Investigating an unexplained 21-minute full-power heating run on
2026-07-09 09:25 showed the HPMU event log is the one diagnostic
surface open3e never published: vitocal.259 (InfoDtcList) and
vitocal.260 (InfoDtcHistory) were absent from the poll list, so only
the VX3's counterpart (vx3.266) was ever visible.
A one-shot `{"mode":"read","data":[259,260],"addr":"0x680"}` over
open3e/cmnd confirmed both decode cleanly through the vcal codec and
are capped lists — 2 and 9 entries respectively — so the multi-frame
ISO-TP read costs little next to the 87 DIDs already polled at 30 s.
Scope note: this log records faults and info events only
(NormalOperation, LagDeviceDtcReported,
LegionellaProtectionTemperatureReached). It does not record setpoint
or operating-program changes, so it would not have attributed the
09:25 run. It is still the right place to catch recurrences of the
legionella heating-rod cycle and lag-device dropouts.
Read-only: no -w flag, no new write path.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
k.rennerandClaude Opus 4.8