Viessmann VITODENS Operating Instructions Manual page 48

What to do if...
ã flashes and "Fault" is displayed
Cause
Heating system fault
ë flashes and "Service" is displayed
Cause
The time for a service, as specified by
your heating contractor, has arrived.
"Controls locked out" is displayed
Cause
Control was blocked by your heating con-
tractor.
"External hook-up" is displayed
Cause
The operating program set at the control
unit was changed by an external device,
e.g. EA1 extension.
"External program" is displayed
Cause
The operating program set at the control
unit was changed over by the Vitocom
communication interface.
48
Remedy
Proceed as described on page 40.
Remedy
Proceed as described on page 39.
Remedy
Your heating contractor can lift this
block.
Remedy
No measures required
Remedy
You can change the operating program.