Viessmann WB1A007 - Page 65

Troubleshooting
65
Correction
Remove front cover panel
1. Remove the screw at the top of the
boiler.
2. Press down the springs on the
underside of the boiler.
3. Remove the front cover panel.
4. Lift the front cover panel from the
wall mounting frame.
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.
5581 775 1.3
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
4
0
R
e
s
i
s
t
a
n
c
e
i
n
k
Boiler water temperature in ºF/ºC
10 30 50
20 40 60
70 90 110
80 100 120
Ω
The boiler temperature sensor is
immersed in the heating water (risk
of scalding).
Drain the boiler before replacing the
sensor.
WARNING