A guide to managing HX brew temperatures - Page 2

Beginner and pro baristas share tips and tricks for making espresso.
Howardsmith (original poster)

#11: Post by Howardsmith (original poster) »

Bluenoser wrote:Current HX manufacturers need to re-think their design in an era where people are increasingly concerned with fine tuning the brew water temperature to adapt to lighter roasts; and to address the interest in flow profiling. They should cease the claim that a PID on the steam boiler will create an absolute and stable brew water. It won't. And instead, increase their education on how to get the best brew water control from the HX design. Certainly the MaraX is Lelit's attempt to address these issues with the HX design.

Having a temp Monitor for water inside the group, or at the screen allows a user to develop a useful workflow AND gives the user confidence on the absolute value of the brew water without having to invest significant additional cost on a group thermometer. It can also let you know if you've pulled back-to-back shots too quickly and your brew water has not reheated sufficiently.

Having a pressure gauge on the front measure the actual pressure in the group would not only help standard extractions, but would allow use of the E61 Flow mod without needing another pressure gauge. This keeps the aesthetics and makes the mod cheaper.

Throw in a bottomless PF instead of the single-spouted and you'd have an HX machine that would provide a significantly easier learning experience for those entering the espresso hobby.

Great work above to characterize the Rocket HX. And really great idea in looking at alternate ways to manage the brew water. I took that idea and now use a cold dish rag that I throw on my group If I notice it is above 201F. Instead of flushing, this brings my temp down to 195F, at which point I remove the rag, prep and pull. Waaayy easier than flushing and waiting ... and certainly saves on water.
We have already discussed this via PM Dave but it it worth keeping the ball rolling here too.

As you say current manufacturers are quite happy to 'keep it traditional'. I think they think people are happy to buy the machines because 'the e61 has stood the test of time'.... sure the e61 is a great piece of mechanical engineering and one of its 'best features' is that it weighs around 4kg giving it a massive thermal mass. The only problem being if machine manufacturers can't (can't be bothered) to optimise the machine to idle at the correct temp then all that thermal mass is working against you.

I'd imagine in a busy Italian bar where espresso is being banged ten to the dozen on quick succession the group would probably idle 'about right'.

I have automated my process now... I will share soon but the Fan/PID set up enables me to walk up to my machine and pull a shot at whatever temp I have programmed. I think if I can knock this up in my kitchen with bits from ebay these big manufacturers should probably be a bit ahead.

I know you're using that wet rag Dave but I'm going to be encouraging you to get a small battery fan and experiment with a hotter machine and the ability to hit different temps with ease and quicker rebound times.


#12: Post by untoldex »

Great measurements and observations.

I'm just wondering about water temperature in HX circuit. If we just control GH temperature by blowing with fan, does it mean that HX water temperature doesn't have impact on final brew temperature on the puck? Or it has such small impact that can be ignored?

I thought that with Erics thermometer, we check GH idle temperature, but then with flushing we can control HX water temperature (by stopping flush in certain moment).

How then "fan method" will behave in scenarios below:
1) Machine idle for 1 hour. Water in HX is super-heated, probably around 120C.
Initial GH temp is 97C, we blow with fan, and bring GH to 93, then pull a shot.
2) Machine idle for 5 minutes. Water in HX is not-so-super-heated, probably below 120C.
Initial GH temp is 94C, we blow with fan, and bring GH to 93, then pull a shot.

What you are saying (based on your observations) that in both cases we will get target temperature 95C?

Howardsmith (original poster)

#13: Post by Howardsmith (original poster) »

If you look at the 1.1 bar results and compare shot 1,4 and 5 I have done exactly what you are saying...

Shot 1 was pulled after a long idle

Shot 4 was pulled after a 12 min recovery after a much cooler shot

Shot 5 was pulled 4:20 after shot 4

All 3 shots settled in to a stable temp of within 0.2°C of each other. After a longer idle you will get a higher hump at the beginning, this can be seen in the graphs. This hump can be reduced by including a screen flush before the shot is initiated. I show

Read and reread the info, also watch the video, after doing so you should have your head around the theory.

As far as flush and go we have two variables at play. When we flush we are introducing cool water into the HX but we are also cooling the group. Both variables come into play and this is what makes the method a little more tricky.


#14: Post by untoldex »

Thanks for clarification!
So then it means that when using "fan method" we can just measure grouphead temperature with simple thermocouple sticked to E61 neck (the hottest part). It should show higher temperature, much closer to one that we target.
Thanks to this we are able to mount flow control pressure gauge on the front of the group :)

Howardsmith (original poster)

#15: Post by Howardsmith (original poster) replying to untoldex »

If you wish to install a flow control device I would recommend mounting some kind of thermocouple to the underside of the e61 near where it meets the casing. If you wish for the cabling to be concealed in the casing you may need to remove the e61, take a small section out of the fibrous gasket that is sandwiched between the e61 and the casing and route the cabling through that gap. Thermal glue can be used to mount and then a layer of foil tape to conceal the thermocouple. You would never know it was there.

Play around with finding a location where the readout on your GH thermometer matches the new thermometer. The GH thermometer can then be removed and the FCD installed.

Howardsmith (original poster)

#16: Post by Howardsmith (original poster) »

Here is a video of my automated set up. This maintains my at puck temp usually to around 0.2°C so long as I give the group time to stabilise.... When quickly changing between settings on the PID the new temp needs some time to 'settle in' before the at puck temp is consistent.

Had it set at 91°C this morning, walked up, prepped shot, screen flushed and got 90.1°C.... not bad.

Howardsmith (original poster)

#17: Post by Howardsmith (original poster) »

Here is the automated set up now with wiring concealed.

I did plan to put the fan on the underside and use copper piping to route the air to the group... Maybe a future mod.

Not the best looking thing but some people have an ACS Minima on their counter top so in comparison this isn't too bad :lol:


#18: Post by Rakan »

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?


#19: Post by yonika »

Howardsmith wrote:Here is the automated set up now with wiring concealed.

I did plan to put the fan on the underside and use copper piping to route the air to the group... Maybe a future mod.

Not the best looking thing but some people have an ACS Minima on their counter top so in comparison this isn't too bad :lol:



Merry Christmas!!

Great concept,

The only two things I'm not sure about and would love to understand :
1. Where is the PID measuring the temp on your setup?
You set the PID to 93 but the puck thermometer it shows 75C at idle.

2. Because the thermometer is idling at 75C or so, how is it able to record the hump? Until it reaches 90+ Temps, the temperature should settle on the flat portion of the graph.

Hope you're still visiting the forum to answer these questions :)



#20: Post by maltur »

Thanks for all the work you've put into this idea. It inspire me to give it a go; and I must say my fan is now a permanent fixture I love it.
Here's my implementation. http://www.youtube.com/watch?v=8vVexTZHG1o