Viessmann VITOCAL 300-G Installation And Service Instructions Manual page 130

Troubleshooting
Messages
(cont.)
Message
System characteristics Cause
28 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)
29 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)
2A 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)
30 Flow sensor primary
Operation with tempera-
ture value of return tem-
perature sensor in pri-
mary circuit, plus 3 K. If
both temperature sen-
sors (primary flow and
return) are faulty, the
heat pump stops (mes-
sage A9)
130
Lead break, secondary
circuit flow temperature
sensor
Lead break, return tem-
perature sensor, secon-
dary circuit, heat pump
stage 1 (type BW)
Lead break, return tem-
perature sensor, secon-
dary circuit, heat pump
stage 2 (type BWS)
Short circuit, tempera-
ture sensor, primary cir-
cuit (heat pump brine
inlet)
Measures
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.
Check resistance (Pt 500)
at plug-in connection F2
and terminals X5.2/X5.3;
replace sensor if
required.