Viessmann Vitodens 200-W Installation And Service Instructions Manual page 120

Troubleshooting
Fault codes
(cont.)
Dis- Const.
played
fault
code
1b X
1F X
20 X
28 X
30 X
38 X
40
44
120
Weath.- System char-
comp. acteristics
X Burner blocked Flow sensor 2
X Burner blocked Differential
X Regulates with-
out flow tem-
perature sen-
sor (low loss
header)
X Regulates with-
out flow tem-
perature sen-
sor (low loss
header)
X Burner blocked Short circuit,
X Burner blocked Lead break,
X Mixer closes
X Mixer closes
Cause Measures
Replace sensor
faulty (see page 138).
Clean heat ex-
flow rate too changer by flush-
large ing.
Short circuit, Check low loss
system flow header sensor (see
temperature page 136).
sensor
Lead break, Check low loss
system flow header sensor (see
temperature page 136).
sensor If no low loss head-
er sensor is con-
nected, set code
52:0.
Check boiler water
boiler water temperature sen-
temperature sors (see
sensor page 136).
Check boiler water
boiler water temperature sen-
temperature sors (see
sensor page 136).
Short circuit, Check flow temper-
flow tempera- ature sensor (see
ture sensor, page 142).
heating circuit
2 (with mixer)
Short circuit, Check flow temper-
flow tempera- ature sensor (see
ture sensor, page 142).
heating circuit
3 (with mixer)