Viessmann VITOTRONIC 200 Service Instructions Manual page 38

Troubleshooting
Messages
(cont.)
Message
Code/system characteris-
tics
0D Test mode ext. unit
Heat pump heats or cools
with a constant flow tem-
perature in the secon-
dary circuit; secondary
pump starts.
Set flow temperature for
test mode:
■ Cooling 16 °C
■ Heating 30 °C
10 Outside temp. sensor
Operation with outside
temperature –40 °C.
18 Outside temp. sensor
Operation with outside
temperature –40 °C
20 Flow sensor secondary
Operation with tempera-
ture value of return tem-
perature sensor in sec-
ondary circuit plus 5 K.
Heat pump is shut down
if both temperature sen-
sors are faulty (secon-
dary flow and return)
(message A9).
38
Cause
External unit in test
mode.
Short circuit, outside
temperature sensor.
Lead break, outside tem-
perature sensor.
Short circuit, secondary
circuit flow temperature
sensor
Measures
Test mode can be termi-
nated at the external unit.
To do this, hold down
"Mode" key on the exter-
nal unit for 5 s.
Check resistance (Ni 500)
at plug-in connection F0
(see page 172); replace
sensor if required.
Check resistance (Ni 500)
at plug-in connection F0
(see page 172); replace
sensor if required.
Check resistance (Pt 500)
at plug-in connection F8 or
terminals X5.8/X5.9 (see
page 172); replace sen-
sor if required.