A guide to managing HX brew temperatures - Page 3

Beginner and pro baristas share tips and tricks.

#21: Post by HedonisticBeans »

I have a rocket appartamento

I've always wanted to know group head idle temperature and flow extraction temperature

I picked up a Chris' coffee (Eric's?) thermometer

My machine idle temp is 89 Celsius

It peaks to about 94 Celsius when extracting then drops down to about 92.

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#22: Post by Bluenoser »

When you are looking at the group head thermometer, the spike at the beginning is very characteristic of all HX machines as the water at the top of the thermosiphon is at its hottest .. , but the E61 acts as a large "heat sink" and evens out those huge differences in water temps of the water flowing through it.. So your puck doesn't feel that high temp spike.. (usually that spike might go up 4C degrees on some machines).. There also will be a drop from the group thermometer to the puck.. so at the end of your shot, is your group thermometer reads 92, the actual brew water temp might be 90C.. This is because of the drop in temp as it travels through the group to the screen.. On my HX, the idle temp ends up being almost exactly the same as what the brew water will be, assuming the group is warmed up.

If you do a flush and then immediately pull, then the above is not true.. (there are 2 types of flush.. a flush-n-wait and a flush-n-go.. you can research on HB). The above is true when the group is cooler than the water in the thermosiphon, which is when you use no flush.. or you flush, wait for the temp on group to bottom out (about 1-3 minutes) and the temp starts to climb again.

You can borrow a SCACE to see the relationship on your workflow to the temp on the thermometer and the actual brew water temp or you can mount a thermocouple on the bottom of your screen as many have done. Once you do this, you will be able to characterize your machine and will only need the group thermometer.

On HX's with slow rebound, the group thermometer is necessary to tell when your thermosiphon water has reheated enough to pull successive shots.. The Appartamento is fairly quick with a 3mm restrictor in the TS.. My Profitec 500 is very slow (5-15 minutes, with a 2.5mm restrictor)
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Howardsmith (original poster)

#23: Post by Howardsmith (original poster) »

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

Howardsmith (original poster)

#24: Post by Howardsmith (original poster) »

Rakan wrote: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?
My previous post above was a reply to this post quoted here.

Howardsmith (original poster)

#25: Post by Howardsmith (original poster) »

yonika wrote: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 :)

The temperature sensor is on the base of the e61. Please ignore any thermometer readings in those photos. They were just for demonstration.


#26: Post by cortaydo_cortado »

Hi Howard,

Great work! I have a Quick Mill Andreja Premium E61 HX machine that is new to me. I've found your work the most useful in my search for controlling brew temp on this machine. I'm currently playing with adding a Raspberry Pi 4 to act as a PID for me.

The machine currently has a pressurestat wired to the SSR. I am looking at where and how I should wire the PID in - parallel to the p-stat, after it, etc. Could you share some details on how you wired your PID?