Viessmann [F4] fault codewhat it means and how to fix it

F4 is the Vitodens lockout for a burner start that produced no flame signal, and every two-character control unit from the WB1A to the B1HC prints the same row: system characteristics "Burner in a fault state", cause "No flame signal". Viessmann's list of what the contractor checks is long, and its length is the point — the ignition/ionisation electrode and its cable, the gas pressure, the gas train, ignition and ignition module, and the condensate drain. The 2011 WB1B edition adds "measure the ionisation current". Any one of those can stop the flame being seen even when gas has been released, which is why the burner control unit shuts the gas train and holds the fault rather than trying again indefinitely.

The householder side is narrower. The B1HC operating instructions give two things you may check before a reset: that the gas shut-off valve is open (and with LPG, that there is fuel), and the pressure gauge. If the fault symbol flashes and the burner does not start, Viessmann permit a single reset and then say to notify the contractor if the fault recurs, with the warning that unrectified faults can have life threatening consequences. On the WB1B, WB1C and B1HA the reset is the heating rotary selector turned to RESET for under two seconds; on the B1HC it is touching "R" for about two seconds; on the WB1A it is the lit Reset key; on the 050-W BPJD it is MODE and OK together. Two families do not use F4 at all: the 2020-on units with the numeric table report the same event as F.65 or F.361 (flame signal not present or insufficient at burner start), and the Vitotronic-controlled 200-W, 222-F and 242-F report it as EE. Each has its own page.