Fault Codes - Viessmann FB2B Installation And Service Instructions Manual

Troubleshooting

Fault codes

Displayed System characteris-
fault code tics
10 Regulates as if the
outside temperature
was 0 °C
18 Regulates as if the
outside temperature
was 0 °C
20 Regulates without
flow temperature
sensor (low loss
header)
28 Regulates without
flow temperature
sensor (low loss
header)
30 Burner blocked
38 Burner blocked
40 Mixer closes
44 Mixer closes
48 Mixer closes
4C Mixer closes
50 No DHW heating
104
Cause Measures
Short circuit, out- Check the outside tem-
side temperature perature sensor (see
sensor page 116).
Lead break, out- Check the outside tem-
side temperature perature sensor (see
sensor page 116).
Short circuit, sys- Check the low loss header
tem flow tempera- sensor (see page 117)
ture sensor
Lead break, sys- Check the low loss header
tem flow tempera- sensor (see page 117)
ture sensor
Short circuit, boiler Check the boiler water
water temperature temperature sensor (see
sensor page 117)
Lead break, boiler Check the boiler water
water temperature temperature sensor (see
sensor page 117)
Short circuit, flow Check flow temperature
temperature sen- sensor
sor, heating circuit
2 (with mixer)
Short circuit, flow Check flow temperature
temperature sen- sensor
sor, heating circuit
3 (with mixer)
Lead break, flow Check flow temperature
temperature sen- sensor
sor, heating circuit
2 (with mixer)
Lead break, flow Check flow temperature
temperature sen- sensor
sor, heating circuit
3 (with mixer)
Short circuit, cylin- Check sensors (see
der temperature page 117)
sensor