Viessmann VITOCAL 250-A - Page 178

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A.73 Frequency deviation, compressor speed
A.73
System characteristics
Compressor temporarily off
Cause
Frequency deviation between actual and set compres-
sor speed
Measures
No action required
A.74 Pressure drop in secondary circuit
A.74
System characteristics
■
Unusual operating noise
■
Unusual starting and operational characteristics
Cause
Pressure drop in secondary circuit
Measures
1. Check the expansion vessel.
2. Fill system and vent.
A.75 Pressure spikes in secondary circuit
A.75
System characteristics
■
Unusual operating noise
■
Unusual starting and operational characteristics
Cause
Pressure spikes in secondary circuit
Measures
1. Check the expansion vessel.
2. Check the system pressure. Top up with water and
vent if necessary.
A.80 Fan blocked
A.80
System characteristics
Refrigerant circuit off: Inverter and compressor cannot
be switched on.
Cause
Fan blocked
Measures
1. Check outdoor unit for ice. De-ice if necessary.
2. Check fans can rotate freely.
Messages
Warning messages (cont.)
6218234
Diagnosis