Vaillant geoTHERM VWS Series Installation Instructions Manual page 71

Fault code Error text/description
27 Coolant pressure too high
The integral high pressure switch
has tripped at 30 bar (g).
The heat pump can start again
after a 60 minute wait at the
earliest.
28 Coolant pressure too low
The integral low pressure switch
has tripped at 1,25 bar (g).
29 Coolant pressure outside speci-
fied range
If the error occurs twice in suc-
cession, the heat pump can start
again after a 60 minute wait at
the earliest.
Table 10.3 Temporary malfunctions (cont.)
Installation instructions geoTHERM VWS/VWW 0020057444_01
Troubleshooting and diagnostics 10
Possible cause
Heat consuming side using too little heat. Possible causes:
Air in the heating system.
Defective heating pump or pump out-
put has reduced.
Radiator heating without low loss
header or buffer cylinder.
Buffer cylinder, sensors VF1 and RF1
interchanged.
Too low a volume flow as a result of
closing individual room controllers in
an underfloor heating system. Brief
heating operation occurs after every
DHW charge if the outside tempera-
ture falls below the outside temp.
switch-off limit! The control system
checks if heating operation is re-
quired.
Domestic hot water cylinder with too
low a power input installed.
Existing dirt strainers clogged or in-
correctly dimensioned.
Stop valves closed.
Coolant flow rate too low (e.g. ther-
mal expansion valve TEV incorrectly
adjusted or defective).
Heat source providing too little heat. Possible causes:
(VWS only) Air in heat source circuit. Bleed the heat source circuit.
(VWS only) Brine pump defective or
pump output has reduced.
(VWS only) Not all circuits are circu-
lating equally. Recognisable by differ-
ent degrees of icing on individual
brine circuits.
Existing dirt strainers clogged or in-
correctly dimensioned.
Not all the required stop valves are
open.
Coolant flow rate too low (e.g. ther-
mal expansion valve TEV incorrectly
adjusted or defective).
Coolant pressure too high or too low,
all above-mentioned causes possible
Errors (27 and 28).
Remedy
Bleed the heating system.
Check pump, replace if necessary.
Check the system.
Check the sensor positions.
Check the system.
Check power input.
Clean dirt strainers.
Open all stop valves.
Check coolant circuit.
Check brine pump.
Adjust the brine circuits.
Clean dirt strainers.
Open all stop valves.
Check coolant circuit.
See Errors 27 and 28.
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