Viessmann VITOTRONIC 200 Service Instructions Manual page 51

Messages
(cont.)
Message
Code/system characteris-
tics
AA Cancel defrost
Compressor remains off
until the temperature in
the secondary circuit has
reached 15 °C. For this,
the booster heaters may
be switched on.
AB Instant.htg wtr heater
Instantaneous heating
water heater will not be
started.
Cause
Inadequate flow or return
temperature in the sec-
ondary circuit for defrost-
ing.
■ Fault, instantaneous
heating water heater
(appliance faulty, high
limit safety cut-out has
responded, or no tem-
perature rise within
24 h).
■ Temperature limiter in
instantaneous heating
water heater set too
low.
Troubleshooting
Measures
!
Please note
If the tempera-
ture in the secon-
dary circuit is
inadequate, the
condenser may
freeze up or a
thick layer of ice
may form on the
evaporator.
Do not acknowl-
edge the fault
message until the
flow temperature
in the secondary
circuit has
reached 15 °C.
Danger
Contact with 'live'
components can
cause severe
injury from elec-
tric current.
Isolate the power
supply prior to
starting work on
the appliance.
■ Check power supply,
connecting cable and
plug for the instantane-
ous heating water
heater.
51