Viessmann VITOCAL 300-G Installation And Service Instructions Manual page 129

Messages
(cont.)
Message
System characteristics Cause
18 Outside temp sensor
Operation with outside
temperature -40 °C
20 Flow sensor secondary
Operation with tempera-
ture value of return tem-
perature sensor in sec-
ondary circuit, plus 5 K. If
both temperature sen-
sors (secondary flow and
return) are faulty, the
heat pump stops (mes-
sage A9)
21 Return sensor sec.
Operation with tempera-
ture value of flow temper-
ature sensor in secon-
dary circuit, minus 5 K. If
both temperature sen-
sors (secondary flow and
return) are faulty, the
heat pump stops (mes-
sage A9)
22 Return sensor sec. 2
Operation with tempera-
ture value of flow temper-
ature sensor in secon-
dary circuit, minus 5 K. If
both temperature sen-
sors (secondary flow and
return) are faulty, the
heat pump stops (mes-
sage A9)
Lead break, outside tem-
perature sensor
Short circuit, secondary
circuit flow temperature
sensor
Short circuit, return tem-
perature sensor, secon-
dary circuit, heat pump
stage 1 (type BW)
Short circuit, return tem-
perature sensor, secon-
dary circuit, heat pump
stage 2 (type BWS)
Troubleshooting
Measures
Check resistance (Ni 500)
at plug-in connection F0;
replace sensor if
required.
Check resistance (Pt 500)
at plug-in connection F8
and terminals X5.8/X5.9;
replace sensor if
required.
Check resistance (Pt 500)
at plug-in connection F9
and terminals X5.10/
X5.11; replace sensor if
required.
Check resistance (Pt 500)
at plug-in connection F18
and terminals X6.6/X6.7;
replace sensor if
required.
129