Viessmann Vitocrossal 300 CA3 2.5 Installation And Service Instructions Manual page 178

Troubleshooting
Boiler System Fault Codes
Displayed System characteristics
fault code
4c Mixing valve is being closed.
50 Tank loading pump on:
DHW temperature target =
set supply temperature
Priority control is cancelled.
52 Control mode
58 Tank loading pump on:
DHW temperature target =
set supply temperature
Priority control is cancelled.
5a Control mode
60 Boiler with maximum
temperature, no output
reduction, mixing valve return
temperature control open
68 Boiler with maximum
temperature, no output
reduction, mixing valve return
temperature control open
70 Shunt pump constantly ON.
With tank loading system:
close 3-way mixing valve;
no DHW heating
78 Shunt pump constantly ON
With tank loading system:
close 3-way mixing valve;
no DHW heating
80 If a fault occurs 3 x in 15 min.,
fault is displayed. Burner control
unit goes into a fault state,
system cools down, burner
control unit locked out.
81 Burner control unit in a fault sate Sensor drift, boiler water
82 Burner control unit in a fault
state, system cools down,
burner control unit locked out.
178
Vitocrossal 300 CA3 Series 2.5 to 6.0 Installation/Service
(continued)
Cause
Lead break, supply temperature
sensor, heating circuit with mixing
valve M3 (heating circuit 3).
Short circuit, tank temperature
sensor 1
Short circuit, supply temperature
sensor low loss header.
Lead break, DHW tank
temperature sensor 1.
Lead break, low loss header
supply temperature sensor.
Short circuit, temperature sensor
aJA.
Lead break, temperature sensor
aJA.
Short circuit, temperature
sensor aJB.
Lead break, temperature sensor
aJB.
Short circuit, boiler water
temperature sensor, burner
control unit
temperature sensor, burner
control unit
Short circuit, flue gas temperature
sensor (A or B), burner control unit
Measures
Check supply temperature
sensor.
Check tank temperature
sensor.
Check supply temperature
sensor.
Check DHW tank temperature
sensor.
Check supply temperature
sensor (see page 186).
Without supply temperature
sensor:
Set code "52:0" in the
"General" group.
Check temperature sensor.
Check temperature sensor.
Without temperature sensor:
Set coding "4a:0" in the
"General" group.
Check temperature sensor.
Check temperature sensor.
Without temperature sensor:
Set code "4b:0" in the
"General" group.
Check connection cable and
dual sensor; replace sensor if
required.
Check connection cable and
dual sensor; replace sensor if
required.
Check connection cable and
sensors (A and B), replace
sensors if required.