Bezzera Strega boiler refill

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#1: Post by Leverer »


I'm a happy Strega owner for over 5 years by now. 3 espressos a day without any issues so far. For sometime I have noticed though that when I turn the machine on I don't hear the pump filling the boiler. Also when I let some hot water into a jug (for testing purposes only) I don't hear the pump engaging. I have just replaced the Ulka pump for some other reason (it started to stop working at the end of a shot) but the boiler (no)refill issue still persists. The boiler pressure is around 1.3 bar. As I only drink espresso I don't really care for how much water there is in the boiler but I don't want to ruin my machine that still produces excellent shots. Do I have a problem? Where should I start the diagnosis?



#2: Post by jpaulm »

I am not a technical person, but a couple of questions come to mind: If you have used the machine for 5 years, the behaviour you are noticing must mean there has been a change. Does it coincide with the replacement of the Ulka pump? Could there be a wire or connection missed when you replaced it? I wonder what would happen if you drained the boiler completely - would it re-fill then? Finally, is there a low water sensor that would prevent damage to your machine? Maybe someone with more knowledge and experience will jump in.

Leverer (original poster)

#3: Post by Leverer (original poster) »

Thanks for taking the time to respond.
I have just recently replaced the pump long after I noticed that the boiler refill sound is missing when I switch on the machine.
Draining the boiler is a valid idea, I'm worried though that it might overheat. Theoretically there is a low water sensor in the Strega but I have no idea how to test its integrity.

Leverer (original poster)

#4: Post by Leverer (original poster) »

I dared to drain the boiler, by first heating it up until the pressure reached 1 bar then I switched it off and opened the hot water tap. When I turned the machine on again the pump started immediately without the heating indicator being lit for some time. Then the heating lamp turned on and soon the boiler reached 1.3 bar. This, I think indicates that all features - safety features included - are working correctly. So it seems that my Strega is just fine.



#5: Post by Marmot »

It sounds like your Strega is working fine again.
It is not a bad idea to exchange the water in the boiler from time to time. I got very soft water and emptied the boiler to fill it up with this soft water. When you have harder water in the boiler it tends to accumulate limestone faster.

You wrote that you changed the pump because it stopped working at the end of a shot. How do you pull a shot on your Strega?
Usually you pull down the lever and the pump works until you let go of the lever a little (for preinfusion) or lift it all the way so the spring can start extracting.

Leverer (original poster)

#6: Post by Leverer (original poster) »

This is how I pull a shot (based on instructions on this Forum I have installed a pressure gauge that measures the group head pressure): I pull the lever until the group head pressure rises to 5 bar. At this point I disengage the pump by lifting the lever slightly and wait until the first drops of coffee appear, then reengage the pump until the pressure reaches 12 bar which is equal to the the spring pressure. I release the lever at this point and enjoy coffee. Summary: 5 bar pre-infusion, 12 bar extraction.


#7: Post by Marmot »

Ok, that sounds right, albeit with relatively high pressures. I usually go for 1,5 bar preinfusion and let the pump run to about 3 bars which probably gives a peak pressure of 7 to 9 bars.
I just wondered because you wrote that the pump shut off at the end of a shot. You mean it did not go up to 12 bars in your case?

Leverer (original poster)

#8: Post by Leverer (original poster) »

Yes, the pump noise turned from buzzing into almost silent vibration and the flow almost stopped at the end of the shot. But that's the past! In my experience on the Strega the initial piston pressure is always 12 bars as this is the spring pressure.