Viessmann VITOCAL 250-A - Page 173

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F.1217 Loss of communication with the lag heat pump
F.1217
System characteristics
Limited operation of the heat pump cascade
Cause
■
No mains voltage
■
The slave heat pump is off.
■
The slave heat pump was not commissioned cor-
rectly.
■
Communication fault, CAN bus
Measures
1. Check the power supply to the slave heat pump.
2. Isolate the slave heat pump from the power supply.
Wait at least 4 min. Switch on voltage again.
3. Check the following CAN bus connections:
■
Connection X8.1 to X8.3 on plug 91 on HPMU
electronics module
■
Wall mounted indoor unit: Connection on device
underside, 6-pole connection socket on the left,
terminals 1.CAN L to 3.CAN H
■
Floorstanding indoor unit: Connection to luster ter-
minals for bus connections, terminals 91.CAN L to
91.CAN H
■
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.
■
Check CAN L/CAN H assignment.
■
CAN Ground (GND) must not be connected.
■
Check cable type: Li2YCYv, twisted pair, shielded
or 2-core CAT5, shielded
■
Check cable length.
■
Check the position and number of terminators.
4. Check the settings in the commissioning assistant.
Restore factory settings if necessary.
5. Check the software versions of the HPMU and
EHCU electronics modules in ViGuide. Update if
necessary.
F.1254 Safety shutdown, thermal overload protection, compressor if the compressor starts up
several times
F.1254
System characteristics
■
Output demand to heat pump not possible
■
Compressor switched off
Cause
Thermal overload of the compressor after multiple
start-ups
Measures
1. Check all connections to the compressor:
■
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 cable if necessary.
2. Have parameters of compressor checked by
Viessmann Technical Service.
3. Isolate the outdoor unit from the power supply. Wait
at least 2 min. Switch on voltage again.
4. Replace compressor.
Messages
Fault messages (cont.)
6218234
Diagnosis