Technical Trade SchoolBAS-400 developer-series
BAS-401
Concept reading and source route

BAS-401 Reading Guide

How to use this reading guide

This is the concept-review layer for a 100% online course. Read each module before its lesson, complete the retrieval prompts without looking, then use the linked authoritative sources to verify project-specific editions, requirements, and manufacturer procedures.

Online evidence is not OJL: browser simulations, document cases, and isolated remote equipment build reasoning and documentation skill; supervised field performance is recorded separately.

Module 1

Developer role, requirement hierarchy, and authority

Why it matters: A programmer implements current approved intent; code is not permission to redesign, defeat a safety, or conceal a conflict between requirements.

Vocabulary and working scope

Owner/project requirement; sequence of operation; points list; submittal; approved drawing; software standard; platform constraint; change authorization; qualified role; stop boundary.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A project sequence says the fan shall run when occupied, while the approved safety matrix adds smoke shutdown and low-temperature lockout.

Calculation: Build a requirement-coverage matrix; every shall statement maps to logic, evidence, test, owner, and status, and unresolved conflicts remain open.

Retrieval prompts

Module 2

Controller execution model and data types

Why it matters: Logic that is mathematically correct can still fail when type, scan order, initialization, task rate, stale quality, or retained state is misunderstood.

Vocabulary and working scope

Scan cycle; task; execution order; event; object; function block; program; routine; Boolean; integer; real; string; enumeration; time; date; quality; null/default; retained/nonretained value.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A one-scan pulse is consumed before a downstream block sees it, and a retained mode returns after an unexpected restart.

Calculation: Compare task period, process time constant, pulse duration, and network update rate; state whether an event can be detected and whether aliasing or stale data is likely.

Retrieval prompts

Module 3

I/O objects, variables, units, and command priority

Why it matters: Displayed command, effective command, physical output, equipment action, and process result are separate states and require separate evidence.

Vocabulary and working scope

AI; AO; BI; BO; multistate/enumerated point; UI/UO; network value; calculated value; local/global variable; present value; reliability; units; range; scaling; priority array; relinquish default; override.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A fan graphic shows AUTO and a start command, but a higher-priority value holds the BO off and the current switch remains open.

Calculation: Convert raw input to engineering units and reconcile all active priority slots, fallback value, command, proof, and process response.

Retrieval prompts

Module 4

Boolean logic, permissives, interlocks, and latches

Why it matters: Safeties and interlocks are explicit conditions with defined reset and failure behavior; burying them inside a permissive chain makes testing and diagnosis unsafe.

Vocabulary and working scope

AND; OR; NOT; XOR; truth table; permissive; interlock; inhibit; trip; seal-in/latch; set/reset; edge; proof; fail-safe state; normally open/closed meaning; positive and negative logic.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A pump request is true, but low level blocks start; after level recovers, the trip must remain latched until an authorized reset.

Calculation: Enumerate all input combinations for up to four conditions and prove that no unsafe combination can energize the command.

Retrieval prompts

Module 5

Timers, counters, schedules, and temporal logic

Why it matters: A timer must state what starts it, what resets it, whether it retains through restart, its time base, its permitted range, and why that duration is appropriate.

Vocabulary and working scope

On-delay; off-delay; minimum on/off; debounce; persistence; watchdog; elapsed timer; counter; rate limit; occupancy schedule; holiday; temporary override; expiration; time synchronization.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A compressor request chatters around a threshold, a holiday schedule is active, and a temporary occupied override has no expiration.

Calculation: Calculate elapsed time, minimum cycle interval, starts per hour, schedule overlap, and required sample/task rate with units and a reasonableness check.

Retrieval prompts

Module 6

Analog math, scaling, reset, limits, and interpolation

Why it matters: Every analog expression carries units, valid range, fallback quality, limits, and a reasonableness test; correct arithmetic on bad data is still bad control.

Vocabulary and working scope

Raw count; sensor range; linear scaling; offset; bias; span; clamp; deadband; hysteresis; average; min/max; lead selector; linear reset; interpolation; rate of change; unit conversion; plausibility.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A 0-10 V outdoor-air sensor represents -40 degF to 140 degF and drives a supply-air reset that must remain between 52 degF and 65 degF.

Calculation: Calculate slope and intercept, test 0%, 50%, and 100% input, convert units if required, and confirm output saturation and direction.

Retrieval prompts

Module 7

Feedback control, PID, tuning, and loop evidence

Why it matters: Tuning follows verified sensor, actuator, valve/damper, direction, authority, load, and sequence checks; gains cannot repair a wrong sensor, stuck final element, or unstable upstream process.

Vocabulary and working scope

Controlled variable; setpoint; error; manipulated variable; proportional band/gain; integral/reset; derivative/rate; direct/reverse acting; bias; saturation; windup; loop enable; deadband; process lag; hunting.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A discharge-air loop oscillates every eight minutes while the valve repeatedly reaches 0% and 100%, and the sensor is located downstream of mixed air.

Calculation: Determine error sign, percent span, oscillation period, settling time, overshoot, saturation time, and whether the sample interval can represent the loop.

Retrieval prompts

Module 8

Modes, states, transitions, startup, and failure behavior

Why it matters: If mode priority, transition rules, timeouts, and restart defaults are not explicit, the program contains hidden sequences that will emerge during abnormal conditions.

Vocabulary and working scope

Mode; state; state machine; entry condition; exit condition; transition; priority; timeout; startup; shutdown; warm-up; cooldown; occupied/unoccupied; fault; degraded mode; power recovery; communication loss.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

An AHU loses communication during warm-up, power cycles, and returns with a stale occupied request and a latched freeze alarm.

Calculation: Check state coverage and transition completeness; calculate timeout and restart windows and prove that every state has a safe exit or intentional latch.

Retrieval prompts

Module 9

Readable modular code, naming, comments, and reusable blocks

Why it matters: Reusable code must make variation explicit through parameters and interfaces; copy-and-paste logic that silently diverges is a maintenance defect.

Vocabulary and working scope

Single responsibility; module/interface; input/output contract; local/global scope; naming convention; comment; revision; constant; parameter; duplicate logic; function/function block; side effect; dependency.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

Eight VAV programs differ only in box size, flow limits, and reheat type, but each contains undocumented local edits.

Calculation: Compare duplicate block counts, parameter coverage, cyclomatic decision count, comment/revision completeness, and estimated review/test effort.

Retrieval prompts

Module 10

Simulation, debugging, test cases, rollback, and release

Why it matters: A successful normal case is not release evidence; critical logic must also survive negative, boundary, loss-of-proof, communication-loss, restart, and rollback tests.

Vocabulary and working scope

Offline simulation; isolated controller; watch list; breakpoint/trace where supported; test vector; expected result; boundary value; negative test; fault injection; regression; backup; download; compare; rollback; release note.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

The logic passes occupied cooling but fails when fan proof drops after start and leaves a valve command active after the test.

Calculation: Reconcile test cases planned, passed, failed, deferred, and blocked; verify checksums/versions and calculate response times against acceptance tolerances.

Retrieval prompts

Required and deeper reading

Adoption note: Standards, codes, project requirements, owner criteria, manufacturer instructions, and employer safety programs control. Confirm the adopted edition and authority before applying a numeric requirement.