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F.1259 Modbus communication fault, refrigerant circuit controller (VCMU) to inverter
F.1259
System characteristics
Refrigerant circuit off
Cause
No communication between inverter and heat pump
control unit
Measures
1. Isolate the outdoor unit from the power supply. Wait
at least 2 min. Switch on voltage again.
2. Check connections X11.1 to X11.3 on the
VCMU refrigerant circuit controller and the Modbus
connection on the inverter:
■
Check wires and plugs for correct seating.
■
Check connections for contact corrosion.
■
Check cables for mechanical damage, e.g. crush-
ing, kinking, chafing or breakage.
Replace Modbus cable if necessary.
3. Check the power supply at plug X1 on the
VCMU refrigerant circuit controller.
4. Replace VCMU refrigerant circuit controller.
5. Replace inverter.
Warning messages
A.2 Frost protection limit undershot
A.2
System characteristics
■
Frost protection enabled
■
Heat demand, heat pump running.
■
DHW circulation pump enabled
Cause
Outside temperature has undershot the specified frost
protection limit.
Measures
No action required
A.11 System pressure too low
A.11
System characteristics
Room heating/room cooling only for some rooms
Cause
System pressure too low
Measures
Top up with water.
Messages
Fault messages (cont.)
6218234
Diagnosis
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