Douwe Egberts Cafitesse 700, Back Office Manual

Page: 167 / 265

July 2004
5A - 25
Functions - water system
• The watchdog relay on the control system
circuit board interrupts the safety circuit
whenever the control system detects a
dangerous state.
• The boil over sensor and the dry running
protection function independently of the
control system and protect the hot water
system in case the electronic control system
does not function correctly.
• If the safety circuit is interrupted, an error is
indicated in the display.
Software safety against
overheating/boiling over
• The following functions of the electronic
control system protect the hot water system
from overheating or boiling over:
1. Temperature regulating function:
T > T
setpoint
Whenever the desired (programmed)
temperature is exceeded, the heating
system is switched off via the relays.
2. Interruption of the safety circuit in case
of:
T > T
setpoint
+ 5 K
The watchdog relay is opened whenever
the sensor detects an impermissibly high
boiler temperature (more than 5 K above
the setpoint temperature).
In case of a relay malfunction, this is
supposed to prevent the safety circuit
from not switching off until the boil over
sensor is activated by a high development
of steam. (T > 101
°
C / 214
°
F)
3. Interruption of the safety circuit in case
of a control system malfunction.
In case of an error in the program se-
quence of the microprocessor, the watch-
dog relay is opened automatically.
Software function:
Filling level electrode as dry running protec-
tion
• The heating system is switched off via the relay
whenever the filling level electrode detects a
water level which is too low for more than 30 sec.
• If this system is not functioning properly, the
safety circuit is interrupted by the electronic
dry running protection.
Software protection against overflow of the
boiler
• If the water inlet system is not able to fill up
the boiler within 1 min., the watchdog relay
interrupts the safety circuit. Among other
devices, the inlet valve is then also switched
off. (The display also shows an error mes-
sage.)
• The time counts from when a low level has
been detected via the filling level electrodes.
• Though in case of a Power-ON-Reset (the
mains plug is unplugged and plugged back),
a longer period time of is granted for the
filling procedure: 2.5 min., after that the
display shows an error message.
• Whenever a malfunction occurs, the
watchdog relay switches off.
The heating system switches off.
ATTENTION: The switching function must
be checked following any
repair work.
Cafitesse 700 - Functions - water system