Vaillant ecoTEC plus VU 446/5-5 (H-GB) Installation And Maintenance Instructions Manual page 63

Code/meaning
F.75
Pump fault/water deficiency
F.77
Accessory fault (flue non-return
flap, condensate pump, etc.)
F.83
Fault: Flow and/or return tem-
perature sensor temperature
change
F.84
Fault: Temperature difference at
the flow and return temperature
sensors
F.85
Flow and return temperature
sensors have been installed
incorrectly (inverted)
0020261389_03 ecoTEC plus Installation and maintenance instructions
Possible cause
D.149 = 6, no feedback from
the pump
D.149 = 7, incorrect pump de-
tected
D.149 = 8, flow rate at the end
of the purge programme is in-
sufficient
No feedback from the flue non-
return flap or the feedback is
incorrect
Flue non-return flap defective
No feedback from the condens-
ate pump or the feedback is in-
correct
Water deficiency
Flow NTC: No contact
Return NTC: No contact
Flow NTC installed incorrectly
Return NTC installed incorrectly
Flow/return NTC installed on
the same/incorrect pipe
Measure
1. Check the pump's cable harness.
2. Check the main PCB.
3. Check that the plugs are connected correctly.
4. Check the pump's supply voltage.
– ≥ 195 V
5. Replace the pump.
6. Replace the main PCB.
1. The detected pump is not correct for the product code;
check the product code.
2. Use the pump that has the correct article number.
1. Check whether the stopcocks and thermostatic valves are
open.
2. Check the filling pressure; purge the circuit.
– ≥ 0.15 MPa (≥ 1.50 bar)
▶
Check that the flue non-return flap works without any prob-
lems.
▶
Replace the flue non-return flap.
▶
Check that the condensate pump is working correctly.
▶
Fill the heating installation. (→ Page 35)
▶
Check whether the flow NTC is lying against the flow pipe cor-
rectly.
▶
Check whether the return NTC is lying against the return pipe
correctly.
▶
Check that the flow NTC has been installed correctly.
▶
Check that the return NTC has been installed correctly.
▶
Check that the flow and return NTCs have been installed on
the correct pipe.
63