BAS-402 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
A sequence is an executable contract; missing conditions and conflicts are documented and resolved before code creates an accidental design decision.
Case overlay
The sequence requires economizer cooling, the equipment submittal limits damper travel, and the points list omits mixed-air temperature.
Calculation/evidence callout: Count and reconcile requirement statements against implemented, tested, deferred, blocked, and unresolved items.
Normal-rule anchor
Every mode needs explicit priority, entry, action, exit, indication, timeout, and restart behavior; otherwise two valid conditions can produce an undefined state.
Case overlay
Warm-up and smoke shutdown become true together during a controller restart.
Calculation/evidence callout: Enumerate mode combinations, verify one effective state, and calculate timeouts and minimum dwell periods.
Normal-rule anchor
Software may respond to a listed or field safety but must not be represented as replacing required hardware, approved interface, or qualified testing.
Case overlay
A supply fan command is on, proof fails after delay, the VFD reports run, and a smoke contact changes state.
Calculation/evidence callout: Calculate proof delay, retry window, post-run, and maximum time to safe state; reconcile command, drive, proof, and process evidence.
Normal-rule anchor
The program must expose both requested and effective setpoint and identify every limit, reset, override, and fallback that can change it.
Case overlay
A duct-static setpoint rises despite low damper requests because stale zone requests continue to trim the loop.
Calculation/evidence callout: Calculate reset slope, response step, request persistence, rate limit, and bounded effective setpoint.
Normal-rule anchor
Terminal logic must match the physical terminal and central-system strategy; adding airflow reference to hybrid VVT improves evidence but does not turn one central heating/cooling source into independent zone heating and cooling.
Case overlay
A rooftop unit serves four zones using programmable VAV-class controllers, crossflow pickup tubes, and a hybrid Carrier/Trane-inspired VVT strategy.
Calculation/evidence callout: Calculate airflow setpoints, percent design flow, heating/cooling demand, damper bounds, and central-mode vote or request thresholds.
Normal-rule anchor
Reset responds to persistent valid demand and sheds stale or failed requests; it never substitutes for proper sensor location, airflow setup, or fan safety.
Case overlay
One VAV remains at 100% damper because of a failed airflow pickup and drives the AHU static setpoint to maximum.
Calculation/evidence callout: Calculate static reset steps, request persistence, SAT reset, fan tracking offset, and response/settling acceptance.
Normal-rule anchor
Economizer and ventilation logic must distinguish minimum ventilation from free cooling and must define sensor validity, lockouts, integrated cooling, damper proof, and safe low-temperature response.
Case overlay
Outdoor air is cool but humid, mixed-air temperature is unreliable, and the return fan is below its minimum speed.
Calculation/evidence callout: Calculate mixed-air temperature estimate, outdoor-air fraction where measurements permit, high-limit decision, ventilation setpoint, and low-limit response timing.
Normal-rule anchor
Plant efficiency logic cannot violate manufacturer minimum flow, anti-recycle, safeties, or project staging authority.
Case overlay
The lead pump fails proof during low load while the standby pump is unavailable and the chiller requires minimum evaporator flow.
Calculation/evidence callout: Calculate load fraction, stage thresholds, run-hour rotation, minimum flow margin, differential-pressure reset, and retry timing.
Normal-rule anchor
Guideline 36 is a source of uniform sequence intent, not permission to ignore adopted project requirements, equipment limits, or documented deviations.
Case overlay
A project specifies a custom VAV sequence but also references Guideline 36 for trim-and-respond and fault behavior.
Calculation/evidence callout: Build a clause-to-code/test matrix and calculate request thresholds, persistence, suppression, and bounded reset behavior.
Normal-rule anchor
A program is not complete when it compiles; it is complete when approved intent is traceable, critical cases pass, deployment is controlled, and restoration is proven.
Case overlay
The offline simulation passes, but the field controller has a different firmware revision and one unavailable function block.
Calculation/evidence callout: Reconcile requirements and tests, compare versions/checksums, calculate response tolerances, and prove rollback within the approved window.