3.4
Check points
Table 4.
Temperatures
Name
Values
Condensing temperature
0.5 – 1.5 °C above supply line temperature
Evaporation temperature
7 - 8 °C
Radiator circuit
8°K temperature difference
Overheating R407C
4K ±1 K
Table 5.
Break pressure switch/pressure transmitter
Refrigerant
Pressure switch/pressure transmitter
Break pressure
R407C
OP (operating pressure switch)
2.85 MPa
High pressure switch
3,10 MPa
Pressure transmitter low pressure
0.04 MPa
Following parameters can be read off in the display:
•
Suction gas temperature
•
Evaporation pressure
•
Evaporation temperature (calculated from ”Dew point”)
•
Opening percent EXV
•
Superheating
This means new opportunities to diagnose the heat pump, without needing to remove the covers and work on the
cooling circuit.
•
In normal operation the heat pump operates with superheating of 5.5°C – 7°C, the expansion valve's degree of
opening will vary depending on operating situation.
•
At outdoor temperatures of -5°C or lower the opening degree is below 20%
•
At outdoor temperatures of +5C to +13°C the opening degree is around 40-50%
•
When cooling (A35W18) the degree of opening is 100%
If superheating is >9°C and the degree of opening of the expansion valve lies steady at 100% this can indicate that
a significant part of the refrigerant has leaked from the heat pump. If this is the case the heat pump must be
checked by service technicians with personal refrigeration certificates!
3.5
Operational problems
The tables list the most probable and common causes of the problem first. When troubleshooting the cause of a
problem start with the first cause and go down the list. There may be more than one way of troubleshooting a
cause where the most probable is given first.
14 – Service instructions VMGFJ102
