8 Fault finding
uniSTOR GB
22
Fig. 15
The water from the cylinder is cold.
Does boiler operate?
Do external controls
function?
Remedy fault
according to boiler
instructions.
Remedy fault
according to controls
instructions.
Is 2-port valve in
correct position?
(DHW position).
Does cylinder
thermostat operate?
Replace cylinder
thermostat.
Vent heating coil of
air (H, fig. 4).
Check/replace
2-port valve.
Is operation now
OK?
Fault remedied.
NO
NO
YES
YES
NO
NO
YES
YES
YES
NO
Check/reset
Thermal cut out
8 Fault finding
Note:
Only genuine spare parts supplied by Vaillant
Limited must be used.
Fault A:
