Astoria SABRINA SAE DISPLAY Use And Maintenance Manual page 16

Sabrina
3.11.1 Steam heating unit
The heating unit is made of copper sheet metal (1).
The heat exchangers are assembled onto this unit and
are in turn connected to the dispensing group. The water
used for dispensing coffee is taken directly from the heat
exchanger. During the dispensing process, cold water is
sent inside the exchanger by means of the motor pump.
Cold water and the pre-existing hot water are mixed to-
gether inside the heat exchanger, in order to obtain the
optimal water temperature for coffee infusion.
The heating unit is electrically heated by an electric
heating element immersed in the water (2).
1
3.11.2 Overflow device
The cover installed on the pressure relief valve makes
it possible to collect any water and steam which may leak
from the heating unit due to a malfunction and channel
it to the drain tray, via a special hose.
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2
3.11.3 Pressure relief safety valve
The pressure relief safety valve has a calibra-
tion of 1.9 bar in order to ensure that the pres-
sure in the steam heating unit does not exceed
2.1 bar. Should a fault occur, the capacity of the
valve is such as to be able to eliminate all the
excess pressure in the heating unit.
The safety valve should be checked regularly as indicated in Chap.
9.3 on page 46.
Two safety valves are installed on all machines with 4 groups.
3.11.4 Expansion valve + check valve
This is a valve consisting of an expansion valve and
a check valve.
Expansion valve (A):
the cold water sent from the pump to the heat ex-
changers is heated. This heating
causes an increase in the volume
of water. To limit pressure increases
in the hydraulic circuit, the valve
limits the maximum internal pres-
sure of the circuit to 12 Bar.
Check valve (B):
its function is to prevent the water
from back-flowing into the ex-
changers in the hydraulic circuit.
3.11.5 Negative pressure valve
The purpose of the negative pressure valve
is to prevent liquids from back-flowing through
the steam nozzle when they are being heated.
Furthermore, the excess air inside the heating unit
is removed during the machine's heating phase.
3.11.6 Pressure switch
The pressure switch makes it possible
to control the heating unit pressure by
activating or bypassing the heating el-
ement in the heating unit. Any pressure
switch calibration can be carried out with
the machine in operation by turning the
screw (6) located on the body of the
component (SAE) or inside (SAE DISPLAY).
A
B
SAE
6
SAE DISPLAY
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