Vaillant geoTHERM Installation Instructions Manual page 100

11 Fault diagnosis and rectification
Fault code Error text/description
27 Coolant pressure too high
Heat consumption of heating
circuit is too low.
The integrated high pressure
switch tripped at 3 MPa (30 bar)
(g).
The heat pump can start again
after a 60 minute wait at the
earliest.
11.3 Fault with temporary switch-off
100
Possible cause
Air in the heating system.
Pump output has dropped or heating
pump is faulty.
Radiator heating without hydraulic
switch or buffer tank.
Buffer tank, sensors VF1 and RF1
interchanged.
Too low a volume flow as a result of
closing individual room controllers in
an underfloor heating system. Heat-
ing mode is operated briefly after
every HW loading if the outside tem-
perature falls below the OT switch-
off threshold. The control system
checks if there is a heat demand.
Existing dirt strainers clogged or
incorrectly dimensioned.
Stop valves closed.
Coolant flow rate too low (e.g. ther-
mal expansion valve TEV incorrectly
adjusted or faulty).
For VWS/VWW 38/2 and 46/2 only:
The fault relay on the in-rush cur-
rent limiter has responded.
The red LED on the in-rush current
limiter is flashing:
2x = Incorrect phase sequence
3x = Compressor motor overcurrent
4x = Thyristor module excess tem-
perature
5x = Low voltage/phase failure
6x = Min./max. power frequency
7x = No compressor connected
Solution
> Bleed the heating system.
> Check the heating pump, and replace if nec-
essary.
> Check the heating system.
> Check the position of the sensors.
> Check the heating system.
> Clean dirt strainers.
> Open all stop valves.
> Have the coolant circuit checked. Inform the
factory customer service department.
> Check whether the green LED on the in-rush
current limiter is lit. If the green LED is not
lit, there is no power supply or the in-rush
current limiter is faulty.
> Check the power supply and restore.
> Check the in-rush current limiter and inform
the factory customer service department if
necessary.
> VWS/VWW 38/2 and 46/2 only:
If the green LED lights up and red LED is
flashing, find the cause in the list of flash
codes above and rectify the fault, and inform
the factory customer service department if
necessary.
Installation instructions geoTHERM 0020051574_04