Viessmann VITOCAL 151-A Installation And Service Instructions Manual page 97

Fault messages
(cont.)
Message code System characteristics
F.14 An outside temperature value
of 0 °C is used to calculate
the set flow temperature.
F.33 Refrigerant circuit off
F.34 Refrigerant circuit off
F.74 The heat pump is switched
off.
F.75 The heat pump is switched
off.
F.87 The safety valve in the indoor
unit has opened.
F.91 Function of connected com-
ponents in emergency mode
Cause
Short circuit, outside tem-
perature sensor
Lead break, air inlet tem-
perature sensor
Short circuit, air inlet tem-
perature sensor
Hydraulic system pressure
too low
No flow in the secondary
circuit, or flow sensor faul-
ty
Hydraulic system pressure
too high
DIO electronics module
communication error
Troubleshooting
Measures
Check resistance value
(NTC 10 k ). Replace sensor if re-
Ω
quired.
Wall mounted indoor unit:
■
Connection on the underside of
the appliance to 6-pole connec-
tion socket on the right, termi-
nals 11 and 12.
Floorstanding indoor unit:
■
Connection at luster terminals for
sensors, terminal 5 and 6
Check resistance value
(NTC 10 k ) at connec-
Ω
tion X16.3/X16.4 of the VCMU re-
frigerant circuit controller. Replace
sensor if required.
Check resistance value
(NTC 10 k ) at connec-
Ω
tion X16.3/X16.4 of the VCMU re-
frigerant circuit controller. Replace
sensor if required.
Top up with water.
Vent the system.
If the fault occurs repeatedly:
Check system pressure sensor
■
with external pressure gauge.
Check the pre-charge pressure
■
of the expansion vessel.
Check settings for set system
■
pressure and range.
Check secondary pump//heating
■
circuit pump, heating/cooling cir-
cuit 1. Replace secondary
pump//heating circuit pump,
heating/cooling circuit 1 if re-
quired.
Check flow sensor. Replace flow
■
sensor if required.
Reduce the system pressure.
Check the settings in the com-
■
missioning assistant. Adjust set-
tings if required.
Check connections to DIO elec-
■
tronics module and connection to
HPMU electronics module.
Check whether components are
■
wrongly connected.
Isolate the system from the pow-
■
er supply. Restart the system.
If the fault persists, replace
DIO electronics module.
97