HVAC Excellence Employment Ready Certifications (HEERC) Overview
These study notes are designed to prepare candidates for the HVAC Excellence Employment Ready Certifications (HEERC) exam. The notes cover six core subjects: Electrical Fundamentals and Circuit Troubleshooting, Refrigeration Cycle and Thermodynamic Principles, Air Distribution and Psychrometrics, Gas Heating Systems and Combustion Analysis, Heat Pump Operation and Defrost Cycles, and System Installation, Maintenance, and EPA Compliance. Each subject includes key concepts, must-know items, clinical applications (field applications), high-yield distinctions, common pitfalls, and review tasks. The exam is typically 80 questions in 120 minutes with a pass mark of 70% (practice baseline). Candidates should verify official details with HVAC Excellence or ESCO Institute.
For Technical Conquer practice planning, this module is tracked as 80 questions over about 120 minutes with a listed pass mark of 70%. Treat those numbers as practice baselines and verify the current official format before scheduling.
How This Guide Is Organized
The sections below turn the syllabus into studyable subject blocks. Read a subject first, explain the must-know ideas without notes, then use questions, flashcards, and mind maps to test whether the knowledge holds under field-style pressure.
- Electrical Fundamentals and Circuit Troubleshooting
- Refrigeration Cycle and Thermodynamic Principles
- Air Distribution and Psychrometrics
- Gas Heating Systems and Combustion Analysis
- Heat Pump Operation and Defrost Cycles
- System Installation, Maintenance, and EPA Compliance
Exam Snapshot and Readiness Target
Format: 80 questions, 120 minutes, pass mark 70% (practice baseline; verify official)
Candidate level: Entry-level technician; Employment Ready certification
Readiness target: Demonstrate foundational knowledge in electrical, refrigeration, air distribution, gas heating, heat pumps, and installation/maintenance/EPA compliance.
Most candidates should budget at least 36+ focused study hours, then adjust upward for unfamiliar equipment, code, regulatory, commissioning, controls, or calculation-heavy content.
Electrical Fundamentals and Circuit Troubleshooting
Syllabus Focus
- Basic electrical theory (voltage, current, resistance, power)
- Series and parallel circuits
- Ohm's Law and Kirchhoff's Laws
- Electrical components (relays, contactors, capacitors, transformers)
- Troubleshooting techniques (voltage drop, continuity, component testing)
Key Notes
- Voltage is the potential difference, current is the flow of electrons, resistance opposes flow. Power (watts) = voltage × current.
- In series circuits, current is constant; voltage divides. In parallel circuits, voltage is constant; current divides.
- Ohm's Law: V = I × R. Kirchhoff's Voltage Law: sum of voltage drops equals source voltage. Kirchhoff's Current Law: sum of currents entering a node equals sum leaving.
- Capacitors store electrical energy; used for starting motors (start capacitors) and running motors (run capacitors). Start capacitors are electrolytic; run capacitors are oil-filled.
- Transformers step down voltage for control circuits (e.g., 24V from 120V or 240V). Primary side is line voltage; secondary is low voltage.
- Troubleshooting: measure voltage at load, check for voltage drop across switches/contacts, test capacitors with a multimeter (capacitance setting), check continuity of coils and windings.
Must Know
- Calculate total resistance in series (R_total = R1 + R2 + ...) and parallel (1/R_total = 1/R1 + 1/R2 + ...).
- Identify and test common components: contactor coil (24V), relay, capacitor (start/run), transformer (primary/secondary).
- Use a multimeter to measure AC/DC voltage, resistance, and capacitance safely.
- Understand wiring diagrams (schematic and ladder) to trace circuits and diagnose faults.
Field and Exam Application
- Diagnose a compressor that won't start: check voltage at contactor coil, test capacitor, verify overload protection.
- Troubleshoot a fan motor that runs slowly: measure voltage at motor, check run capacitor value, inspect for loose connections.
- Identify a shorted transformer: measure secondary voltage, check for blown fuse or tripped breaker on primary side.
High-Yield Distinctions
- Start capacitors are in series with the start winding and are removed by a centrifugal switch or relay; run capacitors are always in series with the start winding.
- A contactor is a heavy-duty relay for switching compressor and fan motors; a relay is for lower current loads.
- Voltage drop across a closed switch should be near zero; a significant drop indicates resistance (e.g., pitted contacts).
