Viessmann B1HF Installation And Service Instructions Manual page 84

Troubleshooting
Repairs
(cont.)
Fig. 43
84
Constant green LED:
■
Pump is running without external control from the
boiler controller
■ Flashing green LED:
Pump is running with external control from the boiler
controller
Constant red LED:
■
Pump failure
Note
The pump is controlled by a PWM signal. A lead break
in the data line will not generate a fault message.
The pump is operating at 100 % of its maximum out-
put.