Viessmann VITOTRONIC300 Installation And Service Instructions Manual page 70

Troubleshooting
Fault Display
(continued)
Displayed System characteristics
fault code
44 Mixing valve is being closed.
48 Mixing valve is being closed.
4C Mixing valve is being closed.
50 DHW tank primary pump "ON":
Set DHW temperature = set supply
temperature
Priority control is cancelled.
or
With primary store system:
DHW tank heating is started and stopped
by DHW tank temperature sensor 2.
51 With primary store system:
DHW tank heating is started and stopped
by DHW tank temperature sensor 1.
52 Control mode.
58 DHW tank primary pump "ON":
Set DHW temperature = set boiler water
temperature
Priority control is cancelled.
or
With primary store system:
DHW tank heating is started and stopped
by DHW tank temperature sensor 2.
70
Vitotronic 300, GW2B Installation and Service
Cause
Short circuit, supply
temperature sensor, heating
circuit with mixing valve M3
(heating circuit 3)
Lead break, supply temperature
sensor, heating circuit with
mixing valve M2
(heating circuit 2)
Lead break, supply temperature
sensor, heating circuit with
mixing valve M3
(heating circuit 3)
Short circuit, DHW tank
temperature sensor 1
Short circuit, DHW tank
temperature sensor 2
Short circuit, supply
temperature sensor low loss
header
Lead break, DHW tank
temperature sensor 1
Measures
Check the supply
temperature sensor
(see page 124).
Check the supply
temperature sensor
(see page 124).
Check the supply
temperature sensor (see
page 124).
Check the DHW tank
temperature sensor
(see page 124).
Check the DHW tank
temperature sensor
(see page 124).
Check the supply
temperature sensor
(see page 124).
Check the DHW tank
temperature sensor
(see page 124).