway, so it is 94C after 10-seconds, that is what I should be looking for.

    4: But - does that apply to my machine.

    Sorry you responded now????

  8. #58
    Senior Member CafeLotta's Avatar
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    Quote Originally Posted by steve7 View Post
    CL - thanks for that. I also saw your note in the other thread. Yes I had read those & other H-B threads and found them informative, although from what I can see different machines run very different temp profiles and recovery times, so what say works for an Anita or Bezzera, doesn't apply to my Technika.

    I am clearly thick about the temperatures and how to interpret what I am observing, so here are a few follow-up questions:

    1: Is your understanding that it should be reading 2C high (eg 96C) for the whole shot or once the shot is underway for say 10-seconds that is: when Brew Water is flowing?

    In Eric's manual for his thermometer he states:
    "Indicated temperatures will be higher than those presented to the puck when using the flush-n-wait technique whereas indicated temperatures will be lower than those presented to the puck when using the flush-n-go technique"
    source: http://users.rcn.com/erics/DigThermAdptr8.pdf

    From my reading it seems I should be using the flush-n-go technique with my machine, which means indicated group head temps are lower not higher. This would suggest I should be aiming to see temperatures a couple of degrees lower than those I want at the screen.

    2: That is 92C on the gauge should mean 94C at the screen????

    3: But is that at the start and end of the shot, because the temperature doesn't stay constant?

    Then there are those who show graphs and say the temps converge after 10 seconds anyway, so it is 94C after 10-seconds, that is what I should be looking for.

    4: But - does that apply to my machine.

    Sorry you responded now????
    Apologies, I only just now revisited this thread and saw your questions.

    To Q1 - I can only comment on my experience with a Grouphead thermometer on an E61 Single Boiler (SBDU non HX). My Thermosyphon runs cold so the compromise I use is a sort of Flush and Wait routine. My thermostat is purposely set on the low side (due to deadband) and I need to temp surf. A couple of flushes and then Brew when my heating light goes out and Thermometer shows correct temp to start brew. When I start, I get a momentary spike showing on the thermometer which after 1 or 2 secs quickly settles to a fairly stable brew temp. It's not static but only varies between 0.3 to 1(max) deg C during the brew duration. It took a while and various thermostat adjustments to find what works for me. The 2nd shot needs a little longer wait after the light goes out.

    There are quite a few videos on YouTube for Hx machines with Grouphead Thermometers. Generally they show a momentary Temp Spike of 1 or 2 secs then settle to a brew temp which is fairly tight but not totally static.

    To Q2 - I am only aware of the Grouphead Thermometer showing flowing Brew-water at 2 deg C (nom) higher than water hitting the puck.

    There may be an instance on an Hx machine where flushed overheated water from the Exchanger momentarily overheats the E61 Grouphead, diffuser and Shower Screen. If using Flush and Go, this might then in turn heat up the small volume of water of a shot as it flows through the Grouphead and heat transfers from the hotter Grouphead etc to the lower temp Brew-water. The Grouphead thermometer would show the now slightly lower temp water coming from the Exchanger which in turn is slightly heated on it's way through the Grouphead. The only time I could imagine this happens is if your Thermosyphon is running quite hot or upon reflection, your Pressurestat is set too high (possibly). That's the way I see it anyway. I haven't read all the Hx content on Home Barista so it may be covered there or another reason may be given.

    To Q3 - As mentioned in my answer to Q1, I see a momentary 1 to 2 sec spike as Brew-water first hits the thermometer. If I've hit my routine correctly, it spikes around 2-3 deg C, if not then up to a 5 deg C spike. After the spike it will immediately settle to around my desired Brewing Temp. As the shot progresses, it will slowly drop. If I'm on my correct routine, around 0.5 deg C drop. If not, up to 1 deg C or slightly more.

    So for instance, on my machine after a full warm-up, I'll aim to idle at around 93 deg C after a flush or two and 1 minute wait. Activate Brew Lever, temp spikes to 97-98 for 1 sec (maybe 2), settles immediately to around 96 deg then slowly drops to say around 95.5 deg C at end. This gives Brew-water at the puck of 94-93.5 deg C during the shot. Adjusting the initial flush and starting idle temp varies brew temp. All about the temp patterns and trial and error. On my machine, if I get the routine wrong, the initial temp spike goes higher and the temp variation during the shot can blow out.

    To Q4 - You will have to work out the Temp patterns on your machine. Depending on your thermostat setting and how hot or not your Thermosyphon runs, the Brewing routine that best suits your needs wiil probably take a lot of observation and trial and error. At the end of the day, taste in the cup is the final indicator. Early on I had weeks where I was chasing my tail but eventually found what worked for me.
    Last edited by CafeLotta; 3 Weeks Ago at 01:32 PM. Reason: added Pressuestat is set too high comment
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  9. #59
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    Quote Originally Posted by CafeLotta View Post
    At the end of the day, taste in the cup is the final indicator. Early on I had weeks where I was chasing my tail but eventually found what worked for me.
    Amen to that.

    I drink milk coffees and found that the best taste for me and the coffee I use is to aim for 96C for the majority of the shot. Going for the 2-degrees under leaves me with a very "flat" taste.



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