Checking The Flue Gas Temperature Sensor; Checking The Temperature Limiter - Viessmann Vitodens 222-F Installation Instructions For Contractors

Maintenance
(cont.)

Checking the flue gas temperature sensor

The flue gas temperature sensor locks out the boiler if
the permissible flue gas temperature is exceeded.
After the flue system has cooled down, press reset
button R to cancel the lock.
Fig. 48
Fault "A3" during commissioning
During commissioning, the control unit checks whether
the flue gas temperature sensor is correctly positioned.
If the flue gas temperature sensor is not positioned
correctly, commissioning is cancelled and fault mes-
sage A3 is displayed.
1. Check whether the flue gas temperature sensor is
correctly inserted. See previous diagram.

Checking the temperature limiter

If the burner control unit cannot be reset after a fault
shutdown although the boiler water temperature is
below approx. 75 °C, check the following:
20
10
8
6
4
2
1
0.8
0.6
0.4
10 30 50 70 90 110
Temperature in °C
Fig. 49 Sensor type: NTC 10 k
1. Disconnect leads from flue gas temperature sensor
.
A
2. Check sensor resistance and compare it to the
curve.
3. In the event of severe deviation replace the sensor.
2. If necessary, correct the position of the flue gas
temperature sensor or replace faulty flue gas tem-
perature sensor.
3. Press reset button R and repeat commissioning.
The check is repeated until it is completed suc-
cessfully.
Troubleshooting
Ω
71