Viessmann VITOCAL 151-A Installation And Service Instructions Manual page 112

Troubleshooting
Fault messages
(cont.)
Message code System characteristics
F.996 No cooling of external coolant
buffer cylinder
F.997 No cooling of external coolant
buffer cylinder
F.998 The refrigerant circuit will not
start.
F.1009 Refrigerant circuit off
F.1010 Refrigerant circuit off
F.1011 Refrigerant circuit off
112
Cause
Short circuit, temperature
sensor of external coolant
buffer cylinder
Lead break, temperature
sensor of external coolant
buffer cylinder
Flow rate signal faulty
Fault, oil sump heater
Fault, secondary circuit
pressure sensor
Fault, high pressure sen-
sor
Measures
Check the settings in the com-
■
missioning assistant. Adjust set-
tings if required.
Check resistance value
■
(NTC 10 k ) at connection X17
Ω
of the EHCU electronics module.
Replace sensor if required.
Check the settings in the com-
■
missioning assistant. Adjust set-
tings if required.
Check resistance value
■
(NTC 10 k ) at connection X17
Ω
of the EHCU electronics module.
Replace sensor if required.
Check flow sensor. Replace if re-
■
quired.
Check CAN bus connections:
■
– CAN bus cable, indoor/outdoor
unit
– Check connection X19 on EH-
CU electronics module.
–
Check connections X4 on
HPMU electronics module.
– Check connection X5 on EH-
CU electronics module.
Isolate the system from the pow-
■
er supply. Restart the system.
If the fault persists, replace the
CAN bus cable. Replace EH-
CU electronics module if re-
quired. Replace HPMU electron-
ics module if required.
If the fault occurs repeatedly, re-
place VCMU refrigerant circuit con-
troller, internal CAN bus cable har-
ness and EHCU electronics mod-
ule.
Check oil sump heater. Check
electrical connections X4 on
VCMU refrigerant circuit controller.
Replace oil sump heater if re-
quired.
To check the sensor, measure the
voltage at the sensor or at connec-
tion X11 of the EHCU electronics
module (0 to 5 V). Replace sensor
if required.
To check the sensor, measure the
voltage at the sensor or at connec-
tion X14.1 to X14.3 of the VCMU
refrigerant circuit controller (0 to
5 V). Replace sensor if required.