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
Two heat-exchanger manufacturer manuals 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 brew water — so the…
Coffee-boiler 95°C is not the 97°C warning or the 93.8°C display
La Marzocco Strada AV and Linea PB operating manuals attach three different coffee-boiler temperature kinds of claim that do not coincide: Strada’s parts description prints an adjustable operating temperature of 95°C; the same manuals’…
Fifteen bar on the Ulka E5 curve is zero flow
CEME/Ulka’s Family E high-pressure flow table — where model E5 shows 0 cc/min average flow at 15 bar — sits 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
Nine bar’s status as convention is documented, but the claim that Gaggia’s lever spring produced it is not; the figure is applied to three pressures; the familiar 1.5 bar gauge-to-puck offset traces to a single 2021 forum post about one…
124°C at 1.25 bar is not the same steam-boiler pair as 120°C at 1.2 bar
Manufacturer steam/service-boiler pairings of PID-displayed temperature with boiler-gauge pressure sit beside each other and beside the saturated-steam locus: Profitec’s recommended 124°C at about 1.25 bar sits on that locus under a gauge…
