USER MANUAL
Spirit User manual
page 16
Shot timers
The timers on top of each group (see Figure 13) measure the time in seconds that the corresponding
group valve is open and thus indicate the brew-time. As soon as the group valve opens the time is set
to zero and counting starts. The timer stops counting when the group valve is closed and the
measured time between opening and closing of the group valve is displayed until the group valve is
opened again.
The shot time gives an excellent indication of the brew process and can assist the trained barista to
refine that process.
Figure 13. The Spirit shot timers.
A pre-set amount of water will pass through the machine when the brew process is started. Pump
pressure and diameter of smallest duct in the set-up (generally the restrictor underneath the group-
valve) determine
the “free flow” rate (the flow rate when no filter holder with coffee bed is locked in).
During the pre-infusion phase, the combination of pump pressure, size of the restrictor, optional Idro-
matic and the coffee bed characteristics determine flow rate onto the coffee bed. The starting pressure
in the coffee boiler may fluctuate between 9 and 13 Bar but has very minor influence.
During the extraction phase, it is mainly pump pressure and coffee bed characteristics that determine
the flow rate. Variables in the coffee bed are numerous, the most important depend on the grinder
(amount of coffee particles and particle size distribution) and the barista (levelling and tamping of
coffee and thus packing of particles). Other variables in the coffee bed are: roasting grade, freshness
and air humidity.
Duri
ng “free flow” the timer gives an indication of the condition of the smallest restrictor in the
espresso machine which, depending on individual set-up, has an orifice of 0.5
– 0.8 mm. With such
small openings, even a minor divergence can cause quite a large difference in free flow rate.
Production variances of the restrictors are known to cause a difference in free-
flow “shot time”
between groups of up to 15%.
Notes!
Measuring the free flow time will only give a rough indication of (smallest) restrictor size and will give
no information about pre-infusion and/or extraction. Only with a filled and tamped filter holder in the
group can timing measurements be used to give information about pre-infusion and extraction phase.
During the extraction phase, the coffee-bed in the filter is completely dominant in terms of flow rate
and any production variations in restrictor sizes are completely swamped by the restrictive effect of the
coffee-bed.
shot timers
