B-01 gas boiler · natural draft → chimney M D-01 motorized damper · 200 mm ZS-01 K-1 relay (NC) C 24 V PLC hvac-pi GPIO 17 → /data/dashboard.json SYSTEM STATUS DAMPER — HEATER — SINCE — RUNTIME TODAY — CYCLES TODAY — 24H RUN / CYCLES — DUTY · LONGEST OPEN — NOTES 1. DAMPER STATE DERIVED FROM GPIO 17 ON hvac-pi. 2. HIGH (1) = DAMPER OPEN / HEATER RUNNING. 3. LOW (0) = DAMPER CLOSED / HEATER OFF. 4. DASHBOARD REGEN INTERVAL: 60 s. 5. SIGNAL PATH: hvac-pi → sync → /data/*.json. 6. TIMES SHOWN IN BROWSER LOCAL ZONE. WATER HEATER · TT-02 SENSOR DS18B20 · 28-..784e9a NOW — 24H MIN/MAX — 24H AVG — UPDATED — Future: chimney fan auto-on when gas burner active.