Technical Trade SchoolBAS-300 service-series
BAS-302
Concept reading and source route

BAS-302 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

Diagnostic contract and stop conditions

Why it matters: Troubleshooting begins by controlling risk and meaning, not by making the first available change.

Vocabulary and working scope

Complaint; assigned scope; hazards; impacts; authority; baseline; current sources; stop; rollback; restoration; communication.

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 occupied clinic AHU has an intermittent low-temperature alarm and the operator asks for an immediate reset.

Calculation: Rank candidate tests by risk, discriminatory value, elapsed time, disruption, reversibility, and restoration effort.

Retrieval prompts

Module 2

Normal operation and system boundary

Why it matters: Actual behavior cannot be called abnormal until expected behavior is sourced for the current mode and conditions.

Vocabulary and working scope

Current sequence; mode; schedule; setpoints; state; equipment boundary; upstream/downstream systems; environment; load; responsibility.

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 VAV damper is nearly closed during heating, and a technician assumes the actuator is failed.

Calculation: Calculate expected state from supplied schedule, mode, deadband, load, and sequence conditions.

Retrieval prompts

Module 3

Complaint, symptom, evidence, cause, and correction

Why it matters: A cause explains the mechanism that produced the evidence; a component name alone usually does not.

Vocabulary and working scope

Definitions; observation conditions; evidence quality; inference; mechanism; component; contributing factor; correction; verification.

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 graphic says supply fan failure, the fan is audible, and current proof is off.

Calculation: Create a claim-evidence table and score support, contradiction, and unknown status for each statement.

Retrieval prompts

Module 4

Causal chains and last proven link

Why it matters: Diagnose at the evidence boundary: command is not output, output is not action, action is not proof, and proof is not process result.

Vocabulary and working scope

Source; command; output; interface; action; proof; process; data path; time; external interactions; responsibility path.

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 valve command and position both change, but coil discharge temperature does not respond.

Calculation: Compare expected and observed values at each link and identify the first statistically or physically meaningful divergence.

Retrieval prompts

Module 5

Hypotheses, contradictions, and falsifiability

Why it matters: A useful hypothesis predicts evidence that differs from competing explanations and can be rejected by a safe test.

Vocabulary and working scope

Mechanism-based hypotheses; supporting evidence; contradictory evidence; required assumptions; confidence; alternative explanation; red herring.

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

Zone temperature oscillates after a sensor was replaced; possible causes include tuning, location, scaling, and real load cycling.

Calculation: Use a hypothesis matrix to count unique predictions, contradictions, assumptions, and unresolved evidence.

Retrieval prompts

Module 6

Discriminating tests and half-splitting

Why it matters: The best next test is not the easiest reading; it is the safe authorized test that most reduces uncertainty.

Vocabulary and working scope

Information gain; safe access; test point; branch isolation; reversible manipulation; expected alternatives; instrument/reference; abort; restore.

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 AI is wrong at the front end; the field reference, raw controller value, and network object can be compared.

Calculation: Estimate test value as information gained divided by combined risk, disruption, time, and restoration cost.

Retrieval prompts

Module 7

Baseline, trends, time, and intermittent faults

Why it matters: Trend interval must be faster than the event being diagnosed and all compared clocks must share a known time basis.

Vocabulary and working scope

Sampling; timestamps; clock offset; mode; load; weather; occupancy; event logs; COV; gaps; aliasing; trigger capture; recurrence.

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 proof drops for ten seconds once per day, but the existing trend records every fifteen minutes.

Calculation: Compare event duration to sampling interval; calculate clock offset and minimum capture rate for the supplied case.

Retrieval prompts

Module 8

One-change control and change log

Why it matters: Multiple simultaneous changes may restore operation while destroying the evidence needed to know why.

Vocabulary and working scope

As-found; one variable; expected result; witness; temporary state; version; backup; rollback; observed effect; collateral effect.

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 technician changes PID gains, sensor offset, and setpoint before waiting for the system response.

Calculation: Calculate elapsed stabilization time from the supplied time constant and compare before/after windows under equivalent conditions.

Retrieval prompts

Module 9

Root cause, contributing factors, and correction

Why it matters: A root-cause statement must account for the evidence and survive a changed-condition verification.

Vocabulary and working scope

Mechanism; primary cause; secondary defect; contributing conditions; correction owner; affected modes; recurrence; changed-case test.

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 scaled sensor caused a false low-static alarm while an unrelated dirty filter increased fan demand.

Calculation: Reconcile evidence explained by the primary cause, secondary defect, and remaining unknowns; none may be double-counted.

Retrieval prompts

Module 10

Verification, restoration, and defensible handoff

Why it matters: A repair is not verified by disappearance of one symptom; test the causal path and affected operating cases.

Vocabulary and working scope

Affected-mode retest; before/after; alarm/safety; temporary-state register; access closure; as-left; unknowns; follow-up; customer-ready explanation.

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 alarm clears after a controller restart, but no causal evidence was preserved and the override register is incomplete.

Calculation: Reconcile every temporary state and required test; critical restoration failures force remediation regardless of average score.

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.