BAS-405 Visual Aid Library
Figure-use rule
Each figure is an orientation and reasoning aid, not a project drawing. Learners must pair it with the current sequence, point list, wiring/piping documents, manufacturer instructions, and as-found evidence.
Normal-rule anchor
An alarm, trend, or schedule without an owner and defined operational purpose becomes noise, cost, or hidden risk.
Case overlay
A building has thousands of alarms, no documented response owners, and three conflicting occupancy schedules.
Calculation/evidence callout: Inventory and reconcile configured artifacts against required, owned, tested, obsolete, and exception categories.
Normal-rule anchor
An alarm is actionable information requiring a defined response; abnormal data that requires no action may belong in a trend, diagnostic, or report instead.
Case overlay
Every VAV reports a high-damper alarm during morning warm-up, but operators have no action to take.
Calculation/evidence callout: Calculate alarm rate by class, actionable percentage, standing alarms, and priority distribution against owner targets.
Normal-rule anchor
Delay and deadband are justified by process dynamics, sensor quality, consequence, and response, not selected merely to reduce alarm count.
Case overlay
A discharge-air deviation alarm chatters every minute after fan startup and remains active after the system enters unoccupied mode.
Calculation/evidence callout: Calculate deviation, persistence, delay, hysteresis, process time, and expected return-to-normal window.
Normal-rule anchor
Acknowledgement does not correct the condition; shelving and suppression are temporary governed states with reason, owner, expiry, and audit.
Case overlay
A contractor shelves a recurring chiller alarm for a week using a shared account and no expiration note.
Calculation/evidence callout: Reconcile sent, received, acknowledged, acted, returned, shelved, expired, and orphaned events with timestamps.
Normal-rule anchor
Alarm reduction preserves required detection and response; hiding symptoms without correcting logic, equipment, ownership, or process is not rationalization.
Case overlay
A network dropout generates 600 downstream point alarms in four minutes and obscures the single gateway failure.
Calculation/evidence callout: Calculate alarms per hour, flood peaks, chattering frequency, standing duration, top contributors, and reduction without loss of required coverage.
Normal-rule anchor
Trending every point at one interval is not a strategy; select values and states that trace source, decision, command, proof, process, and context.
Case overlay
The question is why zone temperature rises each afternoon, but the existing trend contains only zone temperature.
Calculation/evidence callout: Map each hypothesis to required points and calculate coverage, data age, and expected event duration.
Normal-rule anchor
Sampling must be fast enough for the process and all compared clocks must share a known time basis; rollups cannot recreate detail that was never captured.
Case overlay
A ten-second fan-proof dropout occurs daily, but proof is stored on a fifteen-minute interval and controllers differ by six minutes.
Calculation/evidence callout: Compare event duration, sample rate, COV behavior, storage estimate, clock offset, completeness, and rollup error.
Normal-rule anchor
Correlation and sequence coincidence generate hypotheses; root cause requires a mechanism and a test that distinguishes alternatives.
Case overlay
Valve command tracks temperature error, but discharge temperature does not change until twenty minutes later and outdoor temperature is falling.
Calculation/evidence callout: Calculate error, lag, rate of change, percent time saturated, cycle period, before/after difference, and uncertainty.
Normal-rule anchor
Every temporary schedule or occupancy override has a reason, owner, start, expiry, affected systems, audit, and verified release.
Case overlay
A recurring holiday exception leaves the building occupied for a weekend after daylight-saving time changes.
Calculation/evidence callout: Calculate occupied hours, exception overlap, optimum-start lead, after-hours duration/cost proxy, and expiration/release status.
Normal-rule anchor
Configuration is accepted only when operators can interpret and act, audit is preserved, critical faults remain visible, and temporary states return to normal.
Case overlay
A staged fault alarms correctly but routes to the wrong role, the trend starts after the event, and the maintenance suppression remains active.
Calculation/evidence callout: Reconcile planned/actual tests, response times, routing, trend coverage, schedule state, suppression expiry, and restoration.