HVAC Excellence Master Combustion study plan

Define stoichiometric air-fuel ratio for natural gas and propane and compute excess air from measured O2 and CO2 values on at least 10 practice problems

Explain the relationship between O2, CO2, CO, and excess air in flue gas and predict how each shifts when a burner runs lean or rich

Calculate steady-state efficiency from flue temperature, ambient temperature, and CO2 using the flue-loss method, showing each step

Distinguish complete versus incomplete combustion products and identify the fuel/air conditions that produce each

Set up and zero a combustion analyzer per manufacturer instructions, including draft, temperature, and gas sensors, and document the calibration check

Interpret a full flue-gas printout (O2, CO, CO2, stack temp, ambient, draft) and write a pass/fail judgment for each reading against common targets

Describe how CO air-free (undiluted) values are calculated and why air-free CO matters more than as-measured CO

List the health and exposure limits and symptoms associated with CO and explain why ambient CO monitoring belongs in every combustion call

Identify the categories of venting systems (natural draft, Category I through IV) and match appliance types to correct vent materials and configurations

Explain draft, spillage, and the stack effect, and describe how to test for spillage at a draft hood safely

Trace combustion air paths into a mechanical room and calculate whether openings meet typical code sizing rules

Diagnose common venting faults: blocked flue, disconnected vent connector, reversed draft, and oversized or undersized vent

Size gas piping for a sample appliance load using longest-run length and pressure drop tables, showing the calculation

Identify sediment trap, drip leg, union, shutoff valve, and regulator placement requirements on a gas train drawing

Explain manifold pressure versus supply pressure and the role of the appliance regulator

Describe combustion air requirements for confined versus unconfined spaces and the two-opening method

Verify gas supply pressure, manifold pressure, and clock the gas meter to confirm input rate on at least three appliance types

Identify components of a standing pilot, intermittent pilot, hot surface ignition, and direct spark system and explain the ignition sequence for each

Test flame sensing (thermocouple, thermopile, flame rod) and interpret microamp or millivolt readings against specifications

Diagnose common ignition faults: no spark, weak flame signal, short cycling, and rollout switch trips

Adjust a burner for target O2 and CO while monitoring stack temperature and draft, documenting before and after readings

Explain how to tune for efficiency without creating CO, including the trade-off between excess air and flue loss

Diagnose CO production causes: dirty burners, misaligned orifices, overfiring, underfiring, blocked flue, and flame impingement

Perform a combustion safety test sequence: draft, spillage, CO in flue, ambient CO, and worst-case depressurization

Review weak areas identified in prior weeks and redo missed practice problems until each is correct without notes

Practice explaining combustion, venting, gas piping, ignition, and CO safety concepts aloud in short, exam-style answers

Take a timed 60-question mixed-domain practice set and record your score by domain

Build a personal error log of every missed question with the correct concept and a one-line rule to remember

Retake the timed mixed-domain practice set and compare scores to week 7

Drill the two lowest-scoring domains with targeted review until each reaches at least 85% on a 20-question set

Recite key formulas, code limits, and safety thresholds from memory in a self-quiz

Finalize a one-page exam-day reference of formulas, limits, and test sequences