Technical Trade SchoolBAS-300 service-series
BAS-301
Concept reading and source route

BAS-301 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

Electrical diagnostic plan and qualification boundary

Why it matters: Low voltage is not automatically low risk, and online training does not authorize energized testing.

Vocabulary and working scope

Current one-line/schematic; voltage/system; energy source; LOTO state; qualified role; instrument category/rating; test point; expected value; arc/shock boundary; stop/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

A learner proposes to check resistance across an energized 24 Vac relay coil.

Calculation: Compare expected potential between exact test points and verify instrument range/category before measurement.

Retrieval prompts

Module 2

Control transformers, VA, and voltage drop

Why it matters: Nominal 24 Vac at the transformer does not prove adequate voltage at the energized device under load.

Vocabulary and working scope

Primary/secondary; grounding/reference; fuse; class; VA rating; inrush; connected load; conductor resistance; terminal drop; shared commons.

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

Several actuators start together and the controller reboots while open-circuit voltage appears normal.

Calculation: VA = volts×amps; percent loading = connected VA/rated VA×100; voltage-drop percent = drop/source×100.

Retrieval prompts

Module 3

Protection, fuses, safeties, and resets

Why it matters: A blown fuse or tripped safety is evidence of a condition, not permission to install a larger device or repeatedly reset.

Vocabulary and working scope

Overcurrent device; fuse class/rating; short/overload; safety control; manual/automatic reset; root-cause review; replacement authority; coordination 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 secondary fuse opens whenever a damper actuator is commanded near end of travel.

Calculation: Compare measured/supplied current to device, conductor, and protective ratings without changing specified protection.

Retrieval prompts

Module 4

Relays, SPDT/DPDT, and interposing control

Why it matters: A RIB commands the starter or VFD control input; it never switches one leg of a three-phase motor circuit.

Vocabulary and working scope

Coil; pickup/dropout; NO/NC/common; SPDT; DPDT; contact rating; isolation; suppression; RIB; fail state; control-circuit drawing.

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 proposes to place a RIB relay in phase B because the BAS output cannot carry motor current.

Calculation: Calculate coil VA/current and compare contact voltage/current/load type to the exact relay rating.

Retrieval prompts

Module 5

Series safety chains, permissives, HOA, and local control

Why it matters: A bypass may make equipment run while destroying the protection and evidence needed to diagnose the real condition.

Vocabulary and working scope

Series contacts; normal state; permissive; interlock; proof; seal-in; HOA; local/remote; emergency stop; freeze/high/low limit; fault reset.

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 fan will run in HAND but not AUTO, and one safety contact is open.

Calculation: Use source-to-load potential measurements across defined nodes to locate the voltage transition under an approved procedure.

Retrieval prompts

Module 6

Legacy pneumatic, electric, and electronic interfaces

Why it matters: Signal compatibility requires range, action, reference, power, fail state, and authority—not just matching terminal labels.

Vocabulary and working scope

3–15 psi; EP/PE transducers; pneumatic relays; two-position/floating/proportional circuits; 0–10 V; 4–20 mA; shared commons; retrofit 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 DDC AO drives an EP transducer correctly, but the pneumatic actuator does not stroke.

Calculation: Convert 0–10 V or 4–20 mA command to percent and expected 3–15 psi branch pressure using supplied linear ranges.

Retrieval prompts

Module 7

Single-phase and three-phase motor systems

Why it matters: Opening or switching one phase of a running three-phase motor is not a BAS control strategy and can damage equipment.

Vocabulary and working scope

Single-phase capacitor/start components awareness; three-phase line/load; phase sequence; imbalance; rotation; nameplate; disconnect; motor versus control circuit.

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 three-phase motor hums, current proof is present, and one phase is lost upstream.

Calculation: Use supplied phase currents to calculate percent current imbalance by the specified method and escalate unacceptable results.

Retrieval prompts

Module 8

Contactors, starters, overloads, and auxiliary contacts

Why it matters: An overload trip protects the motor circuit; repeated reset without cause review is not troubleshooting.

Vocabulary and working scope

Coil voltage; contactor; starter; overload relay; heater/electronic setting; auxiliary contact; seal-in; trip class awareness; reset; proof.

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 starter coil is energized, the contactor pulls in, and the motor does not turn.

Calculation: Compare supplied full-load current, service factor/application data, and approved overload setting; do not invent settings.

Retrieval prompts

Module 9

VFD interface, permissives, source, and faults

Why it matters: A VFD output-frequency display is not proof of motor rotation, belt condition, airflow, or correct parameterization.

Vocabulary and working scope

Line/load/DC bus boundary; run enable; speed reference; HOA/keypad/remote source; safe-off; fault relay; bypass; feedback; minimum speed; acceleration; parameter authority.

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 BAS commands 60%, but the drive remains at 30 Hz because the keypad is the active reference source.

Calculation: Convert command percent to expected reference and frequency only from the approved min/max mapping and current source.

Retrieval prompts

Module 10

Controlled diagnosis, restoration, and motor-control capstone

Why it matters: The completed diagnosis identifies mechanism, responsible role, affected protection, and zero unaccounted temporary states.

Vocabulary and working scope

Baseline; last proven link; one-change test; qualified referrals; jumper/override/HOA register; enclosure; rotation; proof; process; retest; as-left.

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 is restored after a relay change, but the VFD remains in LOCAL and the panel cover is open.

Calculation: Reconcile every test point, temporary state, mode, cover, fault, alarm, and affected-mode retest before closure.

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.