Viessmann Vitocal 350-A Installation And Service Instructions Manual page 142

Troubleshooting
Control unit diagnostics
Message
System characteristics Cause
«AD Mixer heat./DHW
¸AE DHW sensors swapped
142
(cont.)
Three-way diverter valve
"Central/DHW heating"
faulty
Cylinder temperature
sensors top/bottom inter-
changed
Measures
■ Check power supply,
power cable and plug to
the instantaneous heat-
ing water heater
■ Test instantaneous
heating water heater
control signal at con-
nections 2X7.5 (stage
2) and 2X8.8 (stage 1);
check high limit safety
cut-out and reset if
required; check instan-
taneous heating water
heater.
Installation
instructions,
instantaneous
heating water
heater
Check three-way diverter
valve for function (menu
"Manual control")
Test connection 2X7.10
and replace if required.
No measures required.
The heat pump control
unit interchanges the sen-
sors internally.