Viessmann VITODENS 222-F Service Instructions Manual page 79

Vitodens 222-F B2TA 19 and 35 Service
Corrective Action
(continued)
Check boiler temperature sensor, tank temperature
sensor, supply temperature sensor of the low-loss header
or room temperature sensor
1. Boiler temperature sensor:
Remove lead to boiler water temperature sensor A
and check the resistance.
DHW Tank temperature sensor:
Pull plug % from the cable harness at the control
unit and check the resistance.
Supply temperature sensor or Low-loss header
temperature sensor ?:
Pull plug "X3" from the control unit and check the
resistance across terminals "X3.4" and "X3.5".
Note: Only one temperature sensor ? may be used.
2. Check the sensor resistance and compare the actual
values with the curve.
3. Replace the sensor in the case of severe deviation.
Sensor type: NTC 10 kΩ
WARNING
The boiler temperature sensor is immersed in the heating
water (risk of scalding). Drain the boiler before replacing
the sensor.
Temperature sensors
Troubleshooting
79