danutco Senior Member Joined: 15 Dec 2012 Posts: 5 Location: Brasov, Romania Expertise: I like coffee
Posted Fri Dec 21, 2012, 12:59pm Subject: pump pressure reading: blind filter vs. extraction
it is about an E61 HX pourover machine (Bezzera Magica): after almost 4 months of a decent usage, and with the 9 bar OPV kit installed, I've found myself wondering if it is ok to have the same pressure indicated on the pump manometer while it reaches the top value during extraction, as it was when I've adjusted the OPV? meaning that I always extract at the OPV set pressure, even for normale shots; the 'POMPA" pressure gauge has its capillary connected directly to the pump output; there is a significant pressure drop, along the hydraulic circuitry from the pump output via pipes, HX, jicleur etc. up to the puck; so, for getting about 9 bar pressure on the puck surface, I have adjusted the OPV to open at 9.7 bar indicated on the pump gauge; and, unless I have a pronounced channeling, or I've... forgot to tamp, the pump gauge tops to the same 9.7 bar during the shot extraction;
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