17
FO 935
ALARMS AND VENTILATION
Carry out the electrical connections on the removable terminal blocks only after disconnecting them from the unit.
When the control unit is in one of the modes indicated below it does not perform any thermal monitoring, moreover the
relays will all be disabled. The fault contact switches and the fault LED flashes.
•
Programming viewing display.
•
PRG programming.
•
Relay test.
The ALARM and TRIP relays only switch when the set temperature thresholds are exceeded.
The FAULT (fault) contact, programmed in active failsafe mode (default YES), opens (11-12) when the appliance is
powered, only if during the access phase the control unit does not detect anomalies, and keeps the switching until when
one of the following events occurs:
•
Data memory fault (Ech message).
•
FO sensor fault (FCC-FOC-FLT)
•
CFO 521 concentrator disconnected (TEC)
•
Insufficient supply voltage.
•
During the power on reset after programming (PRG), displaying of the data (VIS) and relay test.
The FAULT failsafe mode can be disabled FAULT failsafe "NO" see programming step 30-31 page 20.
NOTE: in order to avoid unwanted system outages, do not connect the FAULT relay to the transformer tripping circuit.
FAULT AND RESET MESSAGE SEQUENCE
Find below the sequence of fault messages and RESET function condition.
1) ECH
2) TEC
3) FO FCC
4) FO FOC
5) FO FLT
The FAN1 and FAN2 contacts can be used to control the cooling fans, or they can be inserted in the conditioning system
of the transformer room, see paragraph cooling fan control on page 18.
NOTE: always disconnect the unit before performing any electrical connections.
eeprom fault
concentrator communication bus fault
min. temperature full scale exceeded
max. temperature full scale exceeded
broken or disconnected fibre optic sensor
erasable message
non-resettable condition
non-resettable condition
non-resettable condition
non-resettable condition
FO SENSOR DIAGNOSTICS
In case of breakage or exceeding of the minimum/ maximum full scale value of one of the FO sensors installed on the
machine to be protected, the FAULT relay is instantaneously switched, with the relative sensor failure indication on the
corresponding channel.
Display message
FCC:
exceeding of the minimum full scale value = measured temperature <-35°C
Display message
FOC
: exceeding of the maximum full scale value = detected temperature > 195°C
ATTENTION: the FLT indication appears on the display when the concentrator identifies a faulty or disconnected FO
sensor.
To eliminate the message and to restore the Fault switching, check the connections of the FO sensors and replace the faulty
sensor if necessary. In case the minimum/maximum full scale value has been reached, make sure that the environmental
conditions correspond to what is indicated by the control unit.
Note: exceeding of the minimum/ maximum full scale can also be caused by possible disturbances on the communication
lines or by strong magnetic fields; in this case, the following is recommended:
Check the correct installation of the sensors and especially of the extension cable between the CFO 521 concentrators and
the FO 935 control unit.
FAULT CONTACT OPERATION (failsafe active)
FAULT 11-12 NC: ALARM FAULT OR POWER OFF
FAULT 11-12 NO: POWER ON OR NO FAULT
