BAS-303 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
The newest guideline or program is not automatically the project sequence; applicability and revision must be proven.
Case overlay
The approved sequence and current program disagree after an undocumented change.
Calculation/evidence callout: Reconcile clause, revision, program version, point list, and test record before deciding which difference is a fault.
Normal-rule anchor
A sequence is more than output values; entry, steady behavior, exit, and transition priority must be explicit.
Case overlay
An AHU remains in warm-up after zone temperatures satisfy the exit condition.
Calculation/evidence callout: Evaluate Boolean transition conditions and elapsed time in the stated order and priority.
Normal-rule anchor
Optimization never outranks life safety, equipment protection, or defined fallback behavior.
Case overlay
A fan restart is requested immediately after power recovery while dampers have not proven position.
Calculation/evidence callout: Calculate delay and proof windows and build a truth table for permissives, trips, fallback, and restart.
Normal-rule anchor
Deadband separates actions around a target; hysteresis and timers prevent unstable repeated switching.
Case overlay
Heating and cooling commands alternate every minute near the zone setpoint.
Calculation/evidence callout: Calculate upper/lower thresholds, elapsed persistence, minimum run/off time, and expected next transition.
Normal-rule anchor
Correct direct/reverse action and trustworthy sensors/actuators/process are verified before gain changes.
Case overlay
A cooling-valve loop drives closed when discharge temperature rises above setpoint.
Calculation/evidence callout: Calculate signed error and proportional response using the supplied controller convention; conventions must be stated.
Normal-rule anchor
A reset schedule is an equation with limits and applicability, not a line copied from another project.
Case overlay
The SAT reset calculates below the approved low limit during mild weather.
Calculation/evidence callout: Use y=y1+(x−x1)(y2−y1)/(x2−x1), then apply enable conditions and high/low clamps.
Normal-rule anchor
A high request count may represent one upstream fault or bad data; validate request identity and quality before responding.
Case overlay
Static pressure rises to maximum because several boxes generate persistent requests from failed airflow sensors.
Calculation/evidence callout: Calculate request count/severity, interval-based trim/respond steps, clamps, and time to target from supplied rules.
Normal-rule anchor
A testable sequence connects narrative requirements to specific point identities, physical observations, time, and expected results.
Case overlay
The sequence requires fan proof and airflow response, but the database contains only a fan command.
Calculation/evidence callout: Build a state/point matrix and reconcile required, available, trustworthy, and missing evidence counts.
Normal-rule anchor
A technician may diagnose a design/program deviation without gaining authority to rewrite the design.
Case overlay
A reset loop follows the current program exactly but conflicts with the approved sequence.
Calculation/evidence callout: Compare expected and actual states across identical conditions and quantify the deviation, timing, and affected modes.
Normal-rule anchor
A valid test defines initial state, manipulation, expected response, tolerance/time, evidence, result, and restoration.
Case overlay
A sequence test passes one steady state but never tests transition, failure, or restart behavior.
Calculation/evidence callout: Reconcile required vectors, executed vectors, pass/fail/blocked, retested, and restored states; critical vectors cannot be averaged away.