Thema: ES 90 Druckschwankungen

Bei mir siehts jetzt so aus, dass ich mit dem 2er Sieb und 20 sec Durchlaufzeit keinerlei Probleme habe. Wenn ich bei gleichem Mahlgrad das 1er Sieb verwende, verlängert sich ja die Durchlaufzeit und ich bekomme heftige Druckschwankungen. Beim Rückspülen gegen richtiges Blindsieb keine Schwankungen.
Wenn ich die Maschine jetzt einschicke, bekomme ich bestimmt die Antwort das es doch mit dem 2er Sieb problemlos klappt oder ich halt für das 1er Sieb gröber mahlen solle

Also bei meiner jetzt zweiten Maschine habe ich bei dem einfachen Zweiersieb auch Druckschwankungen.

Wenigstens kommt dann noch Espresso heraus, was mir bei dem doppelten Zweiersieb nicht mehr gelingt.
Ich geb´s bald auf.

Dirk

darf ich mal ganz doof fragen, was ein doppeltes und was ein einfaches Zweiersieb ist?

Ich nehme mal an dass er die normalen und die Crema Siebe meint

Seh ich das jetzt eigentlich richtig, dass jeder der einmal das Problem mit den Druckschwankungen hatte dieses auch nicht mehr behoben konnte?

Hi there,
Excuse me for writing in English, it's much easier for me, and believe me, also easier for you to understand than my German.

I've been fighting with my ES90 for the last three weeks, read a lot and experimented quite a bit.
At the beginning everything worked great. After an over extraction all went wrong.
I got all the pressure (low and fluctuating ) related problems as well as portafilter - collar leaking.

I have a theory that goes like this:
I see two valves (ventils, there may be more) the first one just after the water reservoir before the pump, so that the water won't return.
The second valve, after the pump and before the brewhead, sends the excess water from the brewhead to the discharge, stopping the water from returning to the pump.

Another important aspect is that (I believe) what actually commands the machine is the water flow sensor, the one that is programmable, that measures the volume of the shots and starts and stops the pump, nothing else.

I measured (several times) the water flow, by flushing, and my pump delivered an average of 275 ml/60 sec, half of what is reported for other machines in this forum.
Anyhow, as I still get more than the 25 ml in 20 - 25 secs needed for a shot, I still get excellent espressi, with pressure within the recommended manometer zone (about 11 to 12 o'clock).
However during the cleaning cycle, pressure only gets to 9 hs, therefore I believe that the pump delivers enough water for the espresso but not enough to build up pressure during the cleaning cycle.

Well, my theory is that the valve near the reservoir lets air get into the circuit therefore, having a mix of water and air, we'll have less water and consequently less water flow. Air compresses, therefore pressure fluctuations, and having a defective collar allows an additional pressure leakage through the gasket (Dichtung). Therefore while descaling won't actually do nothing (in a already clean machine) taking in and out the reservoir and rinsing without showers, may eliminate part of the air and tighten the connection, helping to fix the pressure problems.

Another point: forcing the backflush, while using blind filters and longer flushing periods (more than 10 secs as a guess), might force the second valve (as it only opens the discharge when the pump stops) till it eventually fails and allows a water return to the pump, with other consequences.

I don't know if it may also be the case, but I once actually damaged a garden water pump while functioning without water, only with air for a short time. It was useless afterwards.

I believe that avoiding air entering the system and implement a way of priming the pump could really help.

Cheers,

Bernardo

Oh ! BTW, the " relief valve" must be the blue silicon gasket. Another guess: a normal ST insertion (not overtightened) would mean about 9 bar, thight, goes to 11 or more.
Small black particles comming out of the steam wand ? Probably coffee grinds (from the ST, where else ?) that made their back way through the second valve, than backwards trough the pump (that can not be good for the pump) up to the first valve that redirected the grinds to the steam pump (also not good).

Measured the waterflow at my machine one year ago, was 380ml/min. Theoretically the pump should be able to transport 650ml/min at zero pressure (Maybe not when running in a machine). Will measure these days again. Also think the flow rate at around 10 bar goes already down to zero, pump-configuration in this machine seems a bit weak to me, since (in theory) 15bar are possible. If this weakness is due to air, dirt or valves in the system, because of purpose (to reduce brewpressure) or accident, no idea....

Aus den FAQs von Sunbeam/Australien:

How long should I allow the coffee extraction to go for
Coffee extraction should take somewhere from 6 to 10 seconds.
Applicable to all models: All

auch ne Möglichkeit, Druckschwankungen zu vermeiden



Sent from my eiFon using Tupperware

Zitat von knobelking

Seh ich das jetzt eigentlich richtig, dass jeder der einmal das Problem mit den Druckschwankungen hatte dieses auch nicht mehr behoben konnte?

Nee, ich hatte gelegentlich Druckschwankungen, die nach ausgiebiger Reinigung wieder verschwanden. Zur Zeit betreibe ich die ES90-2 seit ca 6 Wochen 5 Tage/ Woche auf der Arbeit und habe damit keine Probleme.