Just bought a new Vibiemme and having a lot of fun experimenting. I’m going through coffee like it’s going out of style. I noticed the brew pressure was up around 13 bar. The manual states that the pump pressure should be 9 bar ±1 bar. Later it talks of an optimum brew pressure of 8.6 to 9.2 bar. Anyway, it seemed to me that one was supposed to adjust the grind and tamp to achieve that brew pressure. Try as I may I couldn’t do it. The brews were either bitter or sour. The next step was to attack the pressure relieving valve (PRV). It took about ¾ of a turn to get the brew pressure to around 9 bar. There was a better balance between bitter and sour and neither was too distinctive. Did I do the right thing? Has anyone experimented with this? It seems incongruous to me that they recommend 9 bar then supply the machine with the PRV set to 13 bar. I’ve since read that it’s not unusual for machines to be delivered with the PRV turned right up. I’ve also read that there might be about 1 bar head loss in the system so it might be better to set the PRV to 10 bar. With the large diameter plumbing and the low flow rates, I wouldn’t have thought the losses to be that high. What do people think? Does it matter much anyway?
Another thing, in drawing a brew, do people hesitate half way to get the pre-infusion? If so, how long? The manual makes no mention of it.
By the way, where do these guys get their manual writers from? They wouldn’t pass junior high English here. Work this out, “When coffee starts going out from handled, look at pressure gauge, the perfect diffusion screen is when the pressure gauge indicates between 8,6/9,2 bar. If the value is higher it means that coffee is too dense while if it is lower means coffee has been ground too much thin.”
Another thing, in drawing a brew, do people hesitate half way to get the pre-infusion? If so, how long? The manual makes no mention of it.
By the way, where do these guys get their manual writers from? They wouldn’t pass junior high English here. Work this out, “When coffee starts going out from handled, look at pressure gauge, the perfect diffusion screen is when the pressure gauge indicates between 8,6/9,2 bar. If the value is higher it means that coffee is too dense while if it is lower means coffee has been ground too much thin.”


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