Saeco RI9722/11, Service Manual

Page: 153 / 224

INCANTO 4. FUNCTION/TIMING
Saeco International Group
REV.5 FEB.2005 Page 9/13
4.4. Flow meter
(Turbine)
The machine is equipped with a flow rate monitoring system. The system checks whether the turbine (flow
meter) rotation speed at a particular time complies with the pre-set value. If no pulses are generated from
the turbine within 10 seconds, the current cycle is interrupted. The Fault - De-aerate signal is indicated. If
this control mechanism is activated, the machine must be de-aerated. During the Water Low signal, the
pump operates at maximum output. As soon as the pump has generated the pre-set flow, the pump output is
reduced to approx. 20 l/hr.
The water quantity is generally controlled according to the coffee quantity programmed through the flow
meter (turbine) pulses.
4.5. HWS valve
(steam operation)
The HWS valve is required for water and steam dispensing, as well as during de-aeration.
If the hot water valve is opened during the brewing process, coffee flow is interrupted and the De-aerate
indicator will appear. As soon as the hot water valve is closed, the brewing process will continue.
The operating temperature during steam dispensing is approx. 125
°
C. The steam button is pressed to
activate steam production (without rapid steam). Steam dispensing occurs via the HWS valve.
The pump pulses the steam dispensed. This means that constant steam dispensing is ensured over a long
period of time. The flow rate of the pump is adjusted on the basis of the thermoblock temperature. If the
temperature is too low, the pump pulses are slowed down. This may occur, for instance, when the hot water
valve opens before the temperature indicator lights up.
Once the steam has been dispensed, the steam valve closes and the steam button must be pressed for
normal operating mode. The overheating indicator flashes until the machine has cooled; the machine
remains locked for coffee dispensing. Cooling can be achieved by opening the HWS valve. The pump
functions at maximum output and the heating remains turned off as long as the Overheating signal remains.
These measures ensure that the cooling process is accelerated and the De-aerate signal will disappear after
a few seconds.
4.6. Temperature sensor (KTY 10)
The temperature sensor is a temperature-sensitive resistance mechanism, converting the boiler temperature
into an electrical signal which is measurable by the CPU.
The CPU compares this signal with the programmed reference signal and, depending on the outcome of the
comparison, controls the boiler output.
The resistance applied has a positive temperature coefficient; i.e. higher boiler temperature - higher sensor
resistance.
The table below indicates the trend in resistance values in relation to the temperature.