Viessmann WB2-44 - Sensors; Check Outdoor Temperature Sensor; Check Boiler Temperature Sensor

Troubleshooting
40
Correction (continued)
Scanning the actual and desired temperatures
Check outdoor temperature sensor
1. Disconnect connector ”X6” from the
control unit.
2. Measure resistance of outdoor
temperature sensor at the
disconnected connector between
”X6.3” and ”X6.4”, and compare
with resistance/outdoor temperature
curve shown on the left.
3. If the value measured differs
significantly from the curve,
disconnect wires from the sensor
and repeat the measurement directly
on the sensor.
4. Depending on the result, replace
cable or the outdoor temperature
sensor.
Check boiler temperature sensor
1. Disconnect cables from boiler
temperature sensor A.
2. Measure resistance of the boiler
temperature sensor and compare
with resistance/boiler water
temperature curve shown on the
left.
3. If the value measured differs
significantly, replace the sensor.
As the sensor is in direct contact
with the boiler water, the boiler must
be drained before changing the
sensor.
5285 961 v1.3
1 2 43
X6
Outdoor temperature sensor
-40 -22 -04 +50+68+86
400
420
440
460
480
500
520
540
560
580
600
Resistance in Ω
Outdoor temperature in ºF/ºC
-40
-10 0 +10+20+30-30 -20
+14
+32
A
10
1
50 86 122 158 194 230
68 104 140 176 212 248
0.2
0.4
0.6
0.8
2
4
6
8
20
40
Resistance in k
Boiler water temperature in ºF/ºC
10 30 50
20 40 60
70 90 110
80 100 120
Ω
IMPORTANT