Viessmann VITOCAL 300-G Installation And Service Instructions Manual page 137

Messages
(cont.)
Message
System characteristics Cause
A9 Heat pump
AB Electric heater
Heat pump fault
■ Heat pump faulty
■ Safety high pressure
switch has responded.
■ High pressure or low
pressure sensor has
responded 8 times
within 24 h
■ Fault EEV controller
■ Temperature sensors
in primary/secondary
circuit faulty
Fault, instantaneous
heating water heater
(appliance faulty or high
limit safety cut-out has
responded; alternatively
no temperature rise
within 24 h)
Troubleshooting
Measures
Scan further messages
("Message history" see
page 127); check volume
flow rates, motor currents/
motor protection, and
safety high pressure
switch
Note
After removing fault,
switch appliance OFF and
ON again once.
Danger
Contact with 'live'
components can
lead to severe
injury from elec-
tric current.
Isolate the power
supply prior to
starting work on
the appliance.
137