Viessmann B0KA Installation And Service Instructions Manual page 74

Troubleshooting
Repairs
(cont.)
3. Check the sensor resistance. Note position of
guide lug B .
■ 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.
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.
Cylinder temperature sensor/outlet temperature
sensor
1. Check lead and plug of the cylinder temperature
sensor or outlet temperature sensor.
2. Disconnect wires of sensor plug.
3. Check the sensor resistance. Compare the resist-
ance with the value for the current temperature
from the following diagram.
In the event of severe deviation (> 10 %), replace
the sensor.
Outside temperature sensor
1. Check the lead and plug of the outside tempera-
ture sensor.
2. Disconnect wires 7 and 8 from terminal 4.
74
3. Check the sensor resistance. Compare the resist-
ance with the value for the current temperature
from the following diagram.
If the results are very different from the curve
(> 10 %), disconnect the wires from the sensor.
Repeat the test directly on the sensor.
Check the on-site lead. 2-core lead, length
up to 35 m with a cross-section of 1.5 mm
Depending on the test result, replace the lead or
the outside temperature sensor.
Flue gas temperature sensor
1. Check the lead and plug of flue gas temperature
sensor .
C
2. Disconnect leads, flue gas temperature sensor
3. Rotate sensor (anti-clockwise) by
it (bayonet fitting).
4. Check the sensor resistance. Compare the resist-
ance with the value for the currently recorded tem-
perature from the following diagram.
In the event of severe deviation (> 10 %), replace
the sensor.
5. Rotate sensor (clockwise) by
Danger
Escaping flue gas can cause poisoning.
When restarting, check for leaks on the flue
gas side.
6. Reconnect leads, flue gas temperature sensor
7. If the permissible flue gas temperature has been
exceeded, the flue gas temperature sensor locks
out the appliance. Reset the burner on the pro-
gramming unit once the flue system has cooled
down.
2
.
C
turn to remove
¼
turn to install it.
¼
.
C