Topic
Hydraulics and thermal control
What the machine delivers to the basket, and where it differs from what the gauge reports.
Scope
Pumps, over-pressure valves, group hydraulics, restrictions and their pressure drops, preinfusion, flow profiling, and the thermal behaviour of boilers and groups during and between shots.
Articles (5)
PID 120°C is not one brew temperature in these HX manuals
Shows that two heat-exchanger manufacturer manuals examined here attach different brew/outlet figures to the same PID-displayed boiler temperature of 120°C — Makina about 91°C outlet at about 1.2 bar; Rocket Giotto/Mozzafiato 93.6°C Scace…
Coffee-boiler 95°C is not the 97°C warning or the 93.8°C display
Shows that La Marzocco Strada AV and Linea PB operating manuals examined here attach three different coffee-boiler temperature kinds of claim that do not coincide: Strada’s parts description prints an adjustable operating temperature of…
Fifteen bar on the Ulka E5 curve is zero flow
Reads CEME/Ulka’s Family E high-pressure flow table — where model E5 shows 0 cc/min average flow at 15 bar — against machine documents that list “Pump pressure 15 bar,” and against De’Longhi EM450M copy that pairs a 15-bar pump figure with…
What pressure actually reaches the coffee
Separates the documented fact that nine bar became the convention from the undocumented engineering claim that Gaggia's lever spring produced it; distinguishes the three pressures the figure is applied to; traces the familiar 1.5 bar…
124°C at 1.25 bar is not the same steam-boiler pair as 120°C at 1.2 bar
Sets manufacturer steam/service-boiler pairings examined here of PID-displayed temperature with boiler-gauge pressure beside each other and beside the saturated-steam locus: Profitec’s recommended 124°C at about 1.25 bar sits on that locus…
