Viessmann Vitocal 350-A Installation And Service Instructions Manual page 135

Control unit diagnostics
Message
System characteristics Cause
«30 Flow sensor primary
The heat pump will not
start
«31 Primary return sens.
The heat pump will not
start
«32 Evaporator sensor
«33 Hot gas
«38 Flow sensor primary
The heat pump will not
start
«39 Primary return sens.
The heat pump will not
start
(cont.)
Short circuit, air inlet tem-
perature sensor
Short circuit - air dis-
charge temperature sen-
sor
Short circuit - evaporator
temperature sensor
Short circuit - hot gas
temperature sensor
Break - air inlet tempera-
ture sensor
Break - air discharge
temperature sensor
Troubleshooting
Measures
Check resistance (Pt 500)
at connections 3X1.24
and 3X2.24; replace sen-
sor if required.
Check resistance (Pt 500)
at connections 3X1.23
and 3X2.23; replace sen-
sor if required.
Check pressure drop
value (type Pt 500) at con-
nections 3X1.5 and
3X2.5; replace sensor if
required.
Check pressure drop
value (type Pt 500) at con-
nections 3X1.1 and
3X2.1; replace sensor if
required.
Check resistance (Pt 500)
at connections 3X1.24
and 3X2.24; replace sen-
sor if required.
Check resistance (Pt 500)
at connections 3X1.24
and 3X2.24; replace sen-
sor if required.
135