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

EA exists only on Viessmann boilers with a Lambda Pro combustion controller under a Vitotronic control unit — the Vitodens 200-W B2HA and B2HB, the 222-F B2TA and the 242-F B2UA. No Vitodens 100-W, 111-W or 050-W has it. Lambda Pro sets the gas–air ratio by measuring the ionisation current at the flame rather than by a fixed gas valve setting, and it recalibrates itself periodically; the E-series codes E1, E2, E3, E7, E8, EA, Eb and EC are all that calibration going wrong in one way or another. EA in the 2015 B2HA edition is "Burner in a fault state — Ionisation current outside permissible range during calibration (excessive deviation from previous level)" with the measures "Check flue system; remedy flue gas recirculation if required. In open flue operation, prevent high incidence of dust in the combustion air. Press reset button R. Following several unsuccessful reset attempts, replace the coding card and press reset button R." The 2019 B2HB edition narrows the cause to "Ionisation current too low during calibration. Difference compared to previous value not plausible." and adds the ionisation electrode and its cable, loose plug-in connections, dust from building work, condensate backup, and a note that deposits on the electrodes indicate foreign bodies in the combustion air — laundry detergents, cleaning agents, toiletries.

That list is why this is a danger page with no householder steps: the controller is telling you that combustion is not what it was last time, and the causes it lists are a flue recirculating its own exhaust, an electrode that can no longer prove the flame, or contaminated combustion air. The reset is the R key on the Vitotronic control unit, once; Viessmann themselves say that after several unsuccessful resets the coding card is replaced, which is a contractor's decision. This page previously said Viessmann published nothing on EA and reported third-party readings of it as ionisation current too high or flow rate too low; those are E1 and E2 respectively, and the row above is Viessmann's own. On the 2020-on E3-platform 200-W B2HF and the numeric-table 100-W the equivalent rows are F.376 and F.464 (ionisation current differential compared to previous value not plausible).