Checking The Temperature Sensors - Viessmann VITODENS 111-W Installation And Service Instructions Manual

Troubleshooting
Repairs
(cont.)

Checking the temperature sensors

4
2
B
1 3
1 2
3 4
A
Fig. 45
Heat generator circuit flow temperature sensor
(dual sensor)
1. Check the leads and plugs of flow temperature
sensors .
A
2. Disconnect the leads from flow temperature sen-
sors .
A
96
C
3. Check the sensor resistance. Note position of
guide lug
Sensor 1: Connections 1 and 3
■
Sensor 2: Connections 2 and 4
■
Compare the resistances with the value for the cur-
rent temperature from the following diagram. In the
event of severe deviation (> 10 %), replace the
dual sensor.
.
B
Danger
The dual sensor is directly immersed in the
heating water (risk of scalding).
Drain the boiler on the heating water side
before replacing the sensor.
Danger
Risk of electric shock from escaping heating
water.
Check the dual sensor for leaks.