86
espresso coffee machine - technician instructions
English
12. VALVE GROUP
The valves are devices whose purpose is to ensure the safety and proper operation
of the machine.
12.1 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.
12.2 SAFETY OR PRESSURE RELIEF VALVE
The pressure relief valve guarantees that the pressure in the boiler does not go
above 2 bar. If there is a malfunction to functioning, the capacity of the valve is such
that it can eliminate all the excess pressure from the boiler.
12.3 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 exchanger 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 backflow of water from the
exchanger in the hydraulic circuit.
13. ELECTRONIC CONTROL UNIT
Its purpose is to electronically control the coffee dose by means of the water flowing
through the dosing device and to check the filling of the water in the boiler.
In the EVD model, the volumetric dosing device also electronically controls the
coffee dose by controlling the passage of water through the dosing device.
EXPANSION
valve
NON-RETURN
valve
water
12.4 BY-PASS VALVE
This is valve that is used in models with vi-
bration pumps. It lowers the pressure that the
vibration pump exerts on the water.
BY-PASS
valve
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