Whether the supply (and return) fan and its variable-frequency drive deliver the airflow and static the floor needs at the fan speed and power they should — speed and power read against the air actually moved. A fan running fast and drawing power for little airflow signals a slipping belt, a fouled wheel, a failing bearing, or a VFD fault; a VFD in bypass or faulted removes the reset's ability to save energy. The health-and-efficiency signal for the AHU's largest moving part.
How efficiently and reliably the air handler's fan and its variable-frequency drive move air — the fan speed and electrical power read against the airflow and static the fan actually delivers, plus the VFD's own state (modulating, in bypass, or faulted). It is an equipment-health and efficiency signal for the AHU's largest moving part, distinct from duct static (the control target) — the fan is the machine that meets that target.
The core read is power and speed against work done — the fan's kW and percent speed compared with the airflow and static it delivers, so a fan drawing more power or running faster to move the same air is flagged as degrading.
The VFD state is scored alongside: a drive in bypass or faulted is running the fan at full speed regardless of the static reset, which both wastes energy and removes the reset's control authority — a distinct finding from a mechanically degrading fan.
Degradation separates by signature: a gradual rise in power-for-airflow points to a fouling wheel or a slipping belt; a step change points to a belt failure or a VFD event; abnormal vibration or bearing signals (where instrumented) point to a bearing on its way out — read the pattern before scoping.
| Range | Classification | Interpretation |
|---|---|---|
| Power and speed in line with airflow and static delivered; VFD modulating | Expected — healthy fan | The fan moves the floor's air at the expected power and the drive is following the reset — no action. |
| Rising power-for-airflow, or the VFD running near max to hold static | Degrading or capacity-limited — monitor | The fan works harder than expected for the air moved, or is near its ceiling; scope belt, wheel, or capacity before it fails or starves the floor. |
| VFD in bypass/faulted, or a step change in power-for-airflow | Fault — investigate | The drive has lost modulation or the fan has a mechanical fault; the reset cannot save energy and a failure may be imminent — scope the AHU. |
Reference behavior only, not fixed absolutes — a fan's expected power-for-airflow depends on its size, its duct system, and its operating point. Calibrate against the fan's own commissioned curve before alerting, and confirm the airflow and power signals are valid so a sensor fault is not read as degradation.
There is no universal fan-efficiency number — the target is a fan whose power-for-airflow tracks its commissioned curve with the VFD modulating to the static reset. Calibrate the degradation threshold per fan against its own baseline; a VFD in bypass or faulted is a finding regardless of the efficiency figure.
The table below shows how moving AHU Fan, Static & Filter Performance impacts each customer value driver the product is designed to improve — the metric page explains the mechanism; the product pages express the magnitude.
| Value driver | Impact strength | How AHU Fan, Static & Filter Performance moves this lever |
|---|---|---|
| Energy savings | Direct, primary | The supply fan is one of the largest continuous electrical loads on an all-air floor, and its energy is only recoverable while the VFD modulates to the static reset — a drive in bypass or a fouling fan spends fan energy the reset should have saved. Catching degradation and bypass early protects the fan-energy savings the whole add-on depends on. Magnitude is expected (pending validation) — offices have no named Keedian reference deployment yet. |
| Asset lifespan | Direct | A slipping belt, a fouling wheel, or a failing bearing shows first as a rising power-for-airflow or a vibration signature — long before the fan fails. Flagging it turns an unplanned fan failure that shuts down a floor into a planned belt, wheel, or bearing service. |
| Avoided truck rolls | Indirect, leading indicator | A VFD fault or a developing mechanical problem caught remotely is scoped into one planned visit with the right parts, rather than an emergency call after the floor loses air — and a bypass caught remotely is often a reset a technician can clear without a return trip. |
The table below summarizes the alarms that fire directly from AHU Fan, Static & Filter Performance. Each row links to the full operational detail (trigger, preconditions, action plan, human role, escalation, prevention) in the SOPs catalog.
| Alarm | Description | Severity | Tier | AI executes? | Value drivers | SOP |
|---|---|---|---|---|---|---|
| AHU not holding static — floor losing air with the fan near max | The air handler cannot hold the duct static its VAV boxes are calling for — the worst-case box stays pinned open, or several boxes saturate open at once, while the supply fan runs at or near maximum speed. The floor is running out of air even though no single box has failed: a static setpoint or reset capped below demand, a fan at its capacity ceiling, or a system restriction. | High | Essential | Hybrid | Customer experience · Energy savings | Open SOP → |
| AHU fan drive in bypass or faulted — modulation and reset authority lost | The supply-fan variable-frequency drive is running in bypass or has faulted — the fan runs at full speed regardless of what the static-pressure reset is asking for. Both an energy finding (the reset can no longer save fan energy) and a control-authority finding (the fan can no longer follow the floor's demand): a drive fault, a manual bypass left in place after service, or a tripped protection. | Medium | Essential | Hybrid | Energy savings · Asset lifespan · Avoided truck rolls | Open SOP → |
| AHU filter loading high — pressure drop past the change threshold | The pressure drop across the air handler's filter bank has risen past its change threshold — the filters are loaded and the fan is working harder to push the same air through them. Left alone it raises fan energy, erodes the fan's ability to hold static for the floor, and eventually lets the filter bypass; caught in time it is a planned filter change, not an emergency. | Medium | Essential | Hybrid | Energy savings · Asset lifespan | Open SOP → |
More alarms in development (single-metric): a power-for-airflow degradation trend that separates fouling from belt slip, and a bearing/vibration early-warning where instrumented. Composite AHU alarms that weigh this metric's duct-static, filter and fan-health alarms together to attribute a high fan power to its cause will appear in a future release.
The action plan for each alarm lives on its own SOP page in the SOPs catalog — with the diagnostic steps, human role, value drivers, escalation, and prevention specific to that alarm. The list below maps each alarm to its SOP.
Power-for-airflow degradation is only meaningful if the airflow and power signals are valid — a drifted airflow station or a mis-scaled power meter manufactures false degradation. Confirm the signals and compare against the fan's commissioned curve before scoping a mechanical fault, and treat a VFD bypass as a distinct, immediately actionable finding regardless of the efficiency figure.
At Essential the customer sees the fan's health and VFD state and acts themselves; at Managed, Keedian Ops runs the bypass/fault and degradation alarms, triages the signature, and dispatches; at Optimized, Keedian commands fan speed through the static-pressure reset (with an audit trail) and refers a mechanical fault — belt, wheel, bearing — or a failed VFD for a scoped field service.
Per-alarm escalation criteria live in the Escalation block of each SOP in the SOPs catalog. The patterns below are metric-level — read from the portfolio view, not from any single alarm firing.