scanfield Senior Member Joined: 21 Nov 2011 Posts: 170 Location: Texas Expertise: I like coffee
Espresso: La Nuovo Era Cuadra Grinder: Baratza Vario
Posted Sun Sep 2, 2012, 9:23am Subject: Machine running cooler after a descale?
I have a La Nuova Era Cuadra and did my first descale yesterday. It took a long time and everything seemed to go well.
This morning, I let the machine heat up for longer than I usually do (90 minutes instead of 30) and when I went to do the cooling flush, only hot water came out the group head. Normally I get a lot of angry steam.
Would descaling affect the temperature the machine runs at?
I pulled a couple of shots, and dumped them down the sink. The third shot I drank and it was very, very good. Prior to descaling, I think my machine was always running too hot and I was planning on lowering the pstat. Now, it seems to be cooler. Are there any reasonable explanations for this?
Coffeenoobie Senior Member Joined: 11 Dec 2011 Posts: 2,320 Location: PNW Expertise: I like coffee
Espresso: N S Oscar Grinder: Vario W
Posted Sun Sep 2, 2012, 11:10am Subject: Re: Machine running cooler after a descale?
Guess: water flowing faster through the system? Heat exchange if the water is not moving it is over heating. That is why you need a longer cooling flush on an idle machine.
Coffeenoobie
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slybarman Senior Member Joined: 3 Nov 2011 Posts: 331 Location: usa Expertise: I love coffee
Espresso: La Nuova Era Cuadra Grinder: Baratza Vario
Posted Sun Sep 2, 2012, 6:59pm Subject: Re: Machine running cooler after a descale?
If you go back through the Cuadra thread you will see that I posted a similar result after descale where the group was idling a bit cooler than before the descale by maybe 4-5 degrees (I can't recall exactly now).
Posted Sun Sep 2, 2012, 9:01pm Subject: Re: Machine running cooler after a descale?
Without a grouphead thermometer (which I highly recommend for any E-61 group) it is difficult to know. I have a few ideas: - Remove the top cap off the group and check the gicleur and its screen for debris. - If the machine has a flow restrictor in the thermosyphon it may be partially clogged by scale. - Some scale is or was in the pressurestat and it is now operating differently. - A leak in the thermosyphon circuit (such as through the group) can cause a partial or complete thermosyphon stall. This will dramatically lower thermosyphon temperature and grouphead temperature. This leakage can be past a group seal, and the water can vaporize before an actual dripping can be seen.
slybarman Senior Member Joined: 3 Nov 2011 Posts: 331 Location: usa Expertise: I love coffee
Espresso: La Nuova Era Cuadra Grinder: Baratza Vario
Posted Mon Sep 3, 2012, 5:52am Subject: Re: Machine running cooler after a descale?
+1 for the grouphead thermometer. If you don't have one, you are just guessing at temps.
FWIW - Eric S was at my house shortly after I had done the descale and I mentioned the lower resting temps to him. He checked the gliceur, the screen and the grouphead generally. He did not find anything out of the ordinary and he really could not account for the lower resting temp. IIRC correctly it went from resting at 209 or so to resting at 204 or so.
The temp has remained stable, so I have not worried about it. I will see if it changes again when I descale next.
Every so often I will get a thermosyphon stall. With the group thermometer it is easy to identify and clear.
scanfield Senior Member Joined: 21 Nov 2011 Posts: 170 Location: Texas Expertise: I like coffee
Espresso: La Nuovo Era Cuadra Grinder: Baratza Vario
Posted Mon Sep 3, 2012, 5:59am Subject: Re: Machine running cooler after a descale?
It's actually at a much better temperature now. My cooling flushes are very quick and the result in the cup is improved as well. I don't know why the temperature is lower now, but I like it better.
For all E-61 group machine: Avoid short flushes UNLESS the shot will be pulled within a minute or so. A short flush can create a flash boil in the thermosyphon system. The resulting steam can settle in the upper thermosyphon tube and this can stop the convection within those tubes causing very low group temperatures. When normal group temperature at idle will be around 10 degrees lower than the boiler temperature, in a stall scenario in can drop to 40 degrees F. lower or more.
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