97
Sensor
Test el-
ement
Installed loca-
tion
Connection
■ Collector temperature sensor
(F21)
NTC
20 kΩ
Internal unit (see
page 90)
Controller and
sensor PCB (see
page 42)
■ Compressor head temperature
sensor (hot gas) (CTT)
NTC
50 kΩ
External unit
(see page 92)
Refrigerant circuit
controller (ob-
serve label on the
external unit)
Temperature sensors in the internal unit (with ID)
Viessmann NTC 10 kΩ (marked blue)
Outside temperature sensor
100
10
-20 -10 0 10 20 30
Temperature in °C
6
8
20
40
60
80
200
Resistance in k
Ω
Other sensors
10
1
10 30 50 70 90 110
Temperature in °C
0.4
0.6
0.8
2
4
6
8
20
Resistance in k
Ω
Troubleshooting
Repairs
(cont.)
5546 699 GB
Service