Common Pitfalls
- Confusing start and run capacitors: start capacitors have higher capacitance and are not rated for continuous duty.
- Forgetting to discharge capacitors before testing (risk of shock or meter damage).
- Misinterpreting a low voltage reading as a bad component when the issue is a poor connection or undersized wire.
Review Tasks
- Draw a simple series circuit and calculate current given voltage and resistance.
- Practice reading a ladder diagram for a basic cooling system (compressor, condenser fan, evaporator fan).
- Use a multimeter to measure voltage at a wall outlet and a 24V transformer secondary.
Refrigeration Cycle and Thermodynamic Principles
Syllabus Focus
- Basic refrigeration cycle (evaporation, compression, condensation, expansion)
- Pressure-temperature relationship
- Superheat and subcooling
- Refrigerant properties and types
- Thermodynamic laws (first and second law)
Key Notes
- The refrigeration cycle: low-pressure liquid refrigerant evaporates in the evaporator (absorbs heat), compressor raises pressure and temperature, condenser rejects heat (gas to liquid), expansion device reduces pressure and temperature.
- Pressure and temperature are directly related for a given refrigerant (saturation point). Use a P-T chart to find saturation temperature at a given pressure.
- Superheat = actual temperature of refrigerant vapor minus saturation temperature at the same pressure (measured at evaporator outlet). Subcooling = saturation temperature minus actual liquid temperature (measured at condenser outlet).
- Common refrigerants: R-410A (higher pressure, used in newer systems), R-22 (being phased out), R-134a (medium temp). Each has unique P-T characteristics.
- First law of thermodynamics: energy cannot be created or destroyed, only transferred. Second law: heat flows from hot to cold; work is required to move heat against its natural gradient.
Must Know
- Read a P-T chart for R-410A and R-22 to find saturation temperatures.
- Calculate target superheat (typically 8-12°F for fixed orifice) and subcooling (typically 10-15°F for TXV systems).
- Identify the four main components: evaporator, compressor, condenser, expansion device (TXV, piston, capillary tube).
- Understand that the compressor increases both pressure and temperature of the refrigerant vapor.
Field and Exam Application
- Measure superheat at the evaporator outlet: attach thermometer to suction line near the bulb, read suction pressure, convert to saturation temp, subtract from actual temp.
- Measure subcooling at the condenser outlet: attach thermometer to liquid line near the service valve, read liquid pressure, convert to saturation temp, subtract actual temp.
- Diagnose low refrigerant charge: high superheat, low subcooling, low suction pressure, high discharge temperature.
High-Yield Distinctions
- Superheat indicates how much heat the refrigerant has absorbed after boiling; low superheat risks liquid slugging. Subcooling indicates how much heat has been rejected after condensing; low subcooling indicates insufficient liquid in condenser.
- A TXV maintains constant superheat; a fixed orifice (piston) has variable superheat depending on load.
- The compressor is the heart of the system; it pumps refrigerant and creates pressure differential.
Common Pitfalls
- Confusing superheat and subcooling: superheat is for vapor, subcooling is for liquid.
- Using the wrong refrigerant P-T chart (e.g., using R-22 chart for R-410A).
- Assuming a system is fully charged based on sight glass alone; sight glass only indicates liquid line condition, not proper charge.
Review Tasks
- Plot the refrigeration cycle on a P-H diagram (pressure-enthalpy) and label each process.
- Practice calculating superheat and subcooling from given pressures and temperatures.
- Explain the function of each component in the cycle.
Air Distribution and Psychrometrics
Syllabus Focus
- Psychrometric properties (dry-bulb, wet-bulb, dew point, humidity ratio, enthalpy)
- Psychrometric chart reading
- Airflow measurement (CFM, velocity, static pressure)
- Duct design principles (friction loss, velocity, sizing)
- Ventilation requirements (ASHRAE 62.2, IMC)
Key Notes
- Psychrometrics: dry-bulb temperature is air temperature; wet-bulb is temperature with evaporative cooling; dew point is temperature at which moisture condenses. Humidity ratio is grains of moisture per pound of dry air.
- The psychrometric chart plots dry-bulb (x-axis) vs. humidity ratio (y-axis). Lines of constant wet-bulb, dew point, relative humidity, and enthalpy are shown.
