Vaillant geoTHERM VWS Installation Instructions Manual page 73

Fault code Error text/description
27 Coolant pressure too high
The integrated high pressure
switch 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 the
range
If the error occurs twice in a row
the heat pump cannot be started
until after 60 min. at the earliest.
Table 10.3 Temporary malfunctions (cont.)
Installation instructions geoTHERM VWS 0020046310_01
Troubleshooting and diagnosis 10
Possible cause
Heat consuming side using too little heat. Possible causes:
Air in the heating system.
Defective heating pump or pump
output 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
temperature falls below the outside
temp. switch-off limit! The control
system checks if heating operation is
required.
Domestic hot water cylinder with too
low a power input installed.
Existing dirt strainers clogged or
incorrectly dimensioned.
Stop valves closed.
Coolant flow rate too low (e.g.
thermal expansion valve TEV
incorrectly adjusted or defective).
Heat source providing too little heat. Possible causes:
Air in the heat source circuit.
Brine pump defective or pump output
has decreased.
The flow in some circuits is not
constant. Recognisable by different
degrees of icing on individual brine
circuits.
Existing dirt strainers clogged or
incorrectly dimensioned.
Not all the required stop valves are
open.
Coolant flow rate too low (e.g.
thermal 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.
Bleed the heat source 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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