NATE Heat Pump Service study plan

Diagram a split-system heat pump refrigerant circuit from memory, labeling compressor, reversing valve, both metering devices, indoor and outdoor coils, and accumulator or receiver, then verify against a service manual

Explain the reversing valve's four ports and state which port is pressurized in heating versus cooling, using a sketch you draw yourself

Distinguish the roles of suction line accumulator, filter-drier, and liquid-line bi-flow drier, and state where each belongs in a heat pump versus a straight-cool system

List the sequence of refrigerant state changes (pressure, temperature, phase) at six points around the circuit for both heating and cooling mode

Identify the function of auxiliary and emergency heat strips and explain when each is energized

Size and select a heat pump by performing a room-by-room load estimate using a manual J-style worksheet or approved app, documenting outdoor design temperature and indoor setpoint

Verify that the selected unit's capacity at design outdoor temperature meets the calculated load, and write the balance-point reasoning

Lay out line-set routing, condensate management, and pad or wall-bracket placement on a sketch of a representative install

State clearance requirements for outdoor unit airflow, service access, and snow/defrost rise, and justify each from manufacturer literature

Assemble a pre-installation checklist covering electrical supply, disconnect, breaker sizing, and permit/inspection items

Demonstrate brazing or flaring and torque procedures for line-set connections, including nitrogen purge and leak-test pressurization steps

Perform and document evacuation to a target micron level, including a standing vacuum decay test and the pass/fail criteria you apply

Wire a low-voltage control circuit from thermostat through indoor and outdoor boards, tracing each conductor's function on a labeled terminal map

Commission airflow by measuring external static pressure and setting blower speed to the selected tonnage and static target

Record startup measurements (ambient, supply and return dry-bulb, suction and liquid pressures, superheat or subcooling) on a commissioning sheet

Trace a defrost control board's inputs and outputs, naming the coil sensor, ambient sensor, demand signal, and reversing-valve and aux-heat outputs

Explain time-temperature versus demand defrost logic and predict board behavior at three different coil and ambient sensor conditions

Test a defrost termination sensor's resistance at two temperatures and compare to the manufacturer's resistance table

Interpret a low-voltage schematic and a ladder diagram of the same heat pump, matching five components between the two representations

Diagnose an open safety or limit in the control chain using a meter and a sequence-of-operation checklist

Build a fault tree for 'heat pump runs but does not heat' with at least eight branches and the measurement that confirms or eliminates each

Practice diagnosing three simulated electrical faults (open contactor coil, failed capacitor, bad defrost sensor) and record the meter readings that isolate each

Verify capacitor microfarad values against nameplate tolerance and state the replacement rule you follow

Check reversing valve solenoid operation and describe the pressure behavior expected when the valve fails to shift

Explain compressor protection devices (internal overload, high-pressure and low-pressure switches) and how each presents as a no-cool or no-heat call

Diagnose airflow-related complaints by measuring static pressure, temperature rise, and delta-T across the coil, and correlate readings with a duct restriction

Distinguish refrigerant undercharge from a restricted metering device using superheat, subcooling, and pressure-drop evidence, and write the reasoning for both cases

Evaluate a compressor's electrical and mechanical health with winding resistance, insulation resistance, and running current compared to nameplate RLA

Interpret a suction pressure and superheat pattern consistent with a stuck reversing valve and describe the confirming test

Write a customer-facing explanation of a diagnosed fault in plain language, without jargon, in under 120 words

Calculate target superheat for a fixed-orifice system using indoor wet-bulb, outdoor dry-bulb, and the manufacturer's charging chart, then compare against measured superheat

Calculate target subcooling for a TXV system and apply the weigh-in method when conditions fall outside the chart

Perform and document a weighing-scale charge adjustment, recording starting weight, added or recovered weight, and final verification reading

Measure total external static pressure and convert to airflow using the blower performance table, then state whether the result is within tolerance

Compute system efficiency indicators from measured data (delta-T, sensible heat ratio estimate) and flag when readings suggest degraded performance

Complete a full timed mock exam across all five domains and score each domain separately to identify remaining weak areas

Re-teach your three lowest-scoring domain topics by writing a one-page summary and a five-question self-quiz for each

Rehearse a complete service call verbally: from dispatch through diagnosis, repair, charge verification, and customer handoff, in under 15 minutes

Review safety practices for refrigerant handling, recovery, nitrogen use, and electrical lockout, and list the personal protective equipment required for each task

Recheck all previously missed practice items and confirm each can now be answered with the supporting reasoning stated aloud