v0.1 · draft 60 of 60 chapters complete

HVAC Electrical
Troubleshooting

A field manual for the 75% of service calls that aren't pipe-and-water. Controls diagnosis, DC theory, and sequence-of-operation thinking — for hydronic boilers, steam boilers, forced-air furnaces, and split-system A/C.

Start with the sample chapter Read from chapter 01

Contents

Eight parts, sixty chapters

The first three parts are the foundation — electrical theory, DC-specific applications, and the meters. Parts four through seven are the job itself: how systems work, what their parts do, and the decision trees that solve service calls. Part eight keeps you alive.

  1. Part 01

    Electrical Foundations

    The minimum viable theory to stop guessing and start measuring.

    1. 01 Why Electricity Matters on an HVAC Call ✓
    2. 02 Voltage, Current, Resistance ✓
    3. 03 Ohm's Law in Practice ✓
    4. 04 AC vs DC — And Why HVAC Uses Both ✓
    5. 05 Series vs Parallel Circuits ✓
    6. 06 Reading Schematics & Ladder Diagrams ✓
    7. 07 Wire Gauge, Color Codes & Connections ✓
  2. Part 02

    DC Theory, HVAC-Specific

    Where DC actually shows up — thermocouples, thermopiles, flame rectification, 0–10V modulation, and thermistor sensing.

    1. 08 DC Basics & Where HVAC Uses It ✓
    2. 09 Thermocouples & Millivolt Systems ✓
    3. 10 Thermopiles & Self-Powered Gas Valves ✓
    4. 11 Flame Rectification — The Big One ✓
    5. 12 0–10V DC Modulation ✓
    6. 13 Thermistors & NTC Sensors ✓
    7. 14 4–20 mA Current Loops ✓
  3. Part 03

    Test Equipment

    The meters, probes, and tools that turn you from a parts-changer into a diagnostician.

    1. 15 The Digital Multimeter — Every Setting Explained ✓
    2. 16 Clamp Meters — When to Use One ✓
    3. 17 Microamp Measurement for Flame Signal ✓
    4. 18 Manometer Basics ✓
    5. 19 Combustion Analyzer Overview ✓
    6. 20 Meter Safety & CAT Ratings ✓
  4. Part 04

    Control Systems & Sequence of Operation

    If you can walk the SOO, you can diagnose any system. This is the whole job.

    1. 21 The 24V Control Circuit — The Heart of It All ✓
    2. 22 Transformers: Sizing, Grounding, VA ✓
    3. 23 Hydronic Boiler Sequence of Operation ✓
    4. 24 Steam Boiler Sequence of Operation ✓
    5. 25 Forced Hot Air Furnace Sequence of Operation ✓
    6. 26 Air Conditioning Sequence of Operation ✓
    7. 27 Heat Pump Sequence of Operation ✓
    8. 28 Zoning Systems ✓
  5. Part 05

    Components — Deep Dive

    A reference for the parts you'll touch on every call. What they do, how to test them, common failure modes.

    1. 29 Thermostats — Mechanical to Smart ✓
    2. 30 Aquastats & Operating Controls ✓
    3. 31 Gas Valves ✓
    4. 32 Ignition Modules & HSIs ✓
    5. 33 Flame Sensors ✓
    6. 34 Pressure Switches ✓
    7. 35 Limit Switches — High Limit, Rollout, Flame Rollout ✓
    8. 36 Low Water Cutoffs ✓
    9. 37 Relays, Contactors & Sequencers ✓
    10. 38 Circulators (Electrical Side) ✓
    11. 39 Blower Motors — PSC, X13, ECM ✓
    12. 40 Compressors & Contactors ✓
    13. 41 Capacitors — Run, Start, Dual-Run ✓
    14. 42 Defrost Boards ✓
    15. 43 Zone Valves & End Switches ✓
    16. 44 Reversing Valves (Heat Pumps) ✓
  6. Part 06

    Diagnostic Methodology

    The mindset and techniques that separate a parts-changer from a diagnostician.

    1. 45 The Diagnostic Mindset ✓
    2. 46 'Where Did the SOO Break?' — The Universal Framework ✓
    3. 47 Voltage Drop Testing ✓
    4. 48 Component Isolation Technique ✓
    5. 49 Intermittent Fault Hunting ✓
    6. 50 When to Use a Jumper (and When Not To) ✓
  7. Part 07

    Troubleshooting Flowcharts

    Clickable decision trees for the most common no-heat, no-cool, and fault-code calls across every system type.

    1. 51 Hydronic Boiler Flowcharts ✓
    2. 52 Steam Boiler Flowcharts ✓
    3. 53 Forced Air Furnace Flowcharts ✓
    4. 54 Air Conditioning Flowcharts ✓
    5. 55 Heat Pump Flowcharts ✓
  8. Part 08

    Safety

    Not the chapter to skip. Electrical work kills people every year. This keeps you not one of them.

    1. 56 Lockout / Tagout for HVAC ✓
    2. 57 PPE for Electrical Work ✓
    3. 58 Working on Energized Equipment ✓
    4. 59 The 'Stop and Call' Decision Tree ✓
    5. 60 Documentation & Callback Prevention ✓