Viessmann VITOCAL 151-A Installation And Service Instructions Manual page 105

Fault messages
(cont.)
Message code System characteristics
F.687 The heat pump is switched
■
off.
No function of connected
■
components
F.770 Refrigerant circuit off
F.771 Refrigerant circuit off
F.772 Refrigerant circuit can only
be operated when outside
temperatures are above 5 °C
F.773 Refrigerant circuit can only
be operated when outside
temperatures are above 5 °C
F.788 No room heating/cooling
■
No DHW heating
■
F.790 No room heating/cooling
■
No DHW heating
■
F.791 Reduced output, instantane-
ous heating water heater
F.792 Reduced output, instantane-
ous heating water heater
Cause
EHCU electronics module
communication error
Lead break, flow tempera-
ture sensor, secondary cir-
cuit downstream of con-
denser
Short circuit, flow temper-
ature sensor, secondary
circuit downstream of con-
denser
Lead break, oil sump tem-
perature sensor
Short circuit, oil sump
temperature sensor
Fault, control and/or pow-
er supply of 4/3-way valve
Motor of 4/3-way valve
■
not correctly mounted
4/3-way valve faulty
■
Phase L1 in power supply
of instantaneous heating
water heater not present
Phase L2 in power supply
of instantaneous heating
water heater not present
Troubleshooting
Measures
Check connections on EH-
■
CU electronics module.
Check whether components are
■
wrongly connected.
Isolate the system from the pow-
■
er supply. Restart the system.
If the fault persists, replace the
EHCU electronics module.
Check resistance value
(NTC 10 k ) at connec-
Ω
tion X15.3/X15.4 of the VCMU re-
frigerant circuit controller. Replace
sensor if required.
Check resistance value
(NTC 10 k ) at connec-
Ω
tion X15.3/X15.4 of the VCMU re-
frigerant circuit controller. Replace
sensor if required.
Check resistance value
(NTC 10 k ) at connec-
Ω
tion X20.3/X20.4 of the VCMU re-
frigerant circuit controller. Replace
sensor if required.
Check resistance value
(NTC 10 k ) at connec-
Ω
tion X20.3/X20.4 of the VCMU re-
frigerant circuit controller. Replace
sensor if required.
Check connections on motor of
■
4/3-way valve.
Check motor of 4/3-way valve.
■
Replace motor if necessary.
■
Check mounting of motor: See
■
separate installation instructions.
Check hydraulic and electrical
■
connections of 4/3-way valve.
Check motor of 4/3-way valve.
■
Replace motor and/or 4/3-way
■
valve if required.
Check fuse for instantaneous
■
heating water heater.
Check power supply on instanta-
■
neous heating water heater and
on connections of indoor unit.
Check power cables.
■
Check instantaneous heating wa-
■
ter heater. Replace if required.
Check fuse for instantaneous
■
heating water heater.
Check power supply on instanta-
■
neous heating water heater and
on connections of indoor unit.
Check power cables.
■
Check instantaneous heating wa-
■
ter heater. Replace if required.
105