NATE HVAC study plan

State, in writing, the lockout/tagout and PPE sequence for a residential service call, and name the conditions that require immediate shutdown (gas odor, CO alarm, scorched wiring, refrigerant release in a confined space).

Reproduce the vapor-compression cycle from memory, labeling compressor, condenser, metering device, and evaporator, and give the pressure/temperature state at all four points.

Solve 20 Ohm's-law and power-formula problems (E=IR, P=IE) plus five series and five parallel resistance combinations with no reference sheet.

Demonstrate on your own meter how to read AC/DC voltage, current, resistance, and capacitance, and explain what each reading proves about the circuit.

Identify the hand tools and instruments used for refrigerant recovery, evacuation, brazing, and combustion testing, and state one safety rule for each.

Measure and calculate superheat and subcooling on a running system, then decide whether the charge is correct, over, or under.

Trace refrigerant flow through a split system and match each component to its failure symptoms for a no-cool complaint.

Read a pressure-temperature chart for R-410A and R-22 and convert gauge pressure to saturation temperature without error on 10 practice points.

Diagnose 10 written fault scenarios (restriction, undercharge, dirty condenser, weak capacitor, seized compressor, failed contactor) using only gauge, amp, and temperature evidence.

Test a run capacitor and a compressor winding set with a meter and state the pass/fail criteria for each.

Measure total external static pressure on a running air handler and compare it to the equipment rating plate limit.

Calculate airflow from both temperature rise and velocity-times-area, and reconcile any difference greater than 10%.

Plot a duct run with a duct calculator, marking equivalent length for every fitting, and flag the two highest-resistance segments.

Balance a two-branch supply system by adjusting dampers until each branch is within 10% of design airflow.

Explain how return-air restrictions, filter loading, and bypass affect delivered capacity, and show the effect on a measured temperature split.

Verify combustion air and venting for a Category I appliance against the installation instructions, and document the two most common venting violations.

Measure manifold gas pressure with a manometer and clock the gas meter to compute actual input rate in Btu/h, then compare to the rating plate.

Interpret a flue-gas analyzer readout and convert it into steady-state efficiency, CO air-free, and excess air, stating pass/fail thresholds.

Sequence both a standing-pilot and a hot-surface-ignition furnace step by step, naming each safety device that must prove before the next step and the failure symptom if it does not.

Trace a 24-volt control circuit on a schematic and locate the five points where a no-heat call is most likely to break.

Explain the defrost cycle and measure the initiating and terminating conditions, stating the sensor and board inputs that drive each.

Diagnose reversing-valve, defrost-board, and auxiliary-heat failures from a described symptom set, naming the confirming measurement for each.

Compare the charging method used in heating mode (weigh-in or approach) with the method used in cooling mode, and state why subcooling alone can mislead.

Compute the balance point and economic balance point from a capacity table and a heating-load estimate, and explain what the numbers tell a homeowner.

List the airflow and refrigerant-charge differences that make a heat pump install fail a commissioning check.

Set up an oil burner end to end: electrode gap and position, nozzle selection, pump pressure, and a combustion test targeting a smoke number of 0 to 1 with acceptable CO2.

Trace oil from tank to nozzle and diagnose a no-heat call across the pump, filter, nozzle, transformer, and primary control.

Calculate flow rate, head, and temperature drop for a hydronic loop and select a circulator that meets the requirement.

Set boiler aquastats, high limit, and low-water cutoff, and explain what each control protects and how to prove it works.

Purge air from a hydronic loop and identify the three symptoms of a system still carrying air or a fouled circulator.

Distinguish light commercial rooftop units from residential split systems across voltage, control, economizer, and ventilation requirements, and list the extra checks a commissioning visit adds.

Set up and test an economizer for changeover, minimum position, and enthalpy control, and identify the two most common economizer failure modes.

Sequence the refrigeration cycle of a medium-temperature commercial system and identify the function and failure symptoms of the receiver, liquid-line drier, sight glass, and head-pressure control.

Check superheat at the evaporator and subcooling at the condenser on a commercial system and determine whether the TXV or the charge is at fault.

Explain pump-down, defrost termination, and low-ambient control strategies and state which systems require each.

Cover the light commercial refrigeration objectives: walk-in and reach-in box loading, evaporator superheat, defrost scheduling, and product-temperature verification.

Complete two timed 100-question practice exams that mix all ten domains and log every missed question with its cause (knowledge gap, misread, or math error).

Re-drill only the missed-question topics until each is answered correctly twice in a row.

Recite the safety shutdown criteria, the superheat/subcooling decision rules, and the combustion-test targets from memory without notes.