english -
23
R
espresso coffee machine - technician instructions
13. VALVE GROUP
The valves are devices whose purpose is to ensure the safety and proper operation of the machine.
13.1 NEGATIVE PRESSURE VALVE
The purpose of the negative pressure valve is to prevent the backflow of liquids through
the steam nozzle when they are being heated. Furthermore, the excess air is eliminated
inside the boiler during the heating phase of the machine.
13.2 SAFETY OR PRESSURE RELIEF VALVE
The pressure relief valve guarantees that the pressure in the boiler does not go above
2 bar. In case of failure of the boiler's monitoring system, the valve can eliminate all the
excess pressure from the boiler.
13.3 EXPANSION - NON-RETURN VALVE
This is a valve consisting of an expansion valve and a non-return valve.
• expansion valve: the cold water sent from the pump to the heat exchangers 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 pressure of the circuit
to 12 bar.
• non-return valve: its function is that of preventing the back flow of water from the
exchangers in the hydraulic circuit.
NOTE
The valves must be checked on a regular basis as described in the chapter "Controls and maintenance".
On all machines with four groups, two pressure relief valves are installed.
EXPANSION
valve
NON-RETURN
valve
12. ANTI-FLOODING DEVICE
The cover installed on the pressure relief valve makes it possible to collect any water
which may leak from the boiler due to malfunction and channel it to the drain pad, by
means of a special hose.
