Canonical public FDD taxonomy

Neutral, standards-first taxonomy for Open-FDD rule cookbooks. Names are generic semantic variables — portable across Haystack-modeled sites and generic BAS telemetry. Not tied to any vendor namespace.

Literature anchors (public)

Source	Use in this taxonomy
ASHRAE Guideline 36 AFDD addenda	AHU supervisory faults, internal variables, confirmation delays
Berkeley Lab HVAC fault taxonomy	Equipment classes, fault categories, symptom → cause mapping
Berkeley Lab FDD benchmarking datasets	Regression scenarios, expected fault signatures
PNNL AIRCx / re-tuning literature	Reset, schedule, override, performance KPI opportunities
NIST HVAC-Cx guidance	AHU/VAV commissioning checks transferable to continuous FDD
Project Haystack	Equipment tags, point semantics

Equipment classes

Class ID	Description	Example Haystack tags
`ahu`	Air handling unit	`ahu`, `airHandlingEquip`
`vav`	Variable air volume terminal	`vav`, `vavZoneEquip`
`rtu`	Rooftop unit	`rooftopUnit`
`fcu`	Fan coil unit	`fanCoilUnit`
`plant.chw`	Chilled-water plant	`chillerPlant`, `chilledWaterPlant`
`plant.hw`	Hot-water / boiler plant	`hotWaterPlant`, `boilerPlant`
`plant.tower`	Cooling tower	`coolingTower`
`hp`	Heat pump	`heatPump`
`sensor.weather`	Weather station	`weatherStation`
`site`	Whole-building / meter	`site`, `elecMeter`

Rule families (top level)

Family ID	Name	Typical symptoms
`sensor.quality`	Sensor validation	Out of range, flatline, spike, stale, mixing envelope
`control.loop`	Control loop	Hunting, setpoint tracking error, simultaneous heat/cool
`economizer`	Economizer & OA	Stuck closed, unfavorable economizing, low OA fraction
`ventilation`	Ventilation	Low OA, preheat over-conditioning, DCV miss
`schedule`	Schedule & occupancy	Unoccupied runtime, setback miss, morning warm-up fail
`reset`	Reset logic	Missing SAT/CHW/HW/DP reset, setpoint too high/low
`override`	Overrides	Persistent manual override, bypass active
`actuator.leakage`	Valve / damper leakage	Flow/temp when commanded closed
`plant.performance`	Plant performance	Low ΔT, DP miss, flow anomaly, tower approach
`terminal.vav`	VAV terminals	Comfort band, reheat, damper stuck, airflow bias
`command.status`	Command vs status	Fan/pump/damper cmd ≠ feedback
`kpi.advisory`	Performance KPI	Trim/respond, energy opportunity scoring
`safety.envelope`	Safety envelopes	GL36-style MAT/SAT/OAT consistency checks

Taxonomy path format

{family}.{equipment_class}.{rule_id}

Examples:

sensor.quality.ahu.sv_oa_range
control.loop.ahu.fc4_pid_hunting
reset.plant.chw.dp_reset_missing
schedule.vav.unoccupied_runtime
override.ahu.persistent_manual

Severity scale

Level	Label	Typical response
1	Advisory	Log, trim/respond, RCx queue
2	Warning	Operator review within 24 h
3	Fault	Work order, comfort/energy impact
4	Critical	Immediate — safety or major waste

Priority scale (implementation roadmap)

Priority	Meaning
P0	In both cookbooks today, parity verified
P1	High public-literature value — draft in v2 expansion
P2	Common RCx find — scheduled next
P3	Niche / site-specific — document pattern only

See gap matrix, parity matrix, and roadmap.