HVAC Excellence Gas Heat Certification Exam study plan

State the stoichiometric air requirement for natural gas and propane and compute excess air from a measured O2 or CO2 reading

Identify the four legs of complete combustion and predict the flue-gas signature (CO, CO2, O2, stack temperature) produced when each leg is deficient

Convert between draft units (in. w.c., Pa) and classify natural draft, Category I, III, and IV appliances by pressure and flue temperature

Explain how derate with altitude and gas heating value (Btu/ft3) affect input rating and manifold pressure targets

Size a run of Schedule 40 black iron pipe from input Btu/h, equivalent length, and specific gravity using a pipe-sizing table, and show the arithmetic

Determine required combustion air using the indoor air infiltration method and the two-permanent-opening method, and compare results

Lay out a vent connector and chimney for a Category I appliance, checking slope, rise, connector size, and common-vent rules

Describe the correct leak-test procedure and purge steps for a new or reopened gas line

Disassemble and reassemble a redundant combination gas valve, naming each internal component and its function

Calculate orifice size and manifold pressure changes needed to hit a target input rate, and verify against nameplate

Measure and clock a meter to confirm actual firing rate, correcting for altitude, heating value, and time

Identify burner types (inshot, ribbon, tubular) and diagnose flame abnormalities such as lift, flashback, yellow tipping, and rollout

Trace the sequence of a standing pilot, intermittent pilot, hot surface ignition, and direct spark system from call for heat to blower on

Test a hot surface igniter for resistance and current draw and decide whether it is in spec

Verify flame sensing by measuring microamp signal and explain why a dirty flame sensor causes short cycling

Test limit switches, rollout switches, pressure switches, and flame roll-out devices for continuity and correct trip behavior

Read a furnace wiring diagram and identify the line-voltage, low-voltage, and safety circuits by tracing from the transformer

Wire a practice board with a control board, igniter, gas valve, blower, and limit, then verify the full sequence with a meter

Explain the role of the control board's self-diagnostics and interpret a set of blink codes

Diagnose an open safety device by voltage-drop testing rather than continuity alone

Measure static pressure across the furnace and evaporator coil and compute external static pressure

Compute temperature rise from supply and return readings and compare with the nameplate range, then adjust blower speed to correct it

Perform a combustion analysis and compare measured CO, CO2, O2, and stack temperature against acceptable targets

Inspect a heat exchanger for cracks using visual, water, and combustion-analysis methods and document findings

Apply a structured diagnostic flow to six injected faults and record the measurement that isolated each one

Distinguish heat exchanger failure from venting, gas pressure, and airflow problems that mimic it

Write a customer-facing explanation of a CO safety finding and the required corrective action

Sequence a preventive-maintenance visit covering gas train, burners, venting, safeties, and airflow

Review weak areas flagged in weeks 1 through 7 using your own error log

Complete a timed 100-question practice set across all nine domains and score by domain

Re-derive from memory the combustion, pipe-sizing, and temperature-rise formulas without notes

Rehearse a verbal walkthrough of the complete sequence of operation and the safety devices that can interrupt it