# Something funny going on here.. HX brew temperature/ pressurestat setting help!!



## Taff (May 5, 2015)

Been trying to find the cause of sour shots for a while now on my Magister setup. Got a lot worse when I switched to the SJ and its been doing my head in.

Had a huge session earlier this week where I went back to extraction basics and on purpose under and over extracted loads of shots to try and solve this. I also did a lot of shot pulling at different pressure settings to see the effect on taste. As you'd expect I ended up reducing my dose and increasing the shot weight (from 18.5>30g) to about 17/17/5>32/33 and found the sourness went.

On my pressure guage I found that I couldnt get acceptable shots with it switching the element off below 1.25 (about a .25 deadzone so back on again at about 1), more was better without it really tending to bitterness. I wasnt comfortable with running it at 1.5+ so left it at about 1.4 as was too caffinated to carry on, happy with the improvement.

Recognising that I was guessing without a temperature probe, I ordered on of these :

http://www.ebay.co.uk/itm/161391924900?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Pulled one of the best shots I ever have from the setup first thing this morning. Really pleased.. temp probe also arrived..

Having just been playing with it, I'm shocked!

calibrated it in boiling water (reads about a degree low)

Put my spouted portafilter in to measure water out of spout without basket in.. Machine been on for 3 hours or so. Ran machine for a minute or so. during that minute temp readout peaks at about 83 then eventually levels out at about 70!

Played about with pressurestat and thermometer.. (grouphead looks interesting - water cycles through brewhead then down to bottom of boiler with an M5 blanked takeoff directly above shower screen - e61 ish?)

The best I can get is (and Ive just checked this after leaving machine idling for ~10mins) this is no flush and after 10 mins idle - initially water is 93, then creeps up to 94 degrees. after about 10s it drops slowly (about a degree a second) to 75 degrees and levels out there. Results are broadly the same if about 3 degrees hotter if I use the bare thermocouple lead ends on the inlet tube to the grouphead that comes with the thermometer, rather than the immersion probe in the PF outlet. Sputtering from PF for 5-10 secs

This is with the pressure guage peaking at 1.8bar!!!!! any higher and the safety valve starts to cuts in..

Shots taste OK, if a little flat - but not sour (or overly bitter).

Whats going on?! What to try next? Either pressure guage is faulty and/ or the safety valve is cutting in low.. or my measuring is waaaaay off, or i've now got it about right - but to my mind it should eventually level out at about 90, and the pstat should be about .6bar lower?!

cheers for your thoughts!

James


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## espressotechno (Apr 11, 2011)

Your steam pressure is far too high. The higher the steam pressure, the higher the HX water temperature, and the more acidic & "burnt" the brew.

The lower the steam pressure, the sweeter / smoother the brew will be.

The optimum sream pressure for your Magister is 1.0-1.1bar.

You can safely drop to 0.9 or even 0.8 bar without losing too much steam output.

PS The Magister grouphead is a Rancilio clone, as are a lot of other Magister parts (useful when ordering spares....)


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## Taff (May 5, 2015)

^^ thanks. That was what I had set it to (new pressurestat a few months back) and I was getting way too low brew temps and very sour, tart coffee (less than 85 after idling and no flushing!) I guess I need to change the pressure gauge as a first off then see where I am.


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## Taff (May 5, 2015)

Ok.. think I'm getting to the bottom of this one. I've now araldited the thermocouple to the place I think gives me the best indication of water temp - the copper tube just before it goes into the grouphead.

This has given much better results that are much more similar to those Ive seen in various HX threads.

Seems the rule to learn was an old one. Each HX machine has its idiosyncracies, and they have to be learnt. The length of the cooling flush are individual to each machine and its pstat setting and you cant tell without a temp gauge and some taste buds.

I have some way to go but now have a much better idea of what length flush to do and what the machine is doing. I prefer it on the hotter side, but the pstat is not down cycling between 1.1 and 1.3 and I could brew at 98 if I wanted to!

Obligatory setup shot.


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## Dylan (Dec 5, 2011)

Where you have your probe may not be the best place. A large amount of temp stability comes from the group itself, a principle that most machines use. After the water exits the HX tubing it passes through a very thin tube within the group, and the brass around this levels the temperature of the water. Water in the HX tube could be both too hot or too cold, but the group helps to level this before it hits the puck.

Using that very same probe I have found the best place to get readings on an e61 is to remove the shower screen and dispersion plate, at which point you can see the exit hole for the water, if you poke your probe up this hole you will get a very good reading of what temperature the water is at as it is exiting the group.

You will however get differences in temperature at nearly every point, the one that is most important of course is the point at which the water hits the coffee bed.


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## Thecatlinux (Mar 10, 2014)

This may demystify a few things

https://groups.google.com/forum/m/#!topic/alt.coffee/afpVV5xUCc4

i can only take credit for posting the link


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## Taff (May 5, 2015)

Thanks for that guys.. ideally I want to do something with the m5 hex in the back of the brew head.. meanwhile, have change my thermocouple location to the back of the grouphead on the water pathway to the showerscreen.

Hadnt thought through how a thermosyphon really works! All I was doing was measuring that temperature. Much appreciated.


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## Dylan (Dec 5, 2011)

Taff said:


> Thanks for that guys.. ideally I want to do something with the m5 hex in the back of the brew head.. meanwhile, have change my thermocouple location to the back of the grouphead on the water pathway to the showerscreen.
> 
> Hadnt thought through how a thermosyphon really works! All I was doing was measuring that temperature. Much appreciated.


I think that the grouphead is actually a good point to read the temp from, the group should be at the right temperature in order to stabilise the water temp. You can only know if its doing its job however by reading the internal water temp.

If you haven't already then look up and do some reading on 'Eric's E61 thermometer'


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## Taff (May 5, 2015)

Thanks, yeah I've done a lot of reading of the erics threads. Tempted to drill a hole in the bolt in the grouphead and epoxy the other thermocouple probe into it.

Just done a few hours of testing of the new location, much better thanks for the idea lads. I think i was on the right track initially - the machine does run cold so I guess the pressure guage is off. with Pstat peaking at 1.3 the grouphead doesnt get above 85 at idle. have tweaked it and it sits at 94 ish. A 10 sec flush (sputtering ends - it never used to sputter before, however long it had been left idling - another 'coldd' indicator!) sees the temp peak at about 97 then drop back to a brewing temperature. temperature then stays constant to within a degree for the course of a shot.. which tastes great.

Progress in leaps and bounds! A DB machine is getting even more attractive by the minute though lol


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## Taff (May 5, 2015)

Big thanks to all who commented. Shot pulling has now definitely moved a level or two up. Can't stop drinking them today! No sourness, sweet and I can taste things that are a bit like the roasters tasting notes! More - consistency is there. Happy camper.


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