High brew pressure on ISOMAC Zaffiro
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- Posts: 2
- Joined: 10 years ago
Hi everybody,
I'm a happy owner of an Isomac Zaffiro.
Recentely I noticed one thing about brew pressure, which has also been partially discussed here in the past; here is the thing: as many of you, when I pull a shot, I get pressures of approx 11 bars, which seems to be normal for this model.. the problem is that if I activate the pump without the portafilter (same thing happens if i remove the dispersion screen/gasket of the E61 group), so basically if I just run the pump without any apparent resistance, I get a pressure of 4 bars on the pressure gauge.
Does this happen to you too?
The problem is: if I have 4 bars of resistance just to get water to the portafilter, then (having the max pressure valve on the pump set to 11, for example) I'm left with "just" 11-4=7 bar of "real" pressure on the coffee, before the pump stars to send water back to the reservoir.
This might be the reason for which I always find my shot a bit sour, maybe I can't build the right pressure.
I've just descaled my machine, so everything should be clean.
Any ideas?
I'm a happy owner of an Isomac Zaffiro.
Recentely I noticed one thing about brew pressure, which has also been partially discussed here in the past; here is the thing: as many of you, when I pull a shot, I get pressures of approx 11 bars, which seems to be normal for this model.. the problem is that if I activate the pump without the portafilter (same thing happens if i remove the dispersion screen/gasket of the E61 group), so basically if I just run the pump without any apparent resistance, I get a pressure of 4 bars on the pressure gauge.
Does this happen to you too?
The problem is: if I have 4 bars of resistance just to get water to the portafilter, then (having the max pressure valve on the pump set to 11, for example) I'm left with "just" 11-4=7 bar of "real" pressure on the coffee, before the pump stars to send water back to the reservoir.
This might be the reason for which I always find my shot a bit sour, maybe I can't build the right pressure.
I've just descaled my machine, so everything should be clean.
Any ideas?
- erics
- Supporter ★
- Posts: 6302
- Joined: 19 years ago
The 3.50 to 4.00 pressure when simply flushing is due to the restriction imposed by the gicleur (~90%) and the summation of the other parts in the hydraulic system (~10%).
Adjust your OPV such that the gauge reads 9.0 bar with a blind filter and you will be in very good shape. You will then have a touch less than 9.0 bar presented to the properly ground and dosed coffee which is "just right". Your 11 - 4 = 7 bar is not correct but it would take a short thesis on fluid mechanics which I am not prepared to type.
Adjust your OPV such that the gauge reads 9.0 bar with a blind filter and you will be in very good shape. You will then have a touch less than 9.0 bar presented to the properly ground and dosed coffee which is "just right". Your 11 - 4 = 7 bar is not correct but it would take a short thesis on fluid mechanics which I am not prepared to type.
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- Posts: 2
- Joined: 10 years ago
I actually assumed it would have been more or less like a series circuit in an electric system.. but I read a bit about it and realized there are many other factors implied, thank you.
so you suggest to actually adjust the OPV to a lower pressure than 11 bar.. I'll try that.
so you suggest to actually adjust the OPV to a lower pressure than 11 bar.. I'll try that.