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Bianca group head pressure


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Hi. I am a total newbie who has purchased a Bianca recently (upgrade from a bean to cup machine). I have been watching vids playing around with the machine and have a question that I cannot seem to find the answer to.

So i have checked and the pump pressure seems to be set to 10bar. However when I put in a blind filter the pressure on the group head gauge is over 11. I would have thought that these 2 should be the same with the blind filter fitted? And does it really make a difference if I can close the paddle to 9ish when brewing?

This is a steep learning curve for me. 

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I think it should, but I might be wrong. @DavecUK knows the machine very well so maybe he knows why. If it should, then it might be the gauge at the group is not calibrated the same as the gauge on the machine. Moreover, you could do a simple test: adjust the pressure on the pump to 9 bar. What does he pressure in the group read? 10 bar?

Current: Lelit Elizabeth / Niche Zero / VST baskets / Distilled water + 100mg NaCO3/L

Previous: Gaggia Classic | Eureka Mignon | Rocket Cellini Evo | Profitec 700 | Profitec T-64 | Gene Cafe CBR-101 | Kinu M68 | Feldgrind 2 | La Pavoni Europiccola 2012

Also at: CoffeeTime Forum & Niche Zero Owners Group

 

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Water entering the boiler expands on heating, the rotary pump pumps into a system via a 1 way valve. With a blind portafilter, the system is sealed and that small amount of room temperature water entering this sealed system, as the blind filter fills, is enough to raise the pressure to 11 bar or even higher when it heats..

 

You may notice it will initially go to 10, or whatever the pump is set to, seem to pause for a moment then start rising to 11+, as the water heats up.

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Nothing here...

 

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If just checked and the needle starts of slow. Then just goes straight to over 11. But the pump is still at 10. I'm really confused. As when making coffee with the paddle fully open and I've grinder correctly the gauge pressure will still go to 11 and I will close it to get it to 9.

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14 minutes ago, Joy87 said:

If just checked and the needle starts of slow. Then just goes straight to over 11. But the pump is still at 10. I'm really confused. As when making coffee with the paddle fully open and I've grinder correctly the gauge pressure will still go to 11 and I will close it to get it to 9.

Dave provided a very good rational explanation. The missing bit for me was the one way valve and the water heating up, something I often forget 🤦‍♂️.

don’t pay attention to the gauge on the machine. Use he manometer at the group and take that as the de facto reading. 

Current: Lelit Elizabeth / Niche Zero / VST baskets / Distilled water + 100mg NaCO3/L

Previous: Gaggia Classic | Eureka Mignon | Rocket Cellini Evo | Profitec 700 | Profitec T-64 | Gene Cafe CBR-101 | Kinu M68 | Feldgrind 2 | La Pavoni Europiccola 2012

Also at: CoffeeTime Forum & Niche Zero Owners Group

 

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Try not to overthink what your doing. . 

You dont  have to hit 10 bar at the PF to maker good coffee it can be less and out can decline as the shot progresses . Ive had great coffee at 4 bar at the PF for example 

You are flow profiling not pressure profiling , so dont get hung up on the pressure at the PF it is rare for example i ever open my adddle all the way anymore, 

I tend to start off with it at 6oclock and see if the dose grind will get me to 8 plus bar at the pf , and go from there .

You

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Yes I think i am totally over thinking it. Been changing the grind etc.. and the coffee has been awful. Guess it allows for greater variation if required. Will continue learning and see how I go I guess. Thanks

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