- Airflow (CFM) = velocity (fpm) × duct area (sq ft). Measure velocity with an anemometer or pitot tube. Static pressure is resistance to airflow; measured with a manometer.
- Duct design: use friction loss charts (e.g., ACCA Manual D) to size ducts for given CFM and available static pressure. Typical friction loss: 0.1 in. w.c. per 100 ft.
- Ventilation: ASHRAE 62.2 requires mechanical ventilation for residences (e.g., 7.5 CFM per bedroom + 0.01 CFM per sq ft of conditioned floor area). IMC has similar requirements.
Must Know
- Read a psychrometric chart: find relative humidity given dry-bulb and wet-bulb temperatures.
- Calculate CFM from velocity and duct dimensions (e.g., 12x12 duct, velocity 800 fpm → CFM = 800 × 1 = 800).
- Understand static pressure: total external static pressure (TESP) is measured across the air handler; typical residential systems operate at 0.5 in. w.c.
- Know that supply air should be 15-20°F cooler than return air for cooling (sensible heat ratio).
Field and Exam Application
- Measure TESP: drill test holes in supply and return plenums, insert static pressure probe, read manometer. Compare to manufacturer's max (usually 0.5 in. w.c.).
- Use a psychrometric chart to determine if a space has high humidity: find dew point and compare to surface temperatures to predict condensation.
- Balance airflow in a multi-zone system: adjust dampers to achieve design CFM per zone using flow hood or traverse measurements.
High-Yield Distinctions
- Sensible heat changes dry-bulb temperature; latent heat changes moisture content (humidity ratio). Total heat = sensible + latent.
- Enthalpy is total heat content; used in load calculations and economizer control.
- Duct friction loss increases with velocity squared; doubling velocity quadruples friction loss.
Common Pitfalls
- Confusing wet-bulb and dew point: wet-bulb is measured with a wetted wick; dew point is calculated from dry-bulb and relative humidity.
- Using static pressure readings without correcting for altitude (manometer readings are in inches of water column; no correction needed for typical HVAC).
- Oversizing ducts: low velocity causes poor mixing and stratification; undersizing causes high static pressure and noise.
Review Tasks
- Plot a point on a psychrometric chart given dry-bulb 75°F and wet-bulb 65°F; find relative humidity and dew point.
- Calculate the required CFM for a 2000 sq ft house with 3 bedrooms using ASHRAE 62.2.
- Measure static pressure on a working system and compare to manufacturer specifications.
Gas Heating Systems and Combustion Analysis
Syllabus Focus
- Gas furnace components (burners, heat exchanger, gas valve, ignition system)
- Combustion process (stoichiometric, excess air, efficiency)
- Combustion analysis (O2, CO2, CO, stack temperature, draft)
- Safety controls (limit switches, flame rollout, pressure switches)
- Venting categories (B-vent, direct vent, power vent)
Key Notes
- Gas furnace: gas enters through gas valve, mixes with air in burners, ignites (spark or hot surface igniter), heats heat exchanger, combustion gases exit through flue. Blower circulates air over heat exchanger.
- Complete combustion: fuel + oxygen → CO2 + H2O + heat. Incomplete combustion produces CO (carbon monoxide). Excess air ensures complete combustion but reduces efficiency.
- Combustion analysis: measure O2 (target 4-9%), CO2 (target 6-9% for natural gas), CO (should be <100 ppm), stack temperature (higher = lower efficiency). Draft: negative pressure in flue (typically -0.02 to -0.04 in. w.c.).
- Safety controls: high-limit switch (opens on high temperature), flame rollout switch (detects flames outside burner), pressure switch (proves draft).
- Venting: Category I (natural draft, B-vent), Category III (positive pressure, sealed combustion), Category IV (high-efficiency, PVC vent).
Must Know
- Calculate combustion efficiency: efficiency = (1 - (stack temperature - room temperature) / (CO2% / 0.04)) × 100 (simplified).
- Identify and test a flame sensor: microamp output (typically 0.5-5 µA DC).
- Understand that a cracked heat exchanger can cause CO leakage; inspect with a mirror or CO detector.
- Know that gas pressure should be 3.5 in. w.c. for natural gas (manifold) and 11 in. w.c. for propane.
Field and Exam Application
- Perform combustion analysis: insert probe in flue, record O2, CO2, CO, stack temp, draft. Adjust air shutter to optimize O2 (e.g., 6% for natural gas).
- Diagnose a furnace that short cycles: check high-limit switch, airflow (dirty filter), or flame rollout switch.
- Test gas valve operation: measure voltage at valve (24V), check for gas flow with manometer.
High-Yield Distinctions
- Hot surface igniters (silicon carbide) are fragile; spark igniters are more durable but require proper gap.
- Condensing furnaces (90%+ AFUE) have secondary heat exchangers and PVC venting; non-condensing (80%) use metal B-vent.
- Excess air reduces efficiency but ensures safety; too little excess air causes CO production.
Common Pitfalls
- Confusing CO2 and CO: CO2 is a product of complete combustion; CO is a toxic byproduct of incomplete combustion.
- Forgetting to check for proper draft before combustion analysis; poor draft can cause false readings.
- Assuming a furnace is operating correctly if it heats; always perform combustion analysis to verify safety and efficiency.
Review Tasks
- List the steps for a combustion analysis on a natural gas furnace.
- Explain the function of a pressure switch and how to test it.
- Calculate the efficiency of a furnace with stack temp 350°F, room temp 70°F, CO2 8%.
Heat Pump Operation and Defrost Cycles
Syllabus Focus
- Heat pump cycle (reversing valve, check valves)
- Heating and cooling modes
- Defrost cycle initiation and termination
- Auxiliary/emergency heat
- Performance metrics (COP, HSPF, SEER)
Key Notes
- Heat pump: in cooling mode, operates like an air conditioner. In heating mode, reversing valve switches flow so condenser becomes evaporator (outdoor coil) and evaporator becomes condenser (indoor coil).
- Reversing valve: solenoid-operated; when energized, it shifts the valve to reverse flow. Check valves (or expansion devices) ensure proper refrigerant flow in both modes.
- Defrost cycle: when outdoor coil temperature drops below freezing (typically 32°F), frost accumulates. Defrost is initiated by a timer (e.g., 30, 60, 90 minutes) or a temperature sensor (e.g., 28°F). During defrost, the reversing valve switches to cooling mode (outdoor coil becomes condenser), and the outdoor fan stops. Defrost terminates when coil temperature reaches about 60°F or after a maximum time (e.g., 10 minutes).
- Auxiliary heat (electric resistance or gas) supplements heat pump when outdoor temperature is very low or during defrost. Emergency heat locks out heat pump and uses only auxiliary heat.
- COP (Coefficient of Performance) = heat output / electrical input. HSPF (Heating Seasonal Performance Factor) is seasonal efficiency. SEER (Seasonal Energy Efficiency Ratio) is cooling efficiency.
Must Know
- Identify reversing valve operation: 24V solenoid; when energized, valve shifts. Listen for a click or feel for temperature change at lines.
- Understand defrost control board: typically has timer and temperature sensor. Test by jumping terminals or using a magnet on a reed switch.
- Know that auxiliary heat should come on during defrost to prevent cold air from supply vents.
- Calculate COP: e.g., 3.5 kW heat output from 1 kW input = COP 3.5.
Field and Exam Application
- Diagnose a heat pump that blows cold air in heating mode: check reversing valve (stuck or failed solenoid), check defrost control, or low refrigerant.
- Test defrost cycle: force defrost by shorting test pins on control board; observe outdoor fan stop, compressor run, and auxiliary heat engage.
- Measure temperature difference across indoor coil in heating mode: should be 15-20°F (supply minus return).
High-Yield Distinctions
- In heating mode, the outdoor coil is the evaporator (cold); in cooling mode, it is the condenser (hot).
- Defrost is necessary because ice insulates the coil and reduces heat transfer; defrost melts ice using heat from the indoor space.
- Auxiliary heat is less efficient than heat pump; emergency heat should only be used if heat pump fails.
Common Pitfalls
- Confusing auxiliary heat and emergency heat: auxiliary operates automatically; emergency is manually selected.
- Thinking a heat pump is inefficient in cold climates; modern cold-climate heat pumps can operate down to -13°F.
- Forgetting to check defrost termination sensor; if stuck closed, defrost may run too long or not at all.
Review Tasks
- Trace the refrigerant flow in heating mode and cooling mode on a diagram.
- Explain the defrost cycle initiation and termination methods.
- Calculate COP for a heat pump that delivers 36,000 BTU/h with 3.5 kW input (1 kW = 3412 BTU/h).
System Installation, Maintenance, and EPA Compliance
Syllabus Focus
- Installation best practices (refrigerant piping, electrical, ductwork)
- Preventive maintenance (cleaning coils, filters, checking charge)
- EPA Section 608 requirements (refrigerant handling, recovery, recycling)
- Safety (lockout/tagout, PPE, refrigerant safety)
- Codes and standards (IMC, NEC, local codes)
Key Notes
- Installation: refrigerant lines must be clean, dry, and leak-free. Use nitrogen pressure test (150-200 psi) and vacuum (500 microns or less). Electrical connections must comply with NEC (wire sizing, overcurrent protection, disconnect). Ductwork should be sealed and insulated per IMC.
- Preventive maintenance: clean condenser coils annually, replace filters monthly, check refrigerant charge (superheat/subcooling), inspect electrical connections, lubricate motors if applicable.
- EPA Section 608: technicians must be certified to handle refrigerants. Types I (small appliances), II (high-pressure), III (low-pressure), Universal. Recovery equipment must meet EPA standards. Refrigerant cannot be vented; must be recovered and recycled or reclaimed.
- Safety: use lockout/tagout when servicing electrical equipment. Wear PPE (gloves, safety glasses). Refrigerants can cause frostbite or asphyxiation; work in ventilated areas.
- Codes: IMC covers mechanical systems; NEC covers electrical; local codes may have additional requirements (e.g., seismic bracing, flood zones).
Must Know
- Perform a proper evacuation: pull vacuum to 500 microns, hold for 15 minutes (no rise).
- Identify EPA Section 608 certification types: Type I (small appliances), Type II (high-pressure), Type III (low-pressure), Universal (all).
- Know that R-22 is being phased out; production and import ended in 2020. R-410A is common in new systems.
- Understand that refrigerant recovery is required before servicing or disposing of equipment.
Field and Exam Application
- Install a new split system: run line set, braze with nitrogen flow, pressure test, evacuate, charge by weight or superheat/subcooling.
- Perform annual maintenance: clean outdoor coil with coil cleaner, check capacitor, measure amp draw, verify charge.
- Recover refrigerant from a system: connect recovery machine, recover to appropriate cylinder, weigh recovered amount.
High-Yield Distinctions
- Recovery removes refrigerant from system; recycling cleans refrigerant for reuse; reclamation returns refrigerant to original purity.
- Vacuum level: 500 microns is acceptable; lower is better. A rise above 1000 microns indicates a leak or moisture.
- EPA prohibits venting any refrigerant, including substitutes like R-410A and R-134a.
Common Pitfalls
- Skipping nitrogen flow during brazing: causes internal oxidation and contamination.
- Not recovering refrigerant before opening system: illegal and harmful to environment.
- Using incorrect vacuum pump oil (must be vacuum pump oil, not motor oil).
Review Tasks
- List the steps for a proper system evacuation.
- Explain the difference between recovery, recycling, and reclamation.
- Identify the required PPE for handling refrigerants.
How To Use These Notes With Practice Questions
Do not jump straight from reading to a full mock. Work by subject first: review the key notes, make a short recall sheet from memory, then answer a focused question set. After each miss, decide whether the problem was missing theory, weak code/source recall, poor measurement setup, calculation error, or a field sequence you did not visualize.
Technical Conquer's question bank, flashcards, mind maps, and spaced review tools are most useful after this instruction layer because they reveal which parts of the notes are not yet retrievable.
Final Review Checklist
- Review all six subjects, focusing on must-know items and high-yield distinctions.
- Practice using a P-T chart and psychrometric chart until comfortable.
- Understand the refrigeration cycle and heat pump cycle thoroughly.
- Be familiar with combustion analysis and gas furnace safety controls.
- Know EPA Section 608 requirements and proper installation/maintenance procedures.
- Take practice exams to identify weak areas and review corresponding notes.
- Verify exam details (format, pass mark, eligibility) with HVAC Excellence or ESCO Institute.
Official Sources and Further Reading
Use these sources as the final authority for format, eligibility, rules, regulatory limits, and exam updates. Study notes are a preparation layer, not a replacement for official candidate guidance.