flaff Senior Member Joined: 20 Apr 2013 Posts: 1 Location: singapore Expertise: I love coffee
Posted Sun Apr 21, 2013, 3:19am Subject: Pressure issue on Bezzera BZ07
Hello, I've experienced some pressure issue with my BZ07 recently and am looking for advices. During extraction the pressure is not stable, moving from 7 to 9.5 bars every 2 seconds. I've descaled the machine but it doesn't solve the issue. Any idea about the source of the problem? Thanks.
Sounds like a pump related problem, or a gauge problem, or perhaps something is caught in the pipes. Try cleaning the inlet tubes, as well as checking the pump has no broken parts, with a commercial rotary pump, the pin can snap very easily if the pressure is adjusted when the water is not running throught the heads.
Quite a problem you've got there, but probably no big deal, might just need a new pump.
The pump on mine changes sound (and flow rate) as it operates when I pull, but on about a 10-15 second time scale - does this sound similar to your problem? I don't have a brew gauge so I can't check that. I haven't got to the bottom of this yet, but I'd suspect that either the boiler element is cycling on that time scale, and reducing the voltage at the pump, or the OPV or boiler fill valve is opening and closing as I pull a shot. The 3-way is definitely not the issue though.
I might be able to have a look at this later tonight, or in the morning.
I looked at this this morning on my machine. I get a change in pump sound, and a big increase in flow through the group, about 12 seconds into a pull (Flushed for ~11 seconds - 3-5 seconds after the end of the water dance). There's no flow through the OPV return at any point, suggesting that I'm not quite tight enough on the grind, but I don't think that affects things.
My next step will be to hook up a voltmeter to various points to see what's switching on or off at this point in a pull.
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