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I have already shared all the same info over there too mate.
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A guide to managing HX brew temps
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Hello Howard, thank you for laying out that guide & for the comprehensive documentation. It's been fun following along & implementing your method. I got my machine, the Mara (not X) a short while back. As much as I would have loved to get the X, it just wasn't a possibility.
The one thing I was most concerned about, before comitting to an HX, was temprature management. Given that I don't have a group head thermometer & no means of aquiring one either, I assumed temprature to be a black box for me. The idea of flushing, & potentially wasting much water everyday just didn't appeal. Then I found your post on HB, and suddenly, there was a ray of hope! Soon as I got the machine, I sourced that parts and this is where I'm at today -
![Engineering Gas Machine Electric blue Auto part]()
And this is it's (second) brain -
![Circuit component Electrical wiring Electronic engineering Computer hardware Gas]()
Ever since I started reading up on modding the Gaggia Classic, I was fascinated with Arduino & the whole DIY electronics ecosystem. Sadly, the Gaggia never graced our lives. But then, little Mara came along & I found your post & finally, I had the oppurtunity to dabble with Arduino! There's a k-type thermocouple taped to the chopstick, that slides in behind the group. The fan is hooked onto the relay. It turns on once the temp crosses the pre-set hight & goes off once there's a dip below the low. It's not the neatest setup, but I'm still learning.
I'm very new to espresso, there's a lot I don't yet know. But I'm able to clearly discern the difference in flavour at different tempratures. I've been trying out different coffees, at different roast levels and the temprature control has made it possible to pull shots optimally. Best of all, no cooling flushes necessary, no water wasted!
As much as I've been learning & enjoying the whole process, there's a lot I don't know. The thermocouple reading is all I have to gauge the group temp, with no way of knowing what's happening at the puck. Before, I was using a cooking thermometer to check the temp -
![Motor vehicle Crankset Automotive lighting Automotive tire Bicycle tire]()
Don't know about it's accuracy, but this thermometer would settle at around 93 C after warmup. The thermocouple settles at about 100 C. This doesn't make sense, 100 would be too hot, but the shots don't come out burnt. I have no Idea of how a reading of 100 C taken from behind the group, would corelate to the reading of a group head thermometer. My temprature reading before & during extraction remains almost constant, since the thermocouple isn't coming in contact with water, unlike a grouphead thermometer.
I've seen that in your automated setup, you've stuck the thermocouple behind the group too. Could you shed some light on this mystery?
You mentioned in the first post that you have another approach to this whole thing in mind. How's that coming along? I'll be tuned in to know more about it.
The one thing I was most concerned about, before comitting to an HX, was temprature management. Given that I don't have a group head thermometer & no means of aquiring one either, I assumed temprature to be a black box for me. The idea of flushing, & potentially wasting much water everyday just didn't appeal. Then I found your post on HB, and suddenly, there was a ray of hope! Soon as I got the machine, I sourced that parts and this is where I'm at today -
And this is it's (second) brain -
Ever since I started reading up on modding the Gaggia Classic, I was fascinated with Arduino & the whole DIY electronics ecosystem. Sadly, the Gaggia never graced our lives. But then, little Mara came along & I found your post & finally, I had the oppurtunity to dabble with Arduino! There's a k-type thermocouple taped to the chopstick, that slides in behind the group. The fan is hooked onto the relay. It turns on once the temp crosses the pre-set hight & goes off once there's a dip below the low. It's not the neatest setup, but I'm still learning.
I'm very new to espresso, there's a lot I don't yet know. But I'm able to clearly discern the difference in flavour at different tempratures. I've been trying out different coffees, at different roast levels and the temprature control has made it possible to pull shots optimally. Best of all, no cooling flushes necessary, no water wasted!
As much as I've been learning & enjoying the whole process, there's a lot I don't know. The thermocouple reading is all I have to gauge the group temp, with no way of knowing what's happening at the puck. Before, I was using a cooking thermometer to check the temp -
Don't know about it's accuracy, but this thermometer would settle at around 93 C after warmup. The thermocouple settles at about 100 C. This doesn't make sense, 100 would be too hot, but the shots don't come out burnt. I have no Idea of how a reading of 100 C taken from behind the group, would corelate to the reading of a group head thermometer. My temprature reading before & during extraction remains almost constant, since the thermocouple isn't coming in contact with water, unlike a grouphead thermometer.
I've seen that in your automated setup, you've stuck the thermocouple behind the group too. Could you shed some light on this mystery?
You mentioned in the first post that you have another approach to this whole thing in mind. How's that coming along? I'll be tuned in to know more about it.
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I'm glad you have found the info useful and are using it effectively.
Firstly your 100c temp behind the group may be correct, most likely. Temp varies in different locations on the GH. The top of the group is much hotter than the lower end because the thermosyphon only really circulates through the top section.
My findings were that with my machine brew water temp would be around 2.5c above the temp displayed on my GH thermometer prior to initiating the shot. With my automated set up with the thermocouple fixed to the flat section on the underside of the e61 where it attaches to the machine the temp displayed almost matched my GH thermometer. I think I needed to program a small offset, maybe 0.5c for it to match up.
Numbers really do not matter if you can distinguish differences in taste at different settings. I can nail whatever temp I want now consistently without flushing but really knowing what temp it is at is irrelevant, I simply dial in to around a roasters recipe at 93c and then play with pushing the temp up and down 2c each way. This could be as simple as saying 'let's try a hotter shot, or let's try a cooler shot'.
My initial goal was to come away with the ability to produce a 'hot' 'medium' and 'cool' shot. It turns out that the fan method is so reliable that we can realistically reproduce almost identical shots, shot after shot at any temp we like by simply managing the GH temp.
I'm currently not using the automated set up because the relay/fan kicking in and out kind of drives me nuts. I simply fan down with the small fan and pull the shot on the rebound. Good luck with your set up, it certainly looks more complex than mine and looks like you have had a bit of fun tinkering, which IMO is what it's all about so keep it up.
As for the other automated method.... Temperature controlled solenoid valve in the thermocouple to completely bypass the e61 once temp is achieved. Some kind of override controll via the pump switch.
Not done it yet, may not do it but that's how u would automate this in a more professional way.
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This approach seems so much simpler than, as you mentioned, the Mara X way. There would be some kinks to iron out along the way, I suppose.
One thing that comes to mind, if the thermosyphon bypasses the E61, water in the HX might tend to superheat much, much faster, without dissipating heat to the group. This might need additional management.
It would be so much fun if some sort of temprature management modding kit for HX machines existed, much like what MrShades has done for the Gaggia Classic. This is an oppurtunity I've missed out on by not getting a GC, getting deep inside a machine's guts and tinkering around.
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Definitely.
I am not a 'super taster' and drink all my shots in milk. I can clearly taste a difference even in a milk drink when the temp it too hot or too cool.
For a long time I was running my shots way too hot and not getting what I wanted. My shots are now way more consistent.
What machine do you have?
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This sounds interesting, so the hx is almost behaving like a thermocoil where brew water heating is only happening at brew time?
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It's worth bearing in mind that the Xenia design is very different to the standard e61 HX machine with thermosyphon.
Look at this diagram. My understanding is that the group is also actively heated with PID controlled cartridge heaters.
Draining the HX on an e61 HX machine after each shot would not produce the same results that the Xenia achieves.
But you are correct, if you look at the diagram you can see the relatively small capacity HX which coils through the steam boiler. I think once the solenoid opens post shot, gravity will simply drain the path. The only issue I can see with this would be the potential for an introduction of steam at the beginning of a shot since the brew path (hx pipe) will be empty of water and likley full of superheated air/steam. In reality this may not cause an issue and may not even happen, I don't know the ins and outs of the machine.
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Thanks Howard, very interesting machine - group head heating adds another level of sophistication
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It does... check this out from the coffee machinist on Instagram...
He fitted two cartridge heaters to this ECM machine and I think it boasts an 8 min warm up time.... The heaters are PID controlled, you can see the thermocouple, drilled and tapped in the centre I'd assume. This is the same location as my thermocouple although mine is simply surface mounted with heat sync glue.
I have considered it, but I'd like to find an old knackered e61 HX machine instead of machining holes in mine TBH. If I ever come across one it would make a great project.
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Most enjoyable thread thank you
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I think the way the group is being heated is through what they're calling a 'Thermal Bridge', where the boiler is thermally connected to the group.
As mentioned on this page - https://xenia.coffee/thermische-eignung/.
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Howard, thank you for this great work, and sharing it with us.
Been doing your fan method for a couple of days.
I'd like to ask, why do I not experience the temperature hump?
extraction starts @88.5c "rebound", and the sensor shows exactly 90.3c constant.
Seriously, 90.3c constant till the end of the shot, did not fluctuate, and no hump, just constant.
I got Appartamento factory set @1 Bar
with E61 sensor by "coffee sensor (black version)"
The numbers I'm getting are ridiculously constant.
for example, rebound @89.5c it hits 91.6c constant till the end of the shot.
Am I missing something, or these are an actual real readings?
Been doing your fan method for a couple of days.
I'd like to ask, why do I not experience the temperature hump?
extraction starts @88.5c "rebound", and the sensor shows exactly 90.3c constant.
Seriously, 90.3c constant till the end of the shot, did not fluctuate, and no hump, just constant.
I got Appartamento factory set @1 Bar
with E61 sensor by "coffee sensor (black version)"
The numbers I'm getting are ridiculously constant.
for example, rebound @89.5c it hits 91.6c constant till the end of the shot.
Am I missing something, or these are an actual real readings?
It's a "Duplicate post"
Follow up,
I got a temperature sensor on the basket with 17.5g of coffee
GH stand by temperature 96.5c, fan method cool down. No flush before or after extraction. Zero flush.
Started the extraction doing the same numbers which is 89.5c rebound.
Temperature in GH sensor is 91.7c constant with zero fluctuation!
and temperature on the puck is 91c, with extraction time from the start 40 seconds.
Puck temperature was solid 91 with 2 fluctuations, first one @10 seconds of extraction for 5 second to 92c then back to 91c
, and second one was at the end of extraction for 2 second to 90c, and then back to 91c
beside that, the entire extraction was spot on 91c.
Bare in mind, the puck sensor is thick, and it was leaking a bit, nothing major, and maybe it was the reason of the puck sensor fluctuating.
yet, GH sensor did not fluctuate it was 91.7c constant.
Truly, those numbers are amazing. I did this method 7 times, and all were spot on constant Temp numbers.
Mr. Howard, what do you think about these Temp readings, and should I change something in my routine?
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Really late reply, not been here for ages...
Your results are almost exactly what I would expect based on my own testing. Your machine being set to 1 bar enables it to brew a 'flatter' profile at 91c because the initial rush of water at the start of the shot it cooler in comparison to say water from a 1.3 bar boiler. The HX hump is affected by the HX water temp, average brew temp is determined by group head temp with this method.
If you're happy at 1 bar keep it there. You will get flatter temperature profiles, but you will also have less steam power & slower recovery times. Set the boiler pressure based on your routine really.
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