System Status; Testing The Temperature Sensors - Viessmann PLC VITOCAL 350-HT PRO Service Instructions For Contractors

System status

Launch with
Fig. 37
This page provides information on the various system
statuses.
A green dot indicates an enable or normal operation.
■
■ A red dot indicates that there is no enable or that a
malfunction is present.
Conditions for enabling the heat pump:
System mains isolator ON
■
Emergency stop button inactive
■

Testing the temperature sensors

All temperature sensors used are Pt1000 sensors.
The control system reports a temperature sensor fault
if the measured temperature is not within the possible
range.
Example:
Outside temperature above 100 °C
Error messages also appear if there is a break in the
power cable or if the resistance has dropped due to
moisture and dirt on the connections.
■ PSU enable present
No priority 1 alarm active
■
Heating or cooling demand present
■
■ Pump out, heating water buffer cylinder charging,
coolant buffer cylinder charging or DHW cylinder
charging is switched on
At least one compressor enable is present
■
To find out the resistance, and consequently the meas-
ured temperature, at least one of the two connections
between the sensor and the control system should be
disconnected. Then measure the resistance with an
ohmmeter and compare the result with the curve. Val-
ues that are too high suggest a poor connection. Val-
ues that are too low suggest unwanted contact due to
moisture or dirt.
Diagnosis
51