Douwe Egberts Cafitesse 50, Service Manual

Page: 52 / 106

Functions (water) - 12
Version 1.36
02/2004
Overflow prevention
If water exceeds the maximum level, it will flow into the overflow tube and is flowing out of the machine.
A thermistor is mounted next to the hose. When the thermistor detects the presence of hot water
(>63°C/145°F ± 5°C/9°F) it will activate the safety circuit, the LED above the main switch starts blinking
and power is shut off. The machine can be reset by means of a switch that can be reached through an
opening at the rear side of the machine.
Dry running prevention
The dry running prevention is operated by temperature detection (bi-metal) integrated in the heating
element connector.
When the boiler temperature exceeds the limit of 4°C/7°F above the set temperature, normally the
relay will switch off the power supply. Should the NTC sensor fail to detect a high temperature, the
power remains on, the temperature increases and the bi-metal is actuated.
The deformed bi-metal plate presses against a small pin that in turn disconnnects the leads inside the
connector and the heating element will be switched off. The bi-metal plate will restore its shape when
the boiler temperature has dropped to normal.
There is furthermore a pin at the rear side the connector that functions as a second (back-up) safety
component.
In the remote case that the bi-metal safety device fails to disconnect the heating element, this (plastic)
pin will melt. When this occurs, the leads inside the connector are disconnected by spring pressure.
The heating element should be discarded if this safety device has been actuated.