Viessmann Vitocal 350-A Installation And Service Instructions Manual page 143

Control unit diagnostics
Message
System characteristics Cause
«AF Cylinder primary pump
«B0 Device recognition
«B1 KM BUS EEV
(cont.)
■ Circulation pump for
cylinder heating (heat-
ing water side) faulty
■ Circulation volume in
primary store system
too low; cylinder pri-
mary pump (DHW
side) or two-way valve
on primary store sys-
tem faulty.
Error in recognising
appliance version, incor-
rect coding card or PCBs
faulty.
Communication error
with EEV controller
(refrigerant circuit con-
trol)
Troubleshooting
Measures
■ Circulation pump for
cylinder heating:
Test voltage at connec-
tion 2X7.10 and check
pump mechanically;
replace if required.
■ Cylinder primary pump/
two-way valve:
Test voltage at connec-
tion 2X8.12 and check
pump/valve mechani-
cally; replace if
required.
■ Check sensor input F11
on PCB 3. Do not con-
nect anything to con-
nections 3X1.11 and
3X2.11.
■ Check coding card and
replace if required.
■ Check PCBs and
replace if required.
Check KM BUS connec-
tion. At the connection
between KM BUS and
EEV at terminals 3X5.14
and 3X5.15, a fluctuating
DC voltage between
approx. 20 V and 30 V can
be measured (connec-
tions are parallel to
3X1.25 and 3X2.25).
Check leads/cables;
check power supply to
EEV controller PCB;
replace PCB if required.
143