Viessmann VITODENS 222-F Installation And Service Instructions Manual page 120

Troubleshooting
Repairs
(cont.)
Draining the boiler on the heating water side
1. Close the shut-off valves on the heat-
ing water side.
2. Route hose at drain valve A into a
suitable container or drain outlet.
Checking the outside temperature sensor (weather-compensa-
ted control unit)
120
3. Open drain valve A and drain the
200
X3
100
Sensor type: NTC 10 kΩ
boiler as much as required.
80
60
40
20
10
8
6
-20 -10 0
Temperature in °C
10 20 30