Viessmann Vitotronic 200 KW2 Installation And Service Instructions Manual page 45

Faults which are not displayed at the programming unit
Boiler hot enough, but the heating circuit pumps will not run
Set the emissions test switch to h
H Pumps are running →
No pump control:
Check heating curves, set values and heating circuit pump logic, possibly
also external hook−up (control module V, solid fuel boiler, etc.) or high
DHW demand.
H Pumps are not running → H Pumps are not running →
Is plug sÖ 'live' between L and N?
No
Check fuse F2, 4 A (slow).
If the fuse has blown:
1. Pull the plugs off pumps
and mixer motors.
2. Replace the F2 fuse.
3. Reconnect devices in
sequence to determine
which one is faulty.
4. Repeat this test, if the
fuse F2 remains intact,
but the pump connection
does not go 'live'.
Possibly replace the
main PCB.
Yes
1. Check pump connection and the pump.
2. Check any additional control devices (e.g.
maximum thermostat).
Troubleshooting
(cont.)
45