AHU not holding static — floor losing air with the fan near max.

Trigger, action plan, and escalation criteria.

Related metric

ahu_fan_vfd_performance

Trigger

worst_case_box saturated_open AND duct_static < static_setpoint AND fan_speed ≥ fan_near_max, sustained over occupied hours

Value drivers

Customer experience Energy savings

Preconditions

The AHU static-pressure-reset sequence and the boxes feeding it confirmed before reporting; the worst-case box per AHU identified at onboarding as the terminal the reset should track; the fan's normal modulating range recorded so a near-max condition is detectable and distinct from a healthy modulating fan.

Human role

Scales by tier — at Essential the customer sees the worst-case box and the static gap and adjusts the reset themselves; at Managed, Keedian Ops triages whether the cause is the reset, the fan, or a restriction and dispatches; at Optimized, Keedian drives the static-pressure reset so the fan follows the worst-case box within authority, with an audit trail. A failed-open damper or a fan-side mechanical fault is referred for a scoped visit.

Action plan

(1) Read static against the reset and the fan, not in isolation — a floor short of air with the reset capped below what the worst-case box calls for is a reset finding; the same shortfall with the reset already maxed and the fan near its ceiling is a capacity finding. (2) Confirm the condition is sustained over occupied hours — the worst-case box pinned open, or the count of saturated-open boxes on the AHU crossing its limit — not a single interval or a morning ramp. (3) Place the cause: a static setpoint or reset ceiling set too low (raise or uncap the reset), a fan at its capacity ceiling or degrading (a fan-side scope), or a duct/damper restriction on the run to the starved boxes. (4) Tiered response: at Essential surface the worst-case box and the reset gap; at Managed triage and dispatch; at Optimized command the static-pressure reset to follow the worst-case box within authority, with an audit trail, and refer a failed-open damper or a fan-side mechanical fault for a field visit.

Escalation

(1) Many boxes on one AHU saturating open together while the fan runs near max → the air handler is starving the floor; escalate before comfort is lost across the zones it serves. (2) An AHU whose worst-case box stays pinned open month over month with the reset maxed → a fan-capacity or duct review candidate for the MBR rather than a repeated reset tweak. (3) A floor losing air with the fan near max on a hot afternoon → direct action before whole-floor comfort loss and the fan-energy waste compound.

Prevention

(1) Confirm the static-reset sequence and the worst-case box per AHU before arming the alarm, so a correctly parked box is not read as a shortfall. (2) Alert on the worst-case box pinned open and on the count of saturated boxes per AHU, weighted to sustained occupied-hours excursions, and trend both against the fan's speed and the reset ceiling so a capped reset or a capacity ceiling is visible as the cause. (3) Keep a per-AHU static-and-saturation log so a floor whose load has outgrown its air handler is visible over time as a capacity conversation, not a recurring alarm